Zuo-Ren Nie

Highly Hydrothermally Stable Microporous Silica Membranes for Hydrogen Separation

Fluorocarbon-modified silica membranes were deposited on gamma-Al2O3/alpha-Al2O3 supports by the sol-gel technique for hydrogen separation. The hydrophobic property, pore structure, gas transport and separation performance, and hydrothermal stability of the modified membranes were investigated. It is observed that the water contact angle increases from 27.2+/-1.5 degrees for the pure silica membranes to 115.0+/-1.2 degrees for the modified ones with a (trifluoropropyl)triethoxysilane (TFPTES)/tetraethyl orthosilicate (TEOS) molar ratio of 0.6. The modified membranes preserve a microporous structure with a micropore volume of 0.14 cm3/g and a pore size of approximately 0.5 nm. A single gas permeation of H2 and CO2 through the modified membranes presents small positive apparent thermal activation energies, indicating a dominant microporous membrane transport. At 200 degrees C, a single H2 permeance of 3.1x10(-6) mol m(-2) s(-1) Pa(-1) and a H2/CO2 permselectivity of 15.2 were obtained after proper correction for the support resistance and the contribution from the defects. In the gas mixture measurement, the H2 permeance and the H2/CO2 separation factor almost remain constant at 200 degrees C with a water vapor pressure of 1.2x10(4) Pa for at least 220 h, indicating that the modified membranes are hydrothermally stable, benefiting from the integrity of the microporous structure due to the fluorocarbon modification.

Hierarchically structured layered-double-hydroxide@zeolitic-imidazolate-framework derivatives for high-performance electrochemical energy storage

CoAl-based layered-double-hydroxide@zeolitic-imidazolate-framework-67 (LDH@ZIF-67) was fabricated via a hydrothermal synthesis of LDH film on Ni substrate followed by the in situ growth of ZIF-67. Its derivatives, MMO@Co3O4, spinelle@C and LDH@CoS with hierarchical structures were obtained by the subsequent oxidation, carbonization and sulfurization of LDH@ZIF-67, respectively, which exhibit distinct specific capacitances of 692, 781 and 1205 F g−1 at a discharge current density of 1 A g−1. Interestingly, these derivatives retained hierarchical structures with large surface area, which ensures that the majority of exposed active species can participate in the charge–discharge process and thus effectively contribute to total capacitances. The synergistic effect from fast electronic transfer reduces reversible ion accumulation at the interface, which imparts LDH@ZIF-67 derivatives improved electrochemical activities, in contrast to conventional bulk MOF derivatives. In addition, it was found that the combination of the remarkable electrical conductivity of sulfides (compared with their oxide counterparts) and the strong electronic coupling between LDH and CoS can facilitate fast electron transfer. As a result, LDH@CoS exhibits an excellent specific energy of 44.5 W h kg−1 at a current density of 20 A g−1, as well as good capacitance retention of 88.5% after 2000 cycles. This work thus demonstrates a feasible strategy for the design and fabrication of LDH@MOF derived composites as SCs components, which is applicable in constructing other novel electrode materials with hierarchical structures for applications in energy storage systems.

A magnetic mesoporous SiO2/Fe3O4 hollow microsphere with a novel network-like composite shell: synthesis and application on laccase immobilization

The magnetic mesoporous SiO2/Fe3O4 hollow microspheres, which have a unique network-like shell constructed with magnetic Fe3O4 nanorods and mesoporous SiO2, were successfully prepared by the co-condensation of tetraethoxysilane in the presence of cetyltrimethylammonium bromide and 1,3,5-triisopropylbenzene. The composite microspheres were utilized as supports for laccase immobilization. The composite microsphere has high surface area (772xa0m2xa0g−1) and large pore volume (0.83xa0cm3xa0g−1). The obtained microspheres exhibit relatively high saturated magnetization (13.6xa0emuxa0g−1). The composite mesoporous microspheres used to immobilize laccase as support have a notable laccase immobilization (689xa0mgxa0g−1) for per gram pure mesoporous SiO2 in the composite microspheres, which is much larger than those reported in the literature. The activity of immobilized laccase has good pH stability and thermal stability. It is further demonstrated that the immobilized laccase exhibited a good catalytic performance when they were used to react with the 2,4-dichlorophenol solution. The degradation rate and removal rate of the 2,4-dichlorophenol is 52.31 and 81.64xa0%, respectively.Graphical Abstract

