Cu+-containing materials have drawn much attention in various applications because they are versatile, nontoxic, and low-cost. However, the difficulty of selective reduction and the poor stability of Cu+ species are now pretty much the agendas. Here, controlled construction of supported Cu+ sites in MIL-100(Fe) was realized under mild conditions (200 °C, 5 h) via a vapor-reduction strategy (VRS). Remarkably, the yield of Cu+ reaches 100%, which is quite higher than the traditional high-temperature autoreduction method with a yield less than 50% even at 700 °C for 12 h. More importantly, during the treatment via VRS some Fe3+ in MIL-100(Fe) are reduced to Fe2+, which prevent the frequently happened oxidation of Cu+ due to the higher oxidation potential of Fe2+. These properties make Cu+/MIL-100(Fe) efficient in the capture of typical aromatic sulfur, benzothiophene, with regard to both adsorption capacity and stability. To our knowledge, the stabilization of Cu+ using the oxidation tendency of supports is achieved for the first time, which may offer a new idea to utilize active sites with weak stability.Keywords: adsorbents; desulfurization; metal−organic frameworks; stabilization; supported cuprous sites;

Great attention has been given to metal–organic frameworks (MOFs)-derived solid bases because of their attractive structure and catalytic performance in various organic reactions. The extraordinary skeleton structure of MOFs provides many possibilities for incorporation of diverse basic functionalities, which is unachievable for conventional solid bases. The past decade has witnessed remarkable advances in this vibrant research area; however, MOFs for heterogeneous basic catalysis have never been reviewed until now. Therefore, a review summarizing MOFs-derived base catalysts is highly expected. In this review, we present an overview of the recent progress in MOFs-derived solid bases covering preparation, characterization, and catalytic applications. In the preparation section, the solid bases are divided into two categories, namely, MOFs with intrinsic basicity and MOFs with modified basicity. The basicity can originate from either metal sites or organic ligands. Different approaches used for generation of basic sites are included, and each approach is described with representative examples. The fundamental principles for the design and fabrication of MOFs with basic functionalities are featured. In the characterization section, experimental techniques and theoretical calculations employed for characterization of basic MOFs are summarized. Some representive experimental techniques, such as temperature-programmed desorption of CO2 (CO2-TPD) and infrared (IR) spectra of different probing molecules, are covered. Following preparation and characterization, the catalytic applications of MOFs-derived solid bases are dealt with. These solid bases have potential to catalyze some well-known “base-catalyzed reactions” like Knoevenagel condensation, aldol condensation, and Michael addition. Meanwhile, in contrast to conventional solid bases, MOFs show some different catalytic properties due to their special structural and surface properties. Remarkably, characteristic features of MOFs-derived solid bases are described by comparing with conventional inorganic counterparts, keeping in mind the current opportunities and challenges in this field.

Poor dispersity and low stability are two predominant shortcomings hindering the applications of metal–organic polyhedra (MOPs). The confinement of MOPs in nanoscale cavities of mesoporous matrices is efficient in overcoming both shortcomings, while the improvement of the current double-solvent method is highly expected. Here we develop a facile, controllable strategy to fabricate three MOPs (coordinated from dicopper and carboxylates) in confined cavities via in situ site-induced assembly (SIA), for the first time. The cavities of mesoporous matrix SBA-16 were pre-functionalized with amine sites, which induce in situ assembly of precursors that diffused into cavities. Hence, both the amount and location of MOPs in the mesoporous matrix can be easily controlled. Upon confinement, the dispersity, stability, and catalytic performance (on ring-opening reactions) of MOPs are greatly improved. Moreover, the enhancement of stability makes it possible to observe MOPs using high-resolution transmission electron microscopy (HRTEM) directly.

A smart adsorbent RA@MS is fabricated by incorporating a di-block copolymer through the combination of the thermo-responsive block poly(N-isopropylacrylamide) (R) and the active block poly{N-[3-(dimethylamino) propyl]methacrylamide} (A, tertiary amines as basic sites) into mesoporous silica. The di-block copolymer RA preserves the thermo-responsive nature, which makes the active sites reversibly exposed/blocked in light of temperature variation. The obtained adsorbent possessing thermo-responsive properties can thus realize both selective adsorption and efficient regeneration for temperature-swing adsorption (TSA) of dyes.

•The confined space hinders the aggregation of Au and retains the catalytic activity.•The SPR strategy avoids the competitive adsorption of solvent molecules with guests.•Highly dispersed Au species are highly active for catalytic reduction reactions.•The template favors the dispersion of Au and the enhancement of catalytic activity.Au-containing catalysts are highly active in diverse reactions, and their activity strongly depends on the dispersion degree of Au. Here we report for the first time a solid-phase reduction strategy to promote Au dispersion in template-occluded SBA-15 (AS) by fully considering three crucial factors, namely (i) the interaction between Au and supports, (ii) the space where Au precursors locate during reduction, and (iii) the reduction method. First, both template and silica walls in AS offer interaction with Au species. Second, AS presents confined spaces between template and silica walls. Third, the reduction in solid phase avoids the competitive adsorption of solvent molecules. The results show Au-containing AS has a better dispersion of Au than its counterpart prepared from template-free SBA-15 (CS). Moreover, the obtained materials exhibit excellent catalytic activity in reduction reactions and that the organic template retained in mesopores promotes the reactions greatly.Download high-res image (200KB)Download full-size image

