•Two novel nickel quinolinethiolate complexes based photocatalysts (1, 2) is reported.•H2 evolution activity of 1, 2 reached 5923/7634 TON in the noble-metal-free system.•A H2 evolution mechanism of heterocoupling between NiH− and NH+ is proposed.•The elaborate nickel photocatalysts are efficient and stable.Earth-abundant metal complexes have emerged as promising surrogates of platinum for catalyzing the hydrogen evolution reaction (HER). In this study, we report the design and synthesis of two novel nickel quinolinethiolate complexes, namely [Ni(Hqt)2(4, 4′-Z-2, 2′-bpy)] (Hqt = 8-quinolinethiol, Z = H [1] or CH3 [2], bpy = bipyridine). An efficient three-component photocatalytic homogeneous system for hydrogen generation working under visible light irradiation was constructed by using the target complexes as catalysts, triethylamine (TEA) as sacrificial electron donor and xanthene dyes as photosensitizer. We obtain turnover numbers (TON, vs. catalyst) for H2 evolution of 5923/7634 under the optimal conditions with 5.0 × 10−6 M complex 1/2 respectively, 1.0 × 10−3 M fluorescein and 5% (v/v) TEA at pH 12.3 in EtOH/H2O (1:1, v/v) mixture after 8 h irradiation (λ > 420 nm). We discuss the mechanism of H2 evolution in the homogeneous photocatalytic system based on fluorescence spectrum and cyclic voltammetry data.The novel nickel quinolinethiolate complexes displayed efficient hydrogen evolution in a noble-metal-free photocatalytic system under visible light.

•Four new bionic photocatalysts (1–4) with [2Fe2S] model complexes were reported.•H2 evolution of 1–4 was evaluated, the max H2 yield reached 52.9 ± 1.6 TON (vs. 4).•Inactivity of system was mainly due to photo-degradation of EBS2− and catalyst (1–4).•Reduced FeIFe0 species could be formed by ET from 1*EBS2− to FeIFeI.•The effect of [2Fe2S] complexes’ structure on H2 production mechanism was discussed.Four novel [2Fe2S] model complexes (1–4) had been synthesized and characterized by IR, 1H NMR, elemental analysis and single crystal X-ray crystallography (for 2). The key parameters affecting H2 evolution of title compounds (1–4) were optimized by constructing homogeneous photo-catalytic system consisting of title compounds (1–4) as catalyst, erythrosin B sodium salt (EBS2−) as photo-sensitizer (PS) and triethylamine (TEA) as sacrificial reagent in CH3CN/H2O solution under the irradiation of visible light. The maximum H2 evolution was separately 211.4 ± 6.5 μmol (52.9 ± 1.6 TON vs. 4), 199.4 ± 13.5 μmol (49.9 ± 3.4 TON vs. 1), 124.8 ± 7.6 μmol (31.2 ± 1.9 TON vs. 3) and 34.9 ± 6.9 μmol (8.7 ± 1.7 TON vs. 2) under the optimal conditions with catalyst of 2 × 10−4 mol·L−1, EBS2− of 4 × 10−4 mol·L−1, TEA of 10% (v/v) and pH 12 in CH3CN/H2O (1/1, v/v) solution. Furthermore, the structural effect and mechanism of electron transfer in the present system was carefully discussed by fluorescence spectra and cyclic voltammetry (CV) measurements.We have constructed a homogeneous photo-catalytic system using [2Fe2S] model complexes 1–4 as biomimetic photo-catalysts, EBS2− as PS and TEA as sacrificial reagent in CH3CN/H2O (v/v, 1/1) solution under the visible light irradiation. The H2 evolution performance and mechanism of target complexes 1–4 were evaluated. The result suggested that the different structures of [2Fe2S] simulate complexes affect on H2 evolution performance and mechanism, the maximum H2 evolution was 211.4 ± 6.5 μmol (52.9 ± 1.6 TON vs. 4). The H2 generation mechanism might be able to firstly form an intermediate Fe0FeI by electron transferring from 1*EBS2− to [2Fe2S] center, and then underwent an ECEC (for 1, 2 and 4) or EECC (for 3) process to form the important H2–Fe2S2 (η2-H2–FeIIFeI) species of H2 production. The result indicated the target complexes are potential candidates as photo-catalysts for H2 generation.

Statistical analyses had been used to optimize the process parameters of H2 production from untreated raw corn stalk by Clostridium sp. FZ11. Five variables, including the temperature, initial pH, urea, phosphate-buffered saline (PBS), and nutrient solution, had been screened through the Plackett–Burman design. Experimental results indicated that urea, PBS, and nutrient solution were the most important variables, which were further optimized using the steepest ascent method and Box–Behnken design. The maximum H2 yield of 96.2 mL/g from untreated raw corn stalk was recorded under the optimal conditions of 6.21 g/L urea, 0.19 M PBS, and 8.74 mL/L of nutrient solution. Meanwhile, about 45% of cellulose and 53% of hemicellulose were biodegraded by H2 fermentation.