Hydrophobic silica aerogel derived from wheat husk ash by ambient pressure drying

Silica aerogels from wheat husk ash (WHA) were prepared via a sol–gel process by ambient pressure drying. Silica was extracted from WHA by NaOH solution to form sodium silicate, which was used as precursor for aerogels. Silica wet gels were synthesized by resin-exchange-alkali-catalysis of the sodium silicate solution, followed by solvent exchange with ethanol (EtOH) and hexane in turn. Consequently, a mixture of trimethylchlorosilane, EtOH and hexane was used for surface modification of the wet gels in order to obtain hydrophobic silica aerogels. The density, pore structure, hydrophobic property and thermal insulation property of the obtained silica aerogels were investigated in detail. The results show that the formation of silica aerogels can be successfully realized at a SiO2/H2O weight ratio varying from 0.065 to 0.167. Silica aerogels possess a desirable pore structure with a surface area ranging from 513xa0±xa05 to 587xa0±xa06xa0m2/g, a pore volume from 2.3xa0±xa00.3 to 4.0xa0±xa00.1xa0cm3/g and a pore size from 9xa0±xa02 to 15xa0±xa01xa0nm, an outstanding hydrophobic property with a water contact angle of 147xa0±xa00.1° and a distinguished thermal insulation property with a low thermal conductivity ranging from 0.009xa0±xa00.0001 to 0.012xa0±xa00.0002xa0W/(m·K).Graphical Abstract

Visible-light responsive MOF encapsulation of noble-metal-sensitized semiconductors for high-performance photoelectrochemical water splitting

A strategy that visible-light responsive zeolitic-imidazolate-framework-67 (ZIF-67) encapsulates noble-metal sensitized semiconductors, ZnO@M (M = Au, Pt, and Ag) to fabricate composite catalysts for photoelectrochemical (PEC) water splitting is proposed. The obtained ZnO@M@ZIF-67 catalysts have good catalytic performance, particularly, the ZnO@Au@ZIF-67 exhibits quite improved photoconversion efficiency and photocurrent density, superior to most of the reported photoelectrode catalysts. This can be attributed to the wider solar spectra harvesting capability originating from visible-light responsive ZIF-67 and UV-light active ZnO. Simultaneously, their integration enables interfacial electrons in the ZIF-67 shell to easily transfer to the ZnO@Au core, providing good electron–hole separation. In addition, the porous ZIF-67 as a protective shell ensures structural robustness, while maintaining fast ion or gas bubble diffusion through its pores, accounting for stable and excellent PEC performance.

Activity enhancement of Microperoxide-11 immobilized on nanospheres with a nanosize Co3O4 core and a periodic mesoporous organosilica shell

Core-shell nanospheres with a nanosize Co3O4 core and a periodic mesoporous organosilica (PMO) shell were fabricated by the packing and self-assembly of nanosize Co3O4 particles–surfactant–organosilica complexes based on the S+I− pathway under basic conditions. The amount of Co3O4 nanoparticles is crucial to the formation of core–shell nanospheres. The obtained nanospheres possess a uniform particle size of 130 nm, a high surface area of 474.1 m2g−1 and a large pore volume of 0.68 cm3g−1, which are highly advantageous to the immobilization of Microperoxidase-11 (MP-11). The presence of Co3O4 nanoparticles could enhance the activity of immobilized MP-11, probably due to their peroxidase activity.

Catalase immobilized on siliceous mesocellular foam with controlled window size

Siliceous mesocellular foam (MCF) with tunable cell and window size was synthesized by the acid catalyzed sol–gel reaction of tetraethoxysilane in the presence of triblock copolymer Pluronic P123 (EO20PO70EO20) as structure-directing agent. The cell’s size of MCF is increased with the increase of 1,3,5-trimethylbenzene amount, while the window’s size of MCF could be tailored between 4 and 18.2xa0nm without affecting the cells size by adding of NH4F. The obtained MCF materials were employed as carriers for catalase immobilization. FT-IR spectra and N2 sorption show that the catalase is immobilized into the mesopores of MCF. MCF with window size of 12.9xa0nm shows high catalase loading and activity, suggesting that matching the window’s size with enzyme molecular diameter is a critical factor in attaining efficient immobilization since smaller window size prevents larger enzyme from entering the pore and larger window size causes the leakage of enzyme. The thermal and storage stabilities of the immobilized catalase were also improved due to the shield of the mesopores of MCF.