Owing to their high physicochemical stability, low skeletal density, tailorable surface properties, and high porosity, microporous crosslink polymers are highly promising for selective CO2 capture, separation, and storage. The crosslinking (CL) and crosslinker length (CLL) in a polymer play a quite significant role in enhancing selective CO2 capture. To investigate the role of CL and CLL, polymers with no crosslinking (non-crosslinking, NCL), and small-(SCL), and long-crosslinker lengths (LCL) were successfully fabricated. It is noteworthy that the polymer containing SCL has remarkable CO2 adsorption capacity and selectivity over the polymer with LCL and NCL. High selectivity for CO2 over CH4/N2 was observed in the sequence SCL > LCL > NCL. This indicates that not only CL but CLL is also significantly important in generating highly efficient adsorbents. The adsorption capacity reaches 208.3 mg g−1, which is higher than that of the benchmarks including activated carbon (122.8 mg g−1), and 13X zeolite (180.3 mg g−1), as well as most reported carbon-based adsorbents. The CO2/N2 and CO2/CH4 selectivity reaches 541.4 and 64, respectively. Moreover, excellent recyclability was observed without loss in CO2 adsorption for 10 cycles. Thus, high CO2 capture, excellent selectivity, and high recyclability under energy-saving mild regeneration conditions make microporous polymers a unique adsorbent for selective CO2 capture from flue gas and natural gas.

Metal–organic polyhedra (MOPs) have attracted great attention due to their intriguing structure. However, the applications of MOPs are severely hindered by two shortcomings, namely low dispersity and poor stability. Here we report the introduction of four MOPs (constructed from dicopper and carboxylates) to cavity-structured mesoporous silica SBA-16 via a double-solvent strategy to overcome both shortcomings simultaneously. By judicious design, the dimension of MOPs is just between the size of cavities and entrances of SBA-16, MOP molecules are thus confined in the cavities. This leads to the formation of isolated MOPs with unusual dispersion, making the active sites highly accessible. Hence, the adsorption capacity on carbon dioxide and propene as well as catalytic performance on ring opening are much superior to bulk MOPs. More importantly, the structure and catalytic activity of MOPs in confined cavities are well preserved after exposure to humid atmosphere, whereas those of bulk MOPs are degraded seriously.

Functionalization of metal–organic frameworks (MOFs) with Cu(I) sites is extremely desirable for various applications including adsorption, catalysis, and sensing. The traditional method for the conversion of supported Cu(II) to Cu(I) is high-temperature autoreduction (HTA), which produces Cu(I) with an unsatisfactory yield (ca. 50%) but requires quite harsh conditions (e.g. 700 °C, 12 h) that are unsuitable for MOFs. Here we report the rational design of an efficient, controllable strategy for the conversion of supported Cu(II) to Cu(I) by using vapor-induced selective reduction (VISR), in which vapors of weak reducing agents (e.g. methanol) diffuse into the pores of MOFs and interact with Cu(II) precursors. This strategy allows the fabrication of Cu(I) sites with a 100% yield without the formation of Cu(0) at much lower temperatures (e.g. 200 °C, 6 h) and subsequently preserves the structure of MOFs well. Due to the abundant Cu(I) sites and high porosity of MOF supports, the obtained materials exhibit excellent performance in adsorptive desulfurization with regard to capacity, selectivity, and recyclability.

Selective adsorption and efficient regeneration are two crucial issues for adsorption processes; unfortunately, only one of them instead of both is favored by traditional adsorbents with fixed pore orifices. Herein, we fabricated a new generation of smart adsorbents through grafting photoresponsive molecules, namely, 4-(3-triethoxysilylpropyl-ureido)azobenzene (AB-TPI), onto pore orifices of the support mesoporous silica. The azobenzene (AB) derivatives serve as the molecular gates of mesopores and are reversibly opened and closed upon light irradiation. Irradiation with visible light (450 nm) causes AB molecules to isomerize from cis to trans configuration, and the molecular gates are closed. It is easy for smaller adsorbates to enter while difficult for the larger ones, and the selective adsorption is consequently facilitated. Upon irradiation with UV light (365 nm), the AB molecules are transformed from trans to cis isomers, promoting the desorption of adsorbates due to the opened molecular gates. The present smart adsorbents can consequently benefit not only selective adsorption but also efficient desorption, which are exceedingly desirable for adsorptive separation but impossible for traditional adsorbents with fixed pore orifices.Keywords: efficient regeneration; molecular gates; photoresponsive property; selective adsorption; smart adsorbents

Much attention has been paid to metal–organic frameworks (MOFs) due to their large surface areas, tunable functionality, and diverse structure. Nevertheless, most reported MOFs show poor hydrothermal stability, which seriously hinders their applications. Here a strategy is adopted to tailor the properties of MOFs by means of incorporating carboxyl-functionalized natural clay attapulgite (ATP) into HKUST-1, a well-known MOF. A new type of hybrid material was thus fabricated from the hybridization of HKUST-1 and ATP. Our results indicated that the hydrothermal stability of the MOFs as well as the catalytic performance was apparently improved. The frameworks of HKUST-1 were severely destroyed after hydrothermal treatment (hot water vapor, 60 °C), while that of the hybrid materials was maintained. For the hybrid materials containing 8.4 wt % of ATP, the surface area reached 1302 m2·g–1 and was even higher than that of pristine HKUST-1 (1245 m2·g–1). In the ring-opening of styrene oxide, the conversion reached 98.9% at only 20 min under catalysis from the hybrid material, which was obviously higher than that over pristine HKUST-1 (80.9%). Moreover, the hybrid materials showed excellent reusability and the catalytic activity was recoverable without loss after six cycles. Our materials provide promising candidates for heterogeneous catalysis owing to the good catalytic activity and reusability.