Two novel metal dithiolene complexes, namely NtBu4[M(BNT)2] [M = Co/Ni, (BNT = (R)-1, 1′-binaphthalene-2,2′-dithiol)], have been synthesized and characterized. An efficient homogeneous photocatalytic system was constructed by a combination of the noble-metal-free target complexes as water reduction catalysts, xanthene dyes as the photosensitizer and triethylamine (TEA) as the sacrificial electron donor under irradiation with visible light (λ > 420 nm). Maximum H2 evolution of 495 and 676 turnovers (vs. catalyst) were recorded for each catalyst, respectively, under optimal conditions in CH3CN/H2O (1:1, v/v) after 4 h of irradiation. Furthermore, the mechanism of the H2 evolution was also briefly discussed alongside fluorescence spectra and cyclic voltammetry studies.

The enhanced H2 production from maize straw had been achieved through the two-stage process of integrating H2 fermentation and microbial electrolysis cells (MECs) in the present work. Several key parameters affecting hydrolysis of maize straw through subcritical H2O were optimized by orthogonal design for saccharification of maize straw followed by H2 production through H2 fermentation. The maximum reducing sugar (RS) content of maize straw reached 469.7 mg/g-TS under the optimal hydrolysis condition with subcritical H2O combining with dilute HCl of 0.3 % at 230 °C. The maximum H2 yield, H2 production rate, and H2 content was 115.1 mL/g-TVS, 2.6 mL/g-TVS/h, and 48.9 % by H2 fermentation, respectively. In addition, the effluent from H2 fermentation was used as feedstock of MECs for additional H2 production. The maximum H2 yield of 1060 mL/g-COD appeared at an applied voltage of 0.8 V, and total COD removal reached about 35 %. The overall H2 yield from maize straw reached 318.5 mL/g-TVS through two-stage processes. The structural characterization of maize straw was also carefully investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) spectra.

•A binuclear complex [Co2(dmgH)4(μ-4,4′-bpy)Cl2](1) was synthesized and characterized.•Electrochemical property and photocatalytic H2 evolution of 1 was evaluated.•Photolysis system composed of 1 of 3.7 × 10−4 M, EY2− of 4 × 10−4 M and TEOA of 20 vol%.•The maximum H2 yield of 1479.9 μmol was recorded at pH10 in irradiation 2 h.•The electron transfer from 1*EY2− to 1 was confirmed to be thermodynamically feasible.A new binuclear cobalt complex, namely [Co2(dmgH)4(μ-4,4′-bpy)Cl2](1), had been synthesized by the reaction of [Co(dmgH)(dmgH2)Cl2] with 4,4′-bipyridine(μ-4,4′-bpy) and characterized by IR, 1H NMR, CV. An efficient homogeneous photocatalytic system was constructed by combination of noble-metal-free cobalt complex as catalyst, Eosin Y dye (EY2−) as photosensitizer and TEOA as sacrificial reagent under visible-light irradiation (λ > 420 nm). The maximum H2 yield of 1488.3 ± 34.5 μmol (160.0 ± 3.7 TON vs. 1) and H2 evolution rate of 744.2 ± 17.3 μmol h−1 were recorded under the optimal conditions with 1 of 3.7 × 10−4 mol L−1, EY2− of 4 × 10−4mol L−1, TEOA of 20% (v/v) and pH 10 in 2 h irradiation. Furthermore, the mechanism of H2 evolution in the homogeneous photolysis system was also briefly discussed. The electron transfer from the excited 1*EY2− to Co catalytic center of complex 1 in the designed system was also confirmed to be thermodynamically feasible.Graphical abstract

•Bio-H2 yield from corn stalk was enhanced by integrating dark fermentation and MECs.•Max. H2 yield of 387.1 mL/g-corn stalk was recorded by two-stage process.•H2 recovery and production rate reached 257.3 ml/g-straw and 3.43 ± 0.12 m3/m3 d in MECs.•Energy efficiency and effluent COD removal reached 166 ± 10% and 44 ± 2% in MECs.•MECs played a critical role in generating additional H2 and effluent COD removal.The low conversion efficiency of substrate is one of the main bottlenecks in dark fermentation for bio-H2 production. Herein, an enhanced H2 yield from corn stalk was achieved by integrating dark fermentation and single chamber microbial electrolysis cells (MECs). In the dark fermentation stage, a H2 yield of 129.8 mL H2/g-corn stalk and an average H2 production rate of 1.73 m3/m3 d were recorded at 20 g/L of corn stalk and initial pH 7.0. The effluent from dark fermentation was diluted and further employed as feedstock to generate H2 by MECs. A H2 yield of 257.3 mL H2/g-corn stalk, an HPR of 3.43 ± 0.12 m3/m3 d and an energy efficiency of 166 ± 10% were obtained with the effluent COD of 3995.5 mg/L under 0.8 V applied voltage. During MECs operation stage, about 90 ± 2% of acetate was converted to H2 and the corresponding COD removal reached 44 ± 2% in MECs. Overall, the H2 yield can reach 387.1 mL H2/g-corn stalk by integrating dark fermentation and MECs, which had nearly tripled as against that of dark fermentation.

