•We study the nonlinear absorption properties of SnS2 and SnSe2 for the first time.•We find SnS2 have excellent optical limiting for the first time.•The optical limiting threshold Fth of SnS2 is only about 0.23 J/cm2.Tin-based dichalcogenides such as SnS2 and SnSe2 have attracted wide attention due to their significant potential for the next-generation optoelectronic and photonic devices in nanotechnology. We investigate the nonlinear absorption of SnS2 and SnSe2 nanosheets using the Z-scan technique with nanosecond pulse and picosecond pulse at 532 nm for the first time. Z-scan measurement reveals that SnS2 nanosheets dispersions exhibit reverse saturable absorption (RSA) behavior under different pulses, which is in contrast to the saturable absorption (SA) observed in the SnSe2 nanosheets dispersions resulted from different band gaps. The nonlinear absorption coefficient (β) and the figures of merit (FOM) of SnS2 dispersed in ethanol with linear transmittances of 0.75 at input energy of 6.16 μJ in the nanosecond regime are 12.78 × 10−10 m/W and 8.71 × 10−11 esu⋅cm, respectively. As for SnSe2 nanosheet dispersions, β and FOM are −12.58 × 10−10 m/W and 11.98 × 10−11 esu⋅cm at the same input energy, respectively. The RSA behavior coupled to the smaller optical limiting threshold Fth (0.23 J/cm2) proves SnS2 a promising 2D material for protecting sensitive optical components or eyes from laser-induced damage. The SA performance indicates SnSe2 nanosheets prospective candidates for high-performance nanoscale nanophotonic devices like optical switches.The nonlinear absorption performance of SnX2 (X = S, Se) was measured by Z-Scan technique at nanosecond pulse and picosecond pulse, the results show that SnS2 nanosheets have excellent optical limiting property and optical limiting threshold Fth is about 0.23 J/cm2. However, SnSe2 nanosheets exhibit saturable absorption behavior.Download high-res image (171KB)Download full-size image

Using plant materials as templates is a convenient and low-cost route to prepare solid base catalysts with high specific surface area. In this study, a series of biomorphic calcium oxide/carbon catalysts have been prepared via an in situ transformation technique using rice grains as a template and carbon precursor. The resulting CaO/carbon materials are spindly shaped catalysts and show a high specific surface area and strong basicity. In the methylation of cyclopentadiene, these CaO/carbon materials exhibit a higher catalytic performance than MgO/carbon materials and CaO prepared by directly calcining the CaO precursor. Moreover, the regeneration of deactivated catalyst is studied, and steam or CO2 treatment at high temperature is found to be very effective for this carbon supported catalyst, and can even promote the catalytic activity. A possible mechanism for the deactivation and regeneration of the CaO/carbon materials has been proposed.

•Mesoporous graphitic C3N4 was prepared via a hard templating route.•A novel cross-linked bimodal mesoporous SBA-15 is used as a hard template.•Numerous mesopore openings are formed on the surfaces of mesoporous g-C3N4.•Mesoporous g-C3N4 shows a high specific surface area and a large pore volume.•Mesoporous g-C3N4 exhibits the high photocatalytic performance with visible light.Mesoporous graphitic C3N4 has been synthesized using a novel cross-linked bimodal mesoporous (CLBM) SBA-15 as a hard template. This cross-linked bimodal mesoporous SBA-15 template was prepared by adjusting the pH to alter the copolymer micelle size. The resulting mesoporous g-C3N4 replicates the morphology of the mesoporous silica template, and numerous pore openings are formed on the surfaces. The mesoporous g-C3N4 exhibits a high specific surface area and a large pore volume. The photocatalytic degradation activity of methyl orange on mesoporous g-C3N4 is nearly 15.3 times as high as that on bulk-g-C3N4 under visible light irradiation. The high photocatalytic performance of this sample is due to the high specific surface area and more readily accessible active sites.