A new generation of smart adsorbents was designed by grafting photo-responsive molecules onto the pore entrances of mesoporous silica. These molecules act as the gates of the mesopores, which are reversibly closed/opened upon light irradiation. Our smart adsorbents thus realize both selective adsorption and efficient desorption, which is highly expected for adsorption but impossible for traditional adsorbents with fixed pore entrances.

Silver (Ag)-based nanoparticles are one type of highly effective antimicrobial widely used in medical devices, consumer products, and wound dressing. Although Ag(I) rather than Ag(0) is the active species in antibacterial processes, the use of Ag(I) as antibacterial materials is hindered by its instability toward light irradiation. In this paper, we report the fabrication of core–shell AgCl@SiO2 nanoparticles, which comprise a core of AgCl nanoparticles and a shell of porous silica, for antibacterial applications for the first time. The porous silica shells not only enhance the stability of AgCl by preventing the core from direct light irradiation but also allow active Ag(I) to pass through continuously to inhibit the growth of bacteria. It is worth noting that the synthesis is achieved by a facile one-pot method in which the surfactant hexadecyltrimethylammonium chloride used for the formation of AgCl nanoparticles also acts as a structure-directing agent in the subsequent creation of porous silica. Our results show that the obtained AgCl@SiO2 nanoparticles exhibit well-defined core–shell structure and are highly efficient in the growth inhibition of Escherichia coli. More importantly, the stability of Ag(I) toward light irradiation is greatly enhanced by the protection of the silica shell. The convenient fabrication, well-defined core–shell structure, and enhanced stability make AgCl@SiO2 nanoparticles highly promising for antibacterial applications.Keywords: Antibacterial materials; Light stability; One-pot synthesis; Porous silica shell; Silver chloride nanoparticles

Elimination of aromatic sulfur and nitrogen compounds via selective adsorption is an effective method for the purification of transportation fuels to meet the increasingly stringent environmental requirements. Since the adsorption processes proceed in liquid phases, separation and recycling of adsorbents should be greatly facilitated if they were endowed with magnetism. In the present study, magnetically responsive core–shell microspheres, Fe3O4@C, which comprise a magnetite core and a carbon shell with a thickness adjustable from 47 to 97 nm, were fabricated for the adsorption of aromatic sulfur and nitrogen compounds. The carbon shell derived from the carbonization of a resorcinol–formaldehyde polymer possesses abundant porosity with a hierarchical structure, which is highly active in the capture of aromatic sulfur and nitrogen compounds despite the absence of any active metal sites such as Cu(I) and Ag(I). Our results show that the Fe3O4@C adsorbents with BET surface areas ranging from 227 to 264 m2 g–1 are capable of removing thiophene (0.483 mmol g–1), benzothiophene (0.476 mmol g–1), indole (0.463 mmol g–1), and quinolone (0.297 mmol g–1) efficiently under ambient conditions. More importantly, the superparamagnetism allows the adsorbents to be separated conveniently from the adsorption system by the use of an external field. The regenerated adsorbents after six cycles still exhibit a good adsorption capacity comparable to that of the fresh one. The present magnetically responsive core–shell Fe3O4@C adsorbents with low cost, high efficiency, and convenient recycling make them highly promising in the purification of transportation fuels.Keywords: Carbon; Core−shell microspheres; Denitrogenation; Desulfurization; Magnetically responsive adsorbents; Regeneration;

Adsorption and desorption are equally important in an adsorptive separation process, while conventional adsorbents with fixed pores benefit only one of them rather than both. Here, a new generation of adsorbents was fabricated by incorporating thermo-responsive polymers (TRPs) into pores. The TRPs act as molecular switches, making pore spaces and active sites responsive to adsorption/desorption conditions. The adsorbents can thus realize both selective adsorption and efficient desorption, which are extremely desirable for adsorptive separation.

Fabrication of bifunctional Cu(I)/Ce(IV) sites in mesoporous silica SBA-15 requires a series of complicated steps, including introduction of the Ce(III) precursor, calcination to generate Ce(IV), further introduction of the Cu(II) precursor, and repeated calcination to generate Cu(I). This traditional method has low efficiency and wastes energy. Here we provide a highly efficient, convenient and green strategy for the fabrication of bifunctional Cu(I)/Ce(IV) sites in mesoporous silica SBA-15, for the first time. The precursors CuCl2 and CeCl3 were simultaneously introduced into SBA-15. Based on a guests-redox strategy, both the reduction of CuCl2 to CuCl and the oxidation of CeCl3 to CeO2 could be realized in one calcination step. This strategy avoids the repeated modification process, and guarantees a high Cu(I) yield of ∼59% without generation of toxic gas. In addition, the resultant materials show excellent performance in gas separation of C2H4 from C2H6.