•Higher concentration of maize-straw (60 g/L) was used as feedstock for H2 production.•Maximal H2 yield 79.8 ± 1.5 ml/g-TS and H2 production rate 3.78 ml/g-TS h was found.•Effluent from H2 fermentation was used to produce CH4 by anaerobic digestion.•Maximum CH4 yield of 227 ± 2.5 ml/g-COD and COD removal rate of 96% was recorded.•Co-producing H2 and CH4 from corn stalk by two-step fermentation was feasible.In this paper, the high concentration of corn stalk (60 g/L) was employed as feedstock to produce bio-hydrogen and methane by combining hydrogen fermentation and anaerobic digestion. In the first stage of hydrogen fermentation, the effects of several key parameters, such as strain enhancement technique, cetyl trimethyl ammonium bromide (CTAB), NH4HCO3 on hydrogen production from cornstalk were investigated and optimized. The maximum hydrogen yield of 79.8 ± 1.5 ml H2/g-TS and hydrogen production rate of 3.78 ml/g-cornstalk h was observed at fixed acidizing cornstalk of 60 g/L, strains Bacillus sp. FS2011 dosage of 10%(v/v), CTAB of 30 mg/L, NH4HCO3 of 1.2 g/L and initial pH of 7.5 ± 0.5 at 36 ± 1 °C, respectively. In the second stage of anaerobic digestion, the effluent from hydrogen production bio-reactor was further employed as the feedstock to produce methane by methanogenic bacteria, the maximum methane yield of 227 ± 2.5 ml CH4/g-COD and COD removal rate of 95  ± 1% was recorded. The interesting observations were that the total amount of the organic wastewater produced in a higher substrate concentration (60 g/l) by hydrogen fermentation was reduced by about two-thirds compared with that of traditional low substrate concentration (≤20 g/l).

Two new binuclear cobalt complexes, namely {[Co(dmgH)(dmgH2)]2L1} (I) and {[Co(dmgH)(dmgH2)]2L2} (II) (dmgH = dimethylglyoximate monoanion; dmgH2 = dimethylglyoxime, L1 = 1,3-bis(4-pyridyl)propane), L2 = 1,3-bis(imidazol-1-ylmethyl)benzene), have been synthesized by the self-assembly of [Co(dmgH)(dmgH2)] and L1 or L2, respectively. An efficient photocatalytic system was constructed by combining a noble-metal-free cobalt complex as the catalyst with Eosin Y dye (EY2−) as the photosensitizer to give an efficient H2 generating system under visible-light irradiation (λ > 420 nm) using triethanolamine (TEOA) as a sacrificial electron donor. The maximum amount of H2 generated was 1013 TON for I and 1134 TON for II over a 2 h irradiation period (λ > 420 nm) under the conditions of pH 8.0, 5% TEOA (v/v), an EY2− concentration of 4.0 × 10−4 M and a catalyst concentration of 4.0 × 10−4 M in the mixed solvent system of CH3CN–H2O (3:1, v/v). In addition, the mechanism of H2 generation in the photolysis system was briefly discussed.

•A novel complex [RuL(bpy)2](PF6)2 (TM1) was synthesized.•TM1 was characterized by UV–vis, IR, NMR MS and CV.•Target photocatalyst Ⅰ was operated and characterized by SEM and EDS.•The maximum H2 yield of 386.7 μmol in irradiation 3 h was detected.•The optimal H2 condition was pH 5, photo-catalyst Ⅰ of 50 mg and 5 vol% TEOA.A new organic–inorganic photosensitive coordination compound [RuL(bpy)2](PF6)2 (to represent by TM1) had been synthesized by reaction of L (L = 2-hydroxyl-5-(imidazo-[4,5-f]-1,10-phenanthrolin) benzoic acid) with bipyridyl ruthenium, and further characterized by UV–vis, IR, NMR MS and CV. The target photocatalyst 6 wt% TM1-0.5 wt% Pt-TiO2 (Ⅰ) was obtained by sensitization of Pt-loaded TiO2 with TM1. The H2 production activity of target photocatalyst Ⅰ was systematically evaluated by the reaction of photocatalytic H2 production from water under visible light irradiation. The maximum H2 evolution of 386.7 μmol in irradiation 3 h and H2 production rate of 2578 μmol · h−1 · g−1 was detected under the optimal conditions with pH 5, target photocatalyst Ⅰ 50 mg and 5% sacrificial reagent TEOA (v/v).

Hydrothermal reactions of Mn(II), Co(II), Cu(II), and Cd(II) salts with 2-((1H-1,2,4-triazol-1-yl)methyl)-1H-imidazole-4,5-dicarboxylic acid (H3tmidc) lead to four novel coordination polymers, namely, [Mn3(tmidc)2(H2O)4]·(H2O)6 (1), [Co3(tmidc)2(H2O)4]·(H2O)4 (2), [Cu3(tmidc)2(H2O)]·(H2O) (3), and [Cd(Htmidc)] (4). Compound 1 has a three-dimensional (3D) architecture, and the topological study shows that its framework features a 3D (3,4)-connected fsc-3,4-Pbca network with the Schläfli topological symbol of (63)(63.83). Compound 2 exhibits a 3D pillared framework constructed by 4-fold one-dimensional (1D) helical chains and possesses open helical channels in the framework. Topological analysis reveals that it is a unique (3,4)-connected net with the Schläfli symbol of (4.52)(4.5.114) which is not enumerated in RCSR andTOPOS, and has not been reported in the literature. Compound 3 features a 3D intricate framework displaying a new (3,4)-connected 4-nodal net with the Schläfli symbol of (5.72)(4.5.7)(52.72.8.10)(4.5.73.8) which has not been observed in any other coordination polymers. Topological analysis of the 3D network found in compound 4 reveals that the whole structure can be rationalized as a (4.65)(4.65) crb topological net.

