Mesostructured Cellular Foam Research Articles

Synthesis of Al-Containing Spherical Mesocellular Silica Foams with Different Pore Sizes and Their Applications as Catalyst Supports for Hydrodesulfurization of Dibenzothiophene

In the present work, a series of Al-containing spherical mesostructured cellular silica foams (SMCFs) with different ultra-large pore sizes were successfully synthesized by simply adjusting the mass ratio (x) of the swelling agent 1,3,5-trimethylbenzene (TMB) to P123. The as-synthesized Al-SMCFs-x were utilized as NiMo catalyst supports for the hydrodesulfurization of dibenzothiophene. The characterization results showed that, compared with other studied NiMo/Al-SMCFs-x catalysts, the NiMo/Al-SMCFs-1.25 catalyst exhibited higher sulfidation degree, higher dispersions of Ni and Mo species, shorter length, and lower stacking number of MoS2 slabs. It was also found that the NiMo/Al-SMCFs-1.25 catalyst possessed suitable physicochemical parameters [i.e., ultra-large pore size (27.5 nm), high surface area (383 m2 g−1), and large pore volume (1.34 cm3 g−1), resulting in the formation of more type II active sites with more brim active sites. Consequently, the NiMo/Al-SMCFs-1.25 catalyst displayed outstanding catalytic performance for the hydrodesulfurization of dibenzothiophene.

Salt-assisted synthesis of mesostructured cellular foams consisting of small primary particles with enhanced hydrothermal stability

Mesoporous silica materials have attracted considerable attention as adsorbents, catalyst supports, and drug delivery carriers due to their large surface area, high pore volume, and controllable pore size. To increase the adsorption or mass transport properties, large pore sized mesoporous silica is highly desired. Here, we demonstrate a new green synthetic route for obtaining salt-assisted mesostructured cellular foams (S-MCFs) using a triblock copolymer as a single structure-directing agent by addition of inorganic salt without using a hydrophobic pore expander. The S-MCF was composed of ∼27 nm cellular pores and 10 nm windows and had distinct pore walls and a cellular structure. S-MCFs showed an enhanced hydrothermal stability compared to other mesocellular silica. In addition, the primary particle size of the S-MCF was 100–300 nm, which is much smaller than that of previously reported mesostructured cellular foams (MCFs) and mesocellular silica foam (MSU-F). The adsorption study using a model protein revealed that small primary particle size in S-MCF is beneficial for mass transfer in a short period of time. Therefore, S-MCF may serve as a potential platform for higher mass transport or adsorption of large molecules with good stability.

Competitive adsorption of lysozyme and myoglobin on mesostructured cellular foam silica

A model of multicomponent multilayer adsorption has been developed to describe the simultaneous adsorption of lysozyme (14.3 kDa, pI = 11.35) and myoglobin (17.6 kDa, pI = 7.2) on mesostructured cellular foam (MCF) silica in 0.02 M potassium phosphate buffer at pH 7 and 25 °C. The mechanism of adsorption was proposed based on batch adsorption isotherms and flow microcalorimetry (FMC) traces for the enthalpy of adsorption. Thermodynamic derivations of Guggenheim–Anderson–deBoer (GAB) and Langmuir models were used to develop the model based on the proposed mechanism. Regression analysis demonstrated the effect of each of the proposed mechanistic equations.

Response Surface Optimization of Impregnation of Blended Amines into Mesoporous Silica for High-Performance CO2 Capture

We used the response surface method (RSM) to optimize the conditions for the impregnation of blended amines into mesostructured cellular silica foam (MSU-F) to prepare effective solid sorbents for CO2 capture. The effects of the amounts of tetraethylenepentamine (TEPA), diethanolamine (DEA), and methanol (MeOH) in the wet impregnation mixture on the amounts of CO2 adsorbed were investigated. The influences of these three independent variables and their interactions were determined using the RSM; the optimum amounts of TEPA, DEA, and MeOH were 1.33 g (7.03 mmol), 0.85 g (8.08 mmol), and 58.2 g, for the preparation of 3 g of sorbent, respectively. Under the adsorption conditions of 40 °C and 100 kPa CO2, the optimum sorbent showed fast kinetics and an excellent CO2 adsorption of 5.64 mmol/g; the value predicted by the RSM model was 5.67 mmol/g. Analysis of variance and the coefficient of determination (R2 = 0.9525) showed the utility of the approach used in this study to optimize the conditions for preparin...

Mesostructured cellular foams modified by niobium or tantalum and functionalized with (3-mercaptopropyl)trimethoxysilane – Raman inspired reduction of synthesis time

The synthesis of mesostructured cellular foams (MCF) modified by niobium or tantalum source and functionalized with MPTMS (3-mercaptopropyl)trimethoxysilane was monitored in situ by Raman spectroscopy. The results from Raman monitoring prompted us to check for a possibility of shorter time synthesis of mesostructured cellular foams. A series of MCFs materials prepared using different times of gel mixing (5h and standard 20h) were synthesized. The samples obtained were characterized by N2 adsorption/desorption, XRD, TEM, XRF, elemental analysis, UV–Vis, FTIR and amperometric titration. The effects of niobium and tantalum on the rate and efficiency of thiol oxidation as well as on the time of silica formation were explored. The most important outcome of the study is the evidence of the formation of MCFs materials having strong Brønsted acidic centers in a shorter preparation time. SO3H groups form faster than in MP-MCF material in the presence of niobium or tantalum