Because of their abundant porosity, tunable surface properties, and high stability, N-doped porous carbons (NPCs) are highly promising for CO2 capture. Carbonization of N-containing polymers is frequently used for the preparation of NPCs, while such an approach is hindered by the high cost of some polymer precursors. In the present study, we report for the first time the fabrication of NPCs through the rational choice of the low-cost, N-rich polymer NUT-2 (NUT indicates Nanjing Tech University) as the precursor, which was obtained from polymerization of easily available monomers under mild conditions in the absence of any catalysts. Through carbonization at different temperatures (500–800 °C), NPCs with various porosity and nitrogen contents are obtained. The pore structure and CO2-philic (N-doped) sites are responsible for the adsorption performance, while the highest surface area does not lead to the highest CO2 adsorption capacity. For the sample carbonized at 600 °C (NPC-2-600), the adsorption capacity on CO2 is as high as 164.7 cm3 g–1 at 0 °C and 1 bar, which is much better than that of the benchmarks, such as activated carbon (62.5 cm3 g–1) and 13X zeolite (91.8 cm3 g–1), as well as most reported carbon-based adsorbents. We also demonstrate that the present NPCs can be regenerated completely under mild conditions. The present adsorbents may provide promising candidates for the capture of CO2 from various mixtures, such as flue gas and natural gas.

Mesoporous solid bases are extremely desirable in green catalytic processes, due to their advantages of accelerated mass transport, negligible corrosion, and easy separation. Great progress has been made in mesoporous solid bases in the last decade. In addition to their wide applications in the catalytic synthesis of organics and fine chemicals, mesoporous solid bases have also been used in the field of energy and environmental catalysis. Development of mesoporous solid bases is therefore of significant importance from both academic and practical points of view. In this review, we provide an overview of the recent advances in mesoporous solid bases, which is basically grouped by the support type and each category is illustrated with typical examples. Cooperative catalysts derived from the incorporation of additional functionalities (i.e. acid and metal) into mesoporous solid bases are also included. The fundamental principles of how to design and fabricate basic materials with mesostructure are highlighted. The mechanism of the formation of basic sites in different mesoporous systems is discussed as well.

Due to their synthetic diversification, low skeletal density, and high physicochemical stability, porous polymer networks (PPNs) are highly promising in a variety of applications such as carbon capture. Nevertheless, complicated monomers and/or expensive catalysts are normally utilized for their synthesis, which makes the process tedious, costly, and hard to scale up. In this study, a facile nucleophilic substitution reaction was designed to fabricate PPNs from low-cost monomers, namely chloromethyl benzene and ethylene diamine. A surfactant template was also used to direct the assembly, leading to the formation of PPN with enhanced porosity. It is fascinating that the polymerization reactions can occur at the low temperature of 63 °C in the absence of any catalyst. The obtained PPNs contain abundant secondary amines, which offer appropriate adsorbate–adsorbent interactions from the viewpoints of selective CO2 capture and energy-efficient regeneration of the adsorbents. Hence, these PPNs are highly active in selective adsorption of CO2, and unusually high CO2/N2 and CO2/CH4 selectivity was obtained. Moreover, the PPN adsorbents can be completely regenerated under mild conditions.

Metal–organic frameworks (MOFs) have attracted extensive attention due to their large surface area, diverse structures, and tuneable functionality. However, the poor hydrostability of most reported MOFs hinders their practical applications severely. In this paper, we report a strategy to modulate the properties of a typical MOF, namely MOF-5 [Zn4O(BDC)3; BDC = 1,4-benzenedicarboxylate] by hybridizing it with a natural clay (i.e. attapulgite), for the first time. A new kind of hybrid material resulting from the hybridization of the MOF and attapulgite was thus constructed. Our results showed that the hydrostability of the MOF was apparently improved due to the hybridization with attapulgite. The frameworks of MOF-5 were degraded seriously under the humid atmosphere, while the structure of the hybrid materials could be well preserved. We also demonstrated that the hybrid materials were highly active in the heterogeneous Friedel–Crafts alkylation reaction of benzyl bromide with toluene. The conversion of benzyl bromide reached ∼100% under the reaction conditions investigated. More importantly, the catalytic stability of the hybrid materials was significantly enhanced owing to the introduction of attapulgite. The activity could be well recovered with no detectable loss, and the conversion remained at ∼100% at the sixth run, which was apparently higher than that of MOF-5 (27.7% at the sixth run). The excellent hydrostability, catalytic activity, and reusability make the present materials highly promising for utilization as heterogeneous catalysts in practical applications.

Due to their versatility, nontoxicity, and low cost, Cu(I) ion exchanged zeolites are of great interest for various applications. Despite many attempts, the development of an efficient, controllable, and energy-saving approach to fabricate Cu(I) sites in zeolites remains an open question. In this study, a strategy was developed to convert Cu(II) in zeolites to Cu(I) selectively using vapor-induced reduction (VIR) with methanol. The methanol vapors generated at elevated temperatures diffuse into the pores of zeolites and interact with Cu(II) ions, leading to the formation of Cu(I). This strategy allows the construction of Cu(I) sites at low temperatures and avoids the formation of Cu(0). Moreover, the obtained material exhibits excellent performance in the adsorptive separation of propylene/propane with regard to both capacity and selectivity, which is obviously superior to the material prepared by the conventional autoreduction method as well as using various typical adsorbents.