A novel cadmium coordination polymer, [Cd(tmb)(Cl)(CH3OH)]n (1) (Htmb = 2-(1H-triazol-1-ylmethyl)-1H-benzoimidazole), has been solvothermally synthesized and structurally characterized by IR, elemental analysis, thermogravimetric analysis and single-crystal X-ray diffraction. 1 crystallizes in the trigonal system, R, with a = 22.496(3), b = 22.496(3), c = 14.870(3) Å, V = 6516.7(19) Å3 and Z = 18. Interestingly, 1 possesses a unique three-dimensional framework, based on the dodecanuclear Cd(II) macrocycles, and contains two different types of pseudo-helical chain with left- and right-handed characters, which present alternately along the metallamacrocycle. In addition, 1 exhibits an enhanced fluorescent intensity at 77 K in comparison to its emission at room temperature.

Effects of pretreatment of natural bacterial source and raw material on biohydrogen production in fermentative biohydrogen production process were investigated systematically. Biohydrogen production from stale corn slurry was found to be feasible and effective by A1 (water soak) pretreated compost and B1 (gelatinization) pretreated stale corn. The results were further confirmed by the verification test with working volume of 8 L, in which the maximum hydrogen yield of 262 mL H2/g-substrate, hydrogen production rate of 39 mL/g h−1 and the corresponding hydrogen content of 50% was observed at fixed substrate concentration of 10 g/L, working pH 5.0–5.5 and 36 ± 1 °C. The effluent was mostly composed of acetate and butyrate. Subsequently, two new hydrogen producing strains were isolated from the effluent sludge in the running bioreactor, and they were preliminarily identified as Clostridium and Enterobacter, respectively, according to the routine screening examinations.Highlights► Different pretreatment methods of manure compost and stale corn were investigated. ► Integration of soaked compost with gelatinization of stale corn was most effective. ► The maximum H2 yield of 262 mL H2/g appeared at 10 g/L-substrate, pH 5.0–5.5 and 36°C. ► H2 producing strains were isolated from the liquid effluent of the bioreactor. ► Two screened strains were identified as Clostridium and Enterobacter, respectively.

The effects of pretreatment method of cow dung compost, which was employed as natural hydrogen bacteria source, on the microbial community, population distribution of microbes and hydrogen production potential were investigated in the batch tests. The maximum hydrogen yield of 290.8 mL/L-culture appeared in the pretreated method A (infrared drying) by dark fermentation. The pretreated method of compost significantly affected microbial succession, population distribution of microbes. Both Clostridium sp. and Enterobacter sp. were found to be two species of preponderant hydrogen-producing bacteria, the next best was Bacteroides sp. and Veillonella sp., the last was Lactobacillus sp. and Streptococcus sp., which were also essential. The results showed that the mutualism and symbiosis relations of the mixed bacteria played a critical role in hydrogen fermentation process.Highlights► The pretreatment of compost vitally affected microbial succession in mixed culture. ► The max H2 yield of 290.8 ml/L-culture occurred in compost of infrared drying. ► Both Clostridium sp. and Enterobacter sp. were two preponderant H2-producing bacteria. ► The synergistic action of the mixed bacteria was found in the batch test.

The bio-hydrogen production potential from corn stalk was significantly affected by microwave irradiation pretreatment of cow dung compost in batch tests. The maximum hydrogen yield of 144.3 ml/g-corn stalk and hydrogen production rate of 3.6 ml/g-corn stalk h−1 were observed using the pretreated compost by microwave radiation of 1.5 min at fixed Na2CO3 dosage of 800 mg/l, Fe dosage of 400 mg/l, substrate concentration of 20 g/l, which increased about 99.6% and 85.2% compared with that of the control. The effects of microwave irradiation on microbial characteristics were further discussed by Atomic Force Microscope (AFM), determination of protein content and PCR-DGGE. The four dominant hydrogen-producing strains had been isolated and confirmed to be Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus subtilis and Enterococcus faecium, respectively. The diversity and symbiosis relations of the mixed bacteria were also observed in fermentation hydrogen production process.Highlights► The microwave irradiation of compost was an effective strategy for raising bio-H2 yield. ► The high H2 yield of 144.3 ml/g-corn stalk and R of 3.6 ml/g h−1 occurred in the batch test. ► The addition level of Fe and Na2CO3 also effected remarkably the H2 yield of substrate. ► The mechanism on microwave irradiation of compost was studied by AFM and PCR-DGGE.

An uncommon butterfly-like tetranuclear copper(II) cluster with the formula {[Cu4(μ3-OH)2(μ4-Cl)(H2O)2(L)2]·Cl(H2O)7}n (1) (H2L = 1,2-bis[3-(1,2,4-triazolyl)-4-amino-5-carboxylmethylthio]ethane) has been synthesized. Compound 1 exhibits interesting anion exchange characteristics, in which both guest and coordinated Cl− can be replaced by I− or NO3− in water. Furthermore, a high catalytic selectivity to produce poly(phenylene ether) by the oxidative coupling of 2,6-dimethylphenol in water is found to be 74% for 1 and 87% for the anion-exchanged product 1-MIx, respectively. Additionally, the antiferromagnetic interaction among Cu ions for compound 1 is also found.