Controllable morphology and pore structure of micron-sized organic-inorganic hybrid silica spheres derived from silsesquioxane

Mesoporous organic–inorganic hybrid silica with ethylidene bridging group between two silicon atoms was prepared via a sol–gel and hydrothermal synthesis process by using silsesquioxane (1,2-bis(triethoxysilyl) ethane, BTESE) as silicon source and triblock copolymer poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (P123) in combination with dodecyltrimethylammonium bromide (DTAB) as template. Factors that affect the morphology and pore structure of silica particles were investigated in detail by means of scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption. The results show that the sphericity and surface smoothness of organic–inorganic hybrid silica are distinctly enhanced with increasing amount of DTAB and hydrochloric acid. Meanwhile, suitable synthesis time and crystallization temperature are beneficial to the formation of silica spheres with improved sphericity. The organic–inorganic hybrid silica spheres prepared with a DTAB/BTESE molar ratio of 0.8, a HCl/BTESE molar ratio of 6, an aging time of 24xa0h and a crystallization temperature of 100xa0°C exhibit a particle size of around 1.7xa0µm, a high surface area of 1063.35xa0m2xa0g−1 and a narrow pore size distribution centered at 3.12xa0nm.Graphical Abstract

A rapid and low solvent/silylation agent-consumed synthesis, pore structure and property of silica aerogels from dislodged sludge

Dislodged sludge, a kind of industrial waste, was used as raw material to prepare silica aerogels via ambient pressure drying. The effect of solvent exchange and surface silylation on the pore structure and property of the obtained materials was investigated in detail. If the ethanol and n-hexane exchange decreases to 8u2009h (two times, each time for 4u2009h) and 4u2009h (one time), respectively, and the volume ratio of ethanol/wet gel and n-hexane/wet gel reduces to 2 and 1, respectively, the obtained materials exhibit a desirable pore volume of 3.17u2009cm3/g, a water contact angle of 152.9° and a low thermal conductivity of 0.030u2009W/ (m·K). Further decreasing the mole ratio of silylation agent/SiO2 to 0.5 and the silylation time to 6u2009h results to silica aerogels with a pore volume of 3.44u2009cm3/g, a water contact angle of 144.5° and a low thermal conductivity of 0.032u2009W/ (m·K). A rapid synthesis (a total time of 50u2009h, from wet gel aging to ambient pressure drying) of silica aerogels has been realized and the consumption of solvent/silylation agents has been pronouncedly reduced without sacrificing the thermal insulation property of the obtained materials.Graphical Abstract

Mesoporous organosilicas with ultra-large pores: mesophase transformation and bioadsorption properties.

Large pore ordered mesoporous organosilicas (OMOs) with distinct mesophase structure was synthesized under low temperatures by the co-condensation of 1,2bis(triethoxysilyl)ethane (BTESE) and tetraethyl orthosilicate (TEOS) in acidic solution, using triblock copolymer F127 as a template and 1,3,5-trimethylbenzene (TMB) as a swelling agent. With the decrease of temperature, a mesophase transformation from 2D hexagonal structure (p6mm) via mesostructured cellular foam to a highly ordered 3D cubic structure (Fm3m) was evidenced by small angle X-ray diffraction (SAXS), transmission electron microscopy (TEM) and N(2) sorption. It reveals that the lower synthesis temperatures may influence the hydrolysis and condensation of silica species and the hydrophilic-hydrophobic property of F127, as well as the swelling capacity of F127 micelles with TMB, which resulting in a formation of large pores ordered mesoporous organosilicas with various mesostructures materials. Finally, the enzyme adsorption properties of the OMOs were investigated and the results showed that the OMOs with a 3D large pore structure and regular morphology is much more qualified for enzyme adsorption.