A redox strategy was designed to generate strong basicity on mesoporous silica by using the redox interaction of a precursor with methanol vapor. The formation of strongly basic sites was realized at 400 °C, which breaks the tradition of thermally induced decomposition that usually requires much higher temperatures (>600 °C).

Owing to their high physicochemical stability and low skeleton density, polymers are highly promising for capturing the greenhouse gas CO2. However, complicated monomers, expensive catalysts, and/or severe conditions are usually required for their synthesis, which makes the process costly, tedious, and hard to scale up. In this paper, a facile nucleophilic substitution reaction is developed to synthesize polymers from low-cost monomers, namely chloromethylbenzene and various diamines. Due to the appropriate reactivity of monomers, the polymerization takes place at a low temperature of about 60 °C in the absence of any catalysts. A series of polymers containing plentiful secondary amines are successfully fabricated; these secondary amines provide a proper adsorbate–adsorbent interaction from the viewpoints of selective capture of CO2 and energy-efficient regeneration of adsorbents. Moreover, the materials possess well-defined micropores with the dimension close to the size of adsorbate molecules and subsequently, exhibit the molecule sieving effect. As a result, these materials are active in selective adsorption of CO2 and show high CO2/N2 and CO2/CH4 selectivities. More importantly, the adsorbents can be completely regenerated under mild conditions, and no loss in activity is detected after eight cycles.Keywords: CO2 capture; Energy-saving regeneration; Polymer; Secondary amine; Selective adsorption

Metal–organic frameworks (MOFs) show high potential in adsorptive removal of aromatic sulfur compounds; however, the crucial factors affecting the adsorption performances are scarcely clarified. In the present study, three classic aromatic sulfur compounds (i.e., thiophene, benzothiophene, and 4,6-dimethyldibenzothiophene) as well as five typical MOFs (i.e., MOF-5, HKUST-1, MIL-53(Fe), MIL-53(Cr), and MIL-101(Cr)) were selected for study. The adsorptive desulfurization performances of MOFs were investigated by using a fixed-bed adsorption system. In the case of thiophene, the adsorption capacity of MOFs decreases in the order MIL-53(Cr) > HKUST-1 > MOF-5 > MIL-53(Fe) > MIL-101(Cr). For the first time, the adsorbate–adsorbent interaction was examined in detail by using infrared spectra and temperature-programmed desorption. Such an interaction was demonstrated to be the most important factor affecting adsorption performance. When the molecular size of aromatic sulfur compounds is comparable to or smaller than the window diameter of MOFs, the influence of window diameter becomes apparent. It is surprising to find that the adsorbate–adsorbent interaction plays a major role, which is responsible for the poor adsorption performance of MIL-101(Cr) with quite high porosity. Therefore, metal sites and structure that contribute to the adsorbate–adsorbent interaction should be considered to be the most significant factor aiming to develop new MOFs for adsorptive desulfurization.

Homogeneous dual-ligand zinc complex catalysts was developed for the synthesis of propylene carbonate (PC) through chemical fixation of CO2. It was found that among a number of various pKa N-donor ligands, the catalytic performance was enhanced dramatically and the corrosion of the reaction system was effectively inhibited when 1-methylimidazol (1MI) was used as the N-donor ligand, in which >90 % PC yield could be obtained under mild reaction conditions. The dual-ligand zinc complex catalysts were characterized by various spectroscopic techniques such as FT-IR and 1HNMR. X-ray crystallography showed that the Zn(II) atom was coordinated in tetrahedron geometry by three bromine atom, one 1MI nitrogen atom, and one crystallographically independent cation to give a 3D tetrahedron structure, which forms tetracoordinated complexes. The structure of the complex gives the reasons for the enhancement of the catalytic activity from the microscopic molecular structure point of an extremely long and therefore labile Zn–Br bond, the diversification of the bond angles, and the interplay between the steric hindrance, which have great influence on the interaction forces of Zn–Br.

Deep desulfurization of transportation fuels via π-complexation adsorption is an effective method for the selective capture of aromatic sulfur compounds. Taking into consideration that the desulfurization of transportation fuels proceeds in the liquid phase, separation and recycling of adsorbents should be greatly facilitated if the adsorbents were endowed with magnetism. In this paper, magnetically responsive core–shell π-complexation adsorbent microspheres, AgNO3/Fe3O4@mSiO2 (mSiO2 denotes mesoporous silica), which comprises a core of magnetite particles and a shell of mesoporous silica dispersed with AgNO3, was developed for the first time. The silica shell exhibits highly open mesopores with perpendicularly aligned pore channels, large surface area (694 m2 g−1) and uniform pore size (2.3 nm), which is quite beneficial to the accommodation of Ag(I) active species. As a result, AgNO3 can be well dispersed in the pores of silica shells and are highly accessible to adsorbate molecules. Our results show that the adsorbent is active in the adsorptive removal of a typical aromatic sulfur compound, thiophene, via π-complexation under ambient conditions. More importantly, the superparamagnetism allows the adsorbent to be separated conveniently from the adsorption system in several seconds by the use of an external field. After desulfurization, the adsorbents were regenerated by washing with isooctane and subsequent thermal dispersion in Ar. The regenerated adsorbent after six cycles still shows a good adsorption capacity (0.145 mmol g−1 or 4.64 mg g−1), which is comparable to the fresh adsorbent (0.147 mmol g−1 or 4.70 mg g−1). The magnetically responsive π-complexation adsorbent may be a promising candidate for the deep purification of transportation fuels.