The cellulosic hydrogen production from cornstalk based on the integrating dilute acid with enzymatic hydrolysis was investigated using response surface methodology (RSM). The dilute acid pretreatment of cornstalk with the concentration of 1.5% H2SO4, 121 °C and 60 min was found to be most effective in the first prehydrolysis stage. Thereafter, the process parameters of enzymatic hydrolysis of the solid residue, which derived from acid-pretreated cornstalk, were further optimized by a three factor-five level central composite design (CCD) with temperature (X1), pH (X2), and enzyme loading (X3) as the independent variables. The optimal parameters of enzymatic hydrolysis of substrate were observed to be 52 °C of temperature, pH 4.8 and 9.4 IU/g of enzyme loading. In this case, the total soluble sugar obtained in the hydrolysis stages was 562.1 ± 6.9 mg/g-TVS, and the maximum hydrogen yield from cornstalk by anaerobic mixed microflora was 209.8 ml/g-TVS. Biodegradation mechanism of cornstalk for hydrogen production was further discussed based on analyzing changes in the physical structure and chemical composition of cornstalk during the hydrolysis and fermentation processes.

A hydrogen producing strain F.P 01 was newly isolated from cow dung sludge in an anaerobic bioreactor. The strain F.P 01 was a mesophilic and facultative anaerobic bacterium, which exhibited gram-negative staining in both the exponential and stationary growth phases, and a regular long rod-shaped bacteria with the size of 0.6–0.9 μm × 1.2–2.5 μm, and also could biodegrade a variety of carbohydrates such as glucose, xylose, maltose, etc. The effects of important process parameters on hydrogen producing of F.P 01 were further investigated from hydrogen fermentation of maltose by strain F.P 01, including substrate concentration, medium pH, etc. And the results showed that hydrogen production potential and hydrogen production rate from maltose of this strain F.P 01 was180 mLH2/g-maltose and 4.0 mLH2/h, respectively. The corresponding hydrogen concentration of 58–73% was also be observed. Both butyric acid and acetic acid as main by-product was left in the reactor.

Strategies were adopted to cost-efficiently produce cellulose-hydrogen by anaerobic fermentation in this paper. First, cellulase used for hydrolyzing cellulose was prepared by solid-state fermentation (SSF) on cheap biomass from Trichoderma viride. Several cultural conditions for cellulase production on cheap biomass such as moisture content, inoculum size and culture time were studied. And the components of solid-state medium were optimized using statistical methods to further improve cellulase capability. Second, the crude cellulase was applied to cellulose-hydrogen process directly. The maximal hydrogen yield of 122 ml/g-TVS was obtained at the substrate concentration of 20 g/L and cultured time of 53 h. The value was about 45-fold than that of raw corn stalk wastes. The hydrogen content in the biogas was 44–57%(v/v) and there was no significant methane gas observed.

Four novel lanthanide(III) coordination polymers [Ln(L)1.5(H2O)2]·5H2O [Ln = Sm (1), Eu (2), Tb (3), Dy (4)] have been hydrothermally synthesized by the reaction of 1,2-bis[4-amino-5-carboxylmethylthio-(1,2,4-triazol-3-yl)]ethane (H2L) with lanthanide(III) salts, and structurally characterized by single crystal X-ray diffraction. Polymers 1–4 are isostructural, in which all the LnIII atoms are nine-coordinated and the carboxylate groups adopt three different coordination modes (bidentate chelate, bidentate bridging, bidentate chelate bridging) to connect LnIII atoms. These polymers exhibit 3D network structures with 2-fold interpenetration, in which intriguing 1D channels are observed. Besides, the spectra properties of the title polymers are investigated, the strong luminescence characteristics of 2–3 are found.Four novel lanthanide(III) coordination polymers [Ln(L)1.5(H2O)2]·5H2O [Ln = Sm (1), Eu (2), Tb (3), Dy (4)] have been hydrothermally synthesized by the reaction of 1,2-bis[4-amino-5-carboxylmethylthio-(1,2,4-triazol-3-yl)]ethane (H2L) with lanthanide(III) salts. These polymers exhibit 3D network structures with 2-fold interpenetration, in which intriguing 1D channels are observed.

Two novel inorganic–organic 3D network, namely{[Ln(L)1.5(H2O)2]·5H2O}n [Ln=Y (1), Ce (2)] [Ln(L)1.5(H2O)2]·5H2O [Ln=Y (1), Ce (2)], have been prepared through the assembly of the ligand 1,2-bis[3-(1,2,4-triazolyl)-4-amino-5-carboxylmethylthio]ethane (H2L) and lanthanide (III) salts under hydrothermal condition and structurally characterized by single-crystal X-ray diffractions. In complexes 1 and 2, the L2− anions adopt three different coordination fashions (bidentate chelate, bidentate bridging and bidentate chelate bridging) connecting Ln(III) ions via the oxygen atoms from carboxylate moieties. Both 1 and 2 exhibit 3D network structures with 2-fold interpenetration. Interestingly, the reversible desorption–adsorption behavior of lattice water is significantly observed in the two compounds. The result shows their potential application as late-model water absorbent in the field of adsorption material.Two inorganic–organic 3D network, namely {[Ln(L)1.5(H2O)2]·5H2O}n [Ln=Y (1), Ce (2)], have been prepared under hydrothermal condition and structurally characterized by single-crystal X-ray diffractions. Both 1 and 2 exhibit 3D network structures with 2-fold interpenetration. Interestingly, the reversible desorption–adsorption behavior of lattice water is significantly observed in the two compounds. The result shows their potential application as late-model water absorbent in the field of adsorption material.