SBA-3/cotton fiber composite materials have been in situ synthesized via a confinement self-assembly process by using cetyltrimethyl ammoniumbromide (C16H33(CH3)3NBr, CTAB) as a template to control the mesostructure and cotton fiber, a green and facile material, as a matrix to control the morphology. This kind of composite materials present the morphology of cotton fibers, and SBA-3 particles cover the surfaces of cotton fibers. Compared with powdery SBA-3, smaller silica particles are formed on these composite materials, which is beneficial for enhancing the availability of pores in mesoporous silica; and the cotton fibers promote the dispersion of functional modified guest in mesoporous silica. After modification with tetraethylenepentamine, these SBA-3/cotton fiber composite materials exhibit considerable CO2 adsorption capacity and stable cyclic adsorption–desorption performance. These composite materials can be directly used as cheaper shaped composites for practical CO2 capture, and this synthetic route has the potential to prepare some functional devices.Graphical abstractHighlights► In situ synthesis of shaped CO2 adsorbent via a confinement self-assembly process. ► Flexible netlike cotton fibers promote the dispersion of SBA-3 and TEPA. ► High efficiency of pore promote the CO2 adsorption capacity. ► These composites display stable cyclic adsorption–desorption performance.

A novel biomorphic nanocrystal-assembled mesoporous (NAM) magnesium oxides have been synthesized via an exotemplating pathway using cotton fibres as template and magnesium acetate as MgO precursor. These mesoporous MgO materials replicate the microtubular or zonal structure of the cotton morphology, and their frameworks are constructed by plenty of uniform MgO nanocrystals, which are different from those of the cotton template and reference MgO prepared by directly thermal-decomposition of MgO precursor. The mesoporous structure with narrow slit-like pores can be formed, if suitably chosen amounts of precursor magnesium acetate are used. These biomorphic NAM MgO materials have high surface areas, exhibit high selectivity in the catalytic decomposition of isopropanol, and display their potential for an effective basic catalyst or support.

Amphiphilic ODA/HY and ODA/ Hβ zeolites have been prepared via chemically coating octadecylamine (ODA) with alcohol as solvent. IR and titrimetric results indicate that ODA molecules are chemisorbed on the acidic sites in zeolite, showing the higher thermostability and alcohol-resistance. These amphiphilic zeolites contain both the hydrophobic and hydrophilic groups, orient at the liquid-liquid phase-boundary in both cyclohexane/water and water/carbon tetrachloride systems, and exhibit the potential to be used in the phase-boundary catalysis and adsorption. No by-products with strong acidity are formed in this approach, therefore, it can be used to prepare amphiphilic acidic zeolites with low Si/Al ratio.

The methylation of cyclopentadiene with methanol has been studied over Al2O3 and KOH promoted MgO and unpromoted MgO. The dehydrogenation of methanol to formaldehyde was found to be a key-step in the generation of the active methylating species on these solid bases. The modification with Al2O3 or KOH favors the formation of methylcyclopentadienes and elevates the activity of MgO based on different reasons: introduction of acidic sites for Al2O3/MgO and superbasic effect for KOH/MgO. These catalysts present different deactivation behaviors due to the different surface acid–base properties. The heavy coking of cyclopentadiene on basic sites is responsible for the rapid deactivation of KOH/MgO along the catalytic test at 773 K. However, the coking can be well suppressed at 723 K, and KOH/MgO exhibits the catalytic performance apparently superior to MgO and Al2O3/MgO.Catalytic performance of MgO in cyclopentadiene methylation was promoted by Al2O3 via introducing acidic sites or KOH via superbasic effect. Dehydrogenation of methanol is a key step.Download high-res image (73KB)Download full-size image

Using plant materials as templates is a convenient and low-cost route to prepare solid base catalysts with high specific surface area. In this study, a series of biomorphic calcium oxide/carbon catalysts have been prepared via an in situ transformation technique using rice grains as a template and carbon precursor. The resulting CaO/carbon materials are spindly shaped catalysts and show a high specific surface area and strong basicity. In the methylation of cyclopentadiene, these CaO/carbon materials exhibit a higher catalytic performance than MgO/carbon materials and CaO prepared by directly calcining the CaO precursor. Moreover, the regeneration of deactivated catalyst is studied, and steam or CO2 treatment at high temperature is found to be very effective for this carbon supported catalyst, and can even promote the catalytic activity. A possible mechanism for the deactivation and regeneration of the CaO/carbon materials has been proposed.