Porous polymer networks have great potential in various applications including carbon capture. However, complex monomers and/or expensive catalysts are commonly used for their synthesis, which makes the process complicated, costly, and hard to scale up. Herein, we develop a molecular template strategy to fabricate new porous polymer networks by a simple nucleophilic substitution reaction of two low-cost monomers (i.e., chloromethylbenzene and ethylene diamine). The polymerization reactions can take place under mild conditions in the absence of any catalysts. The resultant materials are interconnected with secondary amines and show well-defined micropores due to the structure-directing role of solvent molecules. These properties make our materials highly efficient for selective CO2 capture, and unusually high CO2/N2 and CO2/CH4 selectivities are obtained. Furthermore, the adsorbents can be completely regenerated under mild conditions. Our materials may provide promising candidates for selective capture of CO2 from mixtures such as flue gas and natural gas.Keywords: CO2 capture; molecular template; porous polymer networks; regeneration; selectivity

New solid strong bases were fabricated at room temperature by grafting lithium-containing molecular precursors onto β-cyclodextrin. The solid bases show strong basicity with a molecular-level dispersion of lithium sites, which are highly active in transesterification reactions and impossible to realize through the traditional high-temperature method.

Template-derived carbon is demonstrated to effectively promote the creation of strong basicity on mesoporous silica, for the first time. New materials owning ordered mesoporous structure, strong basicity, and excellent catalytic activity are thus successfully constructed at low temperatures, which are impossible to achieve using conventional methods.

This paper aims to improve the hydrothermal stability and catalytic activity of metal–organic frameworks (MOFs), which are believed to play an important role in the practical applications of MOFs in catalysis. Our strategy is to incorporate graphite oxide into a typical MOF, namely HKUST-1 (Cu3(BTC)2, BTC = 1,3,5-benzenetricarboxylic acid; HKUST = Hong Kong University of Science and Technology), and the properties of MOF are successfully tailored by use of this strategy. The obtained MOF/graphite oxide composites show enhanced porosity with high surface areas and some meso/macropores. For the composite containing 8.7 wt % of graphite oxide, the surface area reaches 1257 m2 g–1, which is obviously higher than pure HKUST-1 (841 m2 g–1). The pore structure of composites favors the access of reactant molecules to active sites and accelerates mass transfer in channels. Furthermore, the incorporation of graphite oxide creates a more hydrophobic environment surrounding metallic sites, which prevents the coordination bonds from attacking by water molecules and presents better affinity of active sites to organic reactants. Hence, the hydrothermal stability of MOF as well as the catalytic performance with regard to both activity and reaction rate are greatly improved. For the composite incorporating 8.7 wt % of graphite oxide, the conversion of styrene oxide in the ring-opening reaction can reach 74.1% after reaction for only 20 min, which is much higher than pure HKUST-1 (10.7%). More importantly, the catalytic activity can be well recovered without any loss even after six cycles. The excellent hydrothermal stability, catalytic activity, and reusability make our materials highly promising for use as heterogeneous catalysts in practical applications.

•DGC is developed to synthesize magnetically responsive MOF/Fe3O4 composites.•DGC simplifies synthetic procedures and minimizes solvent consumption.•The composites are used for adsorption desulfurization and denitrogenation.•The composites can be recycled efficiently by an external magnetic field.Selective adsorption by use of metal-organic frameworks (MOFs) is an effective method for purification of hydrocarbon fuels. In consideration that the adsorption processes proceed in liquid phases, separation and recycling of adsorbents should be greatly facilitated if MOFs were endowed with magnetism. In the present study, we reported for the first time a dry gel conversion (DGC) strategy to fabricate magnetically responsive MOFs as adsorbents for deep desulfurization and denitrogenation. The solvent is separated from the solid materials in the DGC strategy, and vapor is generated at elevated temperatures to induce the growth of MOFs around magnetic Fe3O4 nanoparticles. This strategy can greatly simplify the complicated procedures of the well-known layer-by-layer method and avoid the blockage of pores confronted by introducing magnetic Fe3O4 nanoparticles to the pores of MOFs. Our results show that the adsorbents are capable of efficiently removing aromatic sulfur and nitrogen compounds from model fuels, for example removing 0.62 mmol g−1 S and 0.89 mmol g−1 N of thiophene and indole, respectively. In addition, the adsorbents are facile to separate from liquid phases by use of an external field. After 6 cycles, the adsorbents still show a good adsorption capacity that is comparable to the fresh one.