Hydrothermal reactions of Mn(II), Cu(II), Co(II), and Ni(II) salts with 2-(1-triazole)-1-hydroxyl-1,1′-ethylidenediphosphonic acid (tahedpH4) lead to four novel metal phosphonates, namely, Mn2(tahedp)(H2O)2 (1), Cu2(tahedp)(H2O) (2), Co(tahedpH2) (3) and Ni2(tahedpH2)2·(NH2CH2CH2NH2) (4). In compound 1, dimeric units {Mn12O2} are linked together by the O3−P1−O1 groups forming an inorganic chain. The adjacent chains are further connected by {Mn2O4N} pentahedra to form an undulating inorganic layer. The inorganic layers are bridged by the triazole groups resulting in a three-dimensional framework structure. In the opinion of the topology, the structure of 1 can be described as an unprecedented trinodal (4.66.83)2(42.62.82)(5.62)2 topological network. Compound 2 shows a pillared layered structure in which the {Cu12O2} dimers are linked together by the O3−P1−O1 groups forming a double chain. The double chains and the {−Cu2−O5−P2−O4−}2 eight-membered rings are further linked through the coordination of O2 and O6 atoms into a layer. The neighboring layers are connected together by the triazole rings, resulting in a pillared layered structure. Topological analysis of compound 2 reveals that it is a unique 3, 4, and 5-connected net with (42.6)2(42.84)(43.6.86)2 topology. Compound 3 exhibits a layer structure made up of Co2(tahedpH2)2 dimer units. Compound 4 exhibits a layer architecture that built from {NiO5N} octahedra interconnected by phosphonate groups and triazole rings. Magnetic measurements reveal that antiferromagnetic interactions are mediated between magnetic centers in all four compounds.

Biohydrogen production by anaerobic culture using aging corn as the feedstock is reported for the first time. The biopretreatment of aging corn with solid microbe additives was essential for adequate conversion of the substrate into biohydrogen. The maximum H2 yield (Ps) and H2 production rate (R) utilizing aging corn were 346 (mL of H2)/(g of TVS) and 11.8 mL/h, respectively, at a fixed substrate concentration of 10 g/L and an initial pH of 6.0 by dairy manure compost in a batch validation test. The H2 yield was approximately 2.5 times that obtained from raw aging corn. During the optimal hydrogen-producing period, the oxidation−reduction potential ranged from −521 to −458 mV. Both butyrate (49.4−55.7%) and acetate (23.7−28.5%) as the two main byproducts were left in the reactor in the process of hydrogen fermentation during the conversion of aging corn into hydrogen.

Three new d10 coordination polymers, namely [Cd(taa)Cl]n1, [Hg(taa)Cl]n2, and [Ag1.5(taa)(NO3)0.5]n3 (taa=1H-1,2,4-triazole-1-acatate anion) have been prepared and characterized by elemental analysis, IR, and single crystal X-ray diffraction. Compound 1 consists of two-dimensional layers constructed by carboxyl-linked helical chains, which are further linked through carboxyl group to generate a unique 3D open framework. Topological analysis reveals that the structure of 1 can be classified as an unprecedented (3,8)-connected network with the Schläfli symbol (4.52)2(42.58.614.73.8). Compound 2 manifests a doubly interpenetrated decorated α-polonium cubic network with the Schläfli symbol of (410.62.83). Compound 3 consists of 2D puckered layers made up of Ag centers and taa− bridges. In addition, all of these compounds are photoluminescent in the solid state with spectra that closely resemble those of the ligand precursor.Three new compounds based on 1H-1,2,4-triazole-1-acetic acid and Cd(II), Hg(II) and Ag(I) salts display luminescent properties and may be potential candidates for luminescent materials.

Five new transition metal coordination polymers based on H2tzda and co-ligand bpe, {[M(tzda)(bpe)]·H2O}n [M=Zn(1), Cd(2), Mn(3), Co(4)] and [Ni2(tzda)2(bpe)2(H2O)]n (5) [H2tzda=(1,3,4-thiadiazole-2,5-diyldithio)diacetic acid, bpe=1,2-bis(4-pyridyl)ethane], have been hydrothermally synthesized and structurally characterized. Compounds 1–4 feature a 2D-layered architecture generated from [M(tzda)]n moiety with double-chain structure cross-linking bpe spacers. However, the conformations bpe adopts in 3 and 4 are different from those in 1 and 2 due to the rotation of C–C single bond in bpe. Polymer 5 exhibits an interesting 3D porous framework with 2-fold interpenetration, in which intriguing 1D double helix chains are observed. The photoluminescence properties of 1 and 2 in the solid-state at room temperature are investigated. In addition, variable-temperature magnetic data show weak antiferromagnetic behavior in 3–5.Five new transition metal coordination polymers based on flexible H2tzda and bpe have been hydrothermally synthesized and characterized by X-ray diffraction, luminescent emission spectra and low-temperature magnetic measurements, respectively.