•We first develop periodic mesoporous organosilicas based on the framework of amino acid.•A novel amino acid bridged organosilane based on aspartic acid is prepared.•Ordered 2D mesoporous structure is formed in the aspartic acid bridged PMOs materials.Novel periodic mesoporous organosilicas materials (PMOs) based on the flexible skeleton of aspartic acid were synthesized by the co-condensation of aspartic acid-bridged organosilane (Asp-BOSP) and tetraethyl orthosilicate (TEOS) in an acidic medium, using the Pluronic P123 surfactant as a template. Furthermore, a new amino acid organosilane was developed by the simple reaction between traditional organosilicone ((3-aminopropyl) trimethoxysilane) and aspartic acid. The small-angle XRD and N2 adsorption-desorption isotherms demonstrate that these PMOs materials possess ordered 2D hexagonal mesostructures in the region of low molar concentrations of Asp-BOSP (⩽10%). Analysis of FTIR and 29Si MAS solid-state NMR confirm that the aspartic acid is incorporated into the framework of the PMOs materials.

Poor dispersity and low stability are two predominant shortcomings hindering the applications of metal–organic polyhedra (MOPs). The confinement of MOPs in nanoscale cavities of mesoporous matrices is efficient in overcoming both shortcomings, while the improvement of the current double-solvent method is highly expected. Here we develop a facile, controllable strategy to fabricate three MOPs (coordinated from dicopper and carboxylates) in confined cavities via in situ site-induced assembly (SIA), for the first time. The cavities of mesoporous matrix SBA-16 were pre-functionalized with amine sites, which induce in situ assembly of precursors that diffused into cavities. Hence, both the amount and location of MOPs in the mesoporous matrix can be easily controlled. Upon confinement, the dispersity, stability, and catalytic performance (on ring-opening reactions) of MOPs are greatly improved. Moreover, the enhancement of stability makes it possible to observe MOPs using high-resolution transmission electron microscopy (HRTEM) directly.

Adsorption and desorption are equally important in an adsorptive separation process, while conventional adsorbents with fixed pores benefit only one of them rather than both. Here, a new generation of adsorbents was fabricated by incorporating thermo-responsive polymers (TRPs) into pores. The TRPs act as molecular switches, making pore spaces and active sites responsive to adsorption/desorption conditions. The adsorbents can thus realize both selective adsorption and efficient desorption, which are extremely desirable for adsorptive separation.

New solid strong bases were fabricated at room temperature by grafting lithium-containing molecular precursors onto β-cyclodextrin. The solid bases show strong basicity with a molecular-level dispersion of lithium sites, which are highly active in transesterification reactions and impossible to realize through the traditional high-temperature method.

Template-derived carbon is demonstrated to effectively promote the creation of strong basicity on mesoporous silica, for the first time. New materials owning ordered mesoporous structure, strong basicity, and excellent catalytic activity are thus successfully constructed at low temperatures, which are impossible to achieve using conventional methods.

A new generation of smart adsorbents was designed by grafting photo-responsive molecules onto the pore entrances of mesoporous silica. These molecules act as the gates of the mesopores, which are reversibly closed/opened upon light irradiation. Our smart adsorbents thus realize both selective adsorption and efficient desorption, which is highly expected for adsorption but impossible for traditional adsorbents with fixed pore entrances.

A redox strategy was designed to generate strong basicity on mesoporous silica by using the redox interaction of a precursor with methanol vapor. The formation of strongly basic sites was realized at 400 °C, which breaks the tradition of thermally induced decomposition that usually requires much higher temperatures (>600 °C).

Due to their versatility, nontoxicity, and low cost, Cu(I) ion exchanged zeolites are of great interest for various applications. Despite many attempts, the development of an efficient, controllable, and energy-saving approach to fabricate Cu(I) sites in zeolites remains an open question. In this study, a strategy was developed to convert Cu(II) in zeolites to Cu(I) selectively using vapor-induced reduction (VIR) with methanol. The methanol vapors generated at elevated temperatures diffuse into the pores of zeolites and interact with Cu(II) ions, leading to the formation of Cu(I). This strategy allows the construction of Cu(I) sites at low temperatures and avoids the formation of Cu(0). Moreover, the obtained material exhibits excellent performance in the adsorptive separation of propylene/propane with regard to both capacity and selectivity, which is obviously superior to the material prepared by the conventional autoreduction method as well as using various typical adsorbents.

Metal–organic frameworks (MOFs) have attracted extensive attention due to their large surface area, diverse structures, and tuneable functionality. However, the poor hydrostability of most reported MOFs hinders their practical applications severely. In this paper, we report a strategy to modulate the properties of a typical MOF, namely MOF-5 [Zn4O(BDC)3; BDC = 1,4-benzenedicarboxylate] by hybridizing it with a natural clay (i.e. attapulgite), for the first time. A new kind of hybrid material resulting from the hybridization of the MOF and attapulgite was thus constructed. Our results showed that the hydrostability of the MOF was apparently improved due to the hybridization with attapulgite. The frameworks of MOF-5 were degraded seriously under the humid atmosphere, while the structure of the hybrid materials could be well preserved. We also demonstrated that the hybrid materials were highly active in the heterogeneous Friedel–Crafts alkylation reaction of benzyl bromide with toluene. The conversion of benzyl bromide reached ∼100% under the reaction conditions investigated. More importantly, the catalytic stability of the hybrid materials was significantly enhanced owing to the introduction of attapulgite. The activity could be well recovered with no detectable loss, and the conversion remained at ∼100% at the sixth run, which was apparently higher than that of MOF-5 (27.7% at the sixth run). The excellent hydrostability, catalytic activity, and reusability make the present materials highly promising for utilization as heterogeneous catalysts in practical applications.