Three inorganic–organic supramolecular networks based on 2-[(4,6-dimethylpyrimidinyl)-2-thio] acetic acid (HL) and Zn(II), Ag(I) and Cu(II) salts have been prepared and structurally characterized by single-crystal X-ray diffractions. Mononuclear complex [ZnL2(1,2-DAP)]·2H2O (1) (1,2-DAP = 1,2-diaminopropane) exhibits a three-dimensional cavity architecture through hydrogen bonds and π–π interaction. The crystal structure of (AgL)n (2) consists of two-dimensional brick-wall framework. [Cu2L4(CH3OH)2]·3CH3OH (3) contains dinuclear copper units, which are bridged by four acetate groups. Electrochemical behaviors have been systematically investigated by different electrochemical methods. Complex 3 shows a pair of quasi-reversible redox peaks. The electrode process is controlled by diffusion. The diffusion coefficient (D) for 3 is about 10−6 cm2 s−1. The electron transfer number (n) and the transfer coefficient (α) are 2 and 0.33, respectively.

In this study, the predominant H2-producing bacterial strain was isolated from a bio-reactor fed with lesser panda manure, and identified as Clostridium sp. based on 16S rDNA gene analysis. The bio-pretreatment of corn stalk was found to be most effective at ambient temperature of 25 °C, microbe additive of 7.5 g/kg with saccharification period of 15 days under the anaerobic condition. The maximum H2-production yield (176 ml H2/g-TS) and rate (18 ml H2/g-TS h−1) were achieved at operating pH 5.5, 36 °C and substrate concentration of 15 g/L. The H2 content in the biogas was 44.3–57.2% (v/v) and there was no significant methane gas observed. During the optimal period of H2 production, the ORP values stayed in the lower level ranging from −445 mV to −455 mV. The results indicated that the effluent was composed mostly of butyric acid and acetic acid, which accounted for 70–80% of total VFAs, followed by small amounts of butanol and propionate.

A hydrogen producing strain newly isolated from anaerobic sludge in an anaerobic bioreactor, was identified as Clostridium beijerinckii Fanp3 by 16S rDNA gene sequence analysis and detection by BioMerieux Vitek. The strain could utilize various carbon and nitrogen sources to produce hydrogen, which indicates that it has the potential of converting renewable wastes into hydrogen. In batch cultivations, the optimal initial pH of the culture medium was between 6.47 and 6.98. Using 0.15 M phosphate as buffer could alleviate the medium acidification and improve the overall performance of C. beijerinckii Fanp3 in hydrogen production. Culture temperature of 35 °C was established to be the most favorable for maximum rate of hydrogen production. The distribution of soluble metabolic products (SMP) was also greatly affected by temperature. Considering glucose as a substrate, the activation energy (Ea) for hydrogen production was calculated as 81.01 kcal/mol and 21.4% of substrate energy was recovered in the form of hydrogen. The maximal hydrogen yield and the hydrogen production rate were obtained as 2.52 mol/mol-glucose and 39.0 ml/g-glucose h−1, respectively. These results indicate that C. beijerinckii Fanp3 is an ideal candidate for the fermentative hydrogen production.

Hydrothermal reactions of 1-aminoethylidenediphonic acid { CH3C(NH2)(PO3H2)2, H4aedp} with CaCl2, Sr(NO3)2 and Pb(AC)2·3H2O resulted in three new main group metal diphosphonate coordination polymers. Namely, Ca[CH3C(NH3)(PO3H)2]2[CH3C(NH3)(PO3H)(PO3H2)]2 (1), Sr[CH3C(NH2) (PO3H)2(H2O)]·H2O(2) and Pb[CH3C(NH3)(PO3H)(PO3)]·H2O(3). The calcium (II) ion in complex 1 is octahedrally coordinated by six phosphonate oxygen atoms from six diphosphonate ligands, four of them in a bidentate and two in a monodentate fashion. The neighboring calcium ions are linked by pairs of P–O–P bridges, resulting in a pseudo-one-dimensional chain along the c axis. Complex 2 is the first example of the strontium phosphonate which has not been synthesized and structurally characterized before. It features a layered structure, in which strontium(II) ions are eight coordinated by an aqua ligand and seven phosphonate oxygen atoms from four diphosphonate ligands, two SrO8 polyhedra are bridged into a demeric unit by a pair of oxygen atoms and two diphosphonate groups. And such dimers are interconnected by the P–O–P bridges and O bridges to form complicated layers parallel to the ab plane. Complex 3 also has a layered structure in which the lead (II) ions are six coordinated by six phosphonate oxygens from four equivalent diphosphonate ligands. Each pair of PbO6 octahedra forms a dimeric unit via O–O edge-sharing and such dimeric units are interconnected via O–O edge-sharing to form a one-dimensional chain along the b-axis. These 1D chains are further bridged by the phosphonate ligands to form a complicated layer parallel to the bc plane. This type of layered structure has not been reported in other lead phosphonates.