Deep desulfurization of transportation fuels via π-complexation adsorption is an effective method for the selective capture of aromatic sulfur compounds. Taking into consideration that the desulfurization of transportation fuels proceeds in the liquid phase, separation and recycling of adsorbents should be greatly facilitated if the adsorbents were endowed with magnetism. In this paper, magnetically responsive core–shell π-complexation adsorbent microspheres, AgNO3/Fe3O4@mSiO2 (mSiO2 denotes mesoporous silica), which comprises a core of magnetite particles and a shell of mesoporous silica dispersed with AgNO3, was developed for the first time. The silica shell exhibits highly open mesopores with perpendicularly aligned pore channels, large surface area (694 m2 g−1) and uniform pore size (2.3 nm), which is quite beneficial to the accommodation of Ag(I) active species. As a result, AgNO3 can be well dispersed in the pores of silica shells and are highly accessible to adsorbate molecules. Our results show that the adsorbent is active in the adsorptive removal of a typical aromatic sulfur compound, thiophene, via π-complexation under ambient conditions. More importantly, the superparamagnetism allows the adsorbent to be separated conveniently from the adsorption system in several seconds by the use of an external field. After desulfurization, the adsorbents were regenerated by washing with isooctane and subsequent thermal dispersion in Ar. The regenerated adsorbent after six cycles still shows a good adsorption capacity (0.145 mmol g−1 or 4.64 mg g−1), which is comparable to the fresh adsorbent (0.147 mmol g−1 or 4.70 mg g−1). The magnetically responsive π-complexation adsorbent may be a promising candidate for the deep purification of transportation fuels.

Due to their synthetic diversification, low skeletal density, and high physicochemical stability, porous polymer networks (PPNs) are highly promising in a variety of applications such as carbon capture. Nevertheless, complicated monomers and/or expensive catalysts are normally utilized for their synthesis, which makes the process tedious, costly, and hard to scale up. In this study, a facile nucleophilic substitution reaction was designed to fabricate PPNs from low-cost monomers, namely chloromethyl benzene and ethylene diamine. A surfactant template was also used to direct the assembly, leading to the formation of PPN with enhanced porosity. It is fascinating that the polymerization reactions can occur at the low temperature of 63 °C in the absence of any catalyst. The obtained PPNs contain abundant secondary amines, which offer appropriate adsorbate–adsorbent interactions from the viewpoints of selective CO2 capture and energy-efficient regeneration of the adsorbents. Hence, these PPNs are highly active in selective adsorption of CO2, and unusually high CO2/N2 and CO2/CH4 selectivity was obtained. Moreover, the PPN adsorbents can be completely regenerated under mild conditions.

Because of the high stability, tailorable surface properties, and plentiful porosity, nitrogen-doped porous carbons (NPCs) are of great interest for CO2 capture. Carbonization of nitrogen-containing polymers is regularly utilized for the fabrication of NPCs, but such a method is obstructed by the high cost of some polymer precursors. Here we demonstrate the preparation of NPCs via the rational choice of a low-priced, nitrogen-rich polymer NUT-1 (NUT represents Nanjing Tech University) as the precursor, for the first time. The polymer NUT-1 was synthesized by the polymerization of two easily available monomers under mild conditions without the use of any catalysts. Carbonization at temperatures ranging from 500 to 800 °C leads to the generation of a series of NPCs possessing various porosity and nitrogen contents. The adsorption performance of NPCs is dependent on their pore structure and nitrogen-doped “CO2-philic” sites, while the sample with the largest surface area does not exhibit the highest adsorption amount of CO2. In the case of the material prepared at 600 °C (NPC-1-600), the CO2 adsorption amount can reach 7.5 mmol g−1 at 273 K and 1 bar, which is much higher than that of some benchmark materials, including 13X zeolite (4.1 mmol g−1) and activated carbon (2.8 mmol g−1), and most if not all reported carbon-based adsorbents. We also demonstrate that KOH plays an important role in the formation of abundant porosity. The reference material NPC-1-600r prepared in the absence of KOH can only adsorb 3.2 mmol CO2 g−1 at 273 K and 1 bar, which is obviously lower than its counterpart NPC-1-600 (7.5 mmol g−1). Our materials may offer to be promising candidates for carbon capture from gas mixtures including natural gas and flue gas.

Mesoporous solid bases are extremely desirable in green catalytic processes, due to their advantages of accelerated mass transport, negligible corrosion, and easy separation. Great progress has been made in mesoporous solid bases in the last decade. In addition to their wide applications in the catalytic synthesis of organics and fine chemicals, mesoporous solid bases have also been used in the field of energy and environmental catalysis. Development of mesoporous solid bases is therefore of significant importance from both academic and practical points of view. In this review, we provide an overview of the recent advances in mesoporous solid bases, which is basically grouped by the support type and each category is illustrated with typical examples. Cooperative catalysts derived from the incorporation of additional functionalities (i.e. acid and metal) into mesoporous solid bases are also included. The fundamental principles of how to design and fabricate basic materials with mesostructure are highlighted. The mechanism of the formation of basic sites in different mesoporous systems is discussed as well.