Hydrothermal reactions of rare earth ions(III) with a flexible building unit (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid (H2tzda) lead to five novel coordination polymers with 1D chain and 3D network structures, namely, {[Y2(tzda)3(H2O)10] · 5H2O}n (1) and [Ln2(tzda)3(H2O)5]n [Ln = Er (2), Pr (3), Nd (4), Eu (5)]. Compound 1 has one-dimensional ribbon-like chain structure constructed by [Y2(tzda)3] units through the syn–anti bidentate bridging mode of carboxylate groups. Compounds 2–5 possess compact three-dimensional network structures which are made up of [Ln2(tzda)3] (Ln = Er, Pr, Nd and Eu) units bridged by carboxylate groups. In these compounds, the flexible tzda2− ligand is versatile and displays six different coordination fashions to meet the requirement of the coordination preference of the metal center. Furthermore, the magnetic behaviors for 2–5 in the temperature range of 5.0–300 K and photoluminescent property of 5 are significantly investigated in this paper.Hydrothermal reactions of rare earth ions(III) with a flexible ligand (1,3,4-thiadiazole-2,5-diyldithio)diacetic acid (H2tzda) lead to five novel coordination polymers, {[Y2(tzda)3(H2O)10] · 5H2O}n (1) and [Ln2(tzda)3(H2O)5]n [Ln = Er (2), Pr (3), Nd (4) and Eu (5)]. In these compounds, tzda2− displays six different coordination modes. The magnetic behaviors for 2–5 in the temperature range of 5.0–300 K and photoluminescent property of 5 are significantly investigated in this paper.

A novel copper organodiphosphonate complex containing a second ligand 4,4′-bipyridine (4,4′-bpy) based on 1-aminoethylidenediphosphonic acid (H4aedp), Cu4(aedp)2(4,4′-bpy)(H2O)4 (1), has been synthesized under hydrothermal conditions. Complex 1 adopts a three-dimensional framework structure assembled from {Cu4(aedp)2(H2O)4} layers and 4,4′-bpy bridges. Each {Cu4(aedp)2(H2O)4} unit consists of three crystallographically distinct Cu atoms. The Cu(1) atom has a distorted square pyramidal geometry, whereas the Cu(2) and Cu(3) atoms have a distorted elongated tetragonal octahedral geometry. The magnetic studies indicate that complex 1 show typical antiferromagnetic behaviors at low temperature, which is attributed to the superexchange couplings between Cu(II) centers through μμ–O bridge in the phosphonate layers. Crystal data for 1: triclinic, space group P1¯, a=8.0931(16)a=8.0931(16), b=13.567(3)b=13.567(3), c=6.2185(12)Åc=6.2185(12)Å, α=90.55(3)α=90.55(3), β=96.97(3)β=96.97(3), γ=78.50(3)°γ=78.50(3)°, V=664.1(2)Å3V=664.1(2)Å3, Z=2Z=2.A novel copper diphosphonate complex Cu4(aedp)2(4,4′-bpy)(H2O)4 has been hydrothermally synthesized and characterized, which adopts a three-dimensional framework structure assembled from {Cu4(aedp)2(H2O)4} layers and 4,4′-bpy bridges. It shows typical antiferromagnetic behaviors at low temperature.

Two novel metal dithiolene complexes, namely NtBu4[M(BNT)2] [M = Co/Ni, (BNT = (R)-1, 1′-binaphthalene-2,2′-dithiol)], have been synthesized and characterized. An efficient homogeneous photocatalytic system was constructed by a combination of the noble-metal-free target complexes as water reduction catalysts, xanthene dyes as the photosensitizer and triethylamine (TEA) as the sacrificial electron donor under irradiation with visible light (λ > 420 nm). Maximum H2 evolution of 495 and 676 turnovers (vs. catalyst) were recorded for each catalyst, respectively, under optimal conditions in CH3CN/H2O (1:1, v/v) after 4 h of irradiation. Furthermore, the mechanism of the H2 evolution was also briefly discussed alongside fluorescence spectra and cyclic voltammetry studies.

An uncommon butterfly-like tetranuclear copper(II) cluster with the formula {[Cu4(μ3-OH)2(μ4-Cl)(H2O)2(L)2]·Cl(H2O)7}n (1) (H2L = 1,2-bis[3-(1,2,4-triazolyl)-4-amino-5-carboxylmethylthio]ethane) has been synthesized. Compound 1 exhibits interesting anion exchange characteristics, in which both guest and coordinated Cl− can be replaced by I− or NO3− in water. Furthermore, a high catalytic selectivity to produce poly(phenylene ether) by the oxidative coupling of 2,6-dimethylphenol in water is found to be 74% for 1 and 87% for the anion-exchanged product 1-MIx, respectively. Additionally, the antiferromagnetic interaction among Cu ions for compound 1 is also found.

Two new binuclear cobalt complexes, namely {[Co(dmgH)(dmgH2)]2L1} (I) and {[Co(dmgH)(dmgH2)]2L2} (II) (dmgH = dimethylglyoximate monoanion; dmgH2 = dimethylglyoxime, L1 = 1,3-bis(4-pyridyl)propane), L2 = 1,3-bis(imidazol-1-ylmethyl)benzene), have been synthesized by the self-assembly of [Co(dmgH)(dmgH2)] and L1 or L2, respectively. An efficient photocatalytic system was constructed by combining a noble-metal-free cobalt complex as the catalyst with Eosin Y dye (EY2−) as the photosensitizer to give an efficient H2 generating system under visible-light irradiation (λ > 420 nm) using triethanolamine (TEOA) as a sacrificial electron donor. The maximum amount of H2 generated was 1013 TON for I and 1134 TON for II over a 2 h irradiation period (λ > 420 nm) under the conditions of pH 8.0, 5% TEOA (v/v), an EY2− concentration of 4.0 × 10−4 M and a catalyst concentration of 4.0 × 10−4 M in the mixed solvent system of CH3CN–H2O (3:1, v/v). In addition, the mechanism of H2 generation in the photolysis system was briefly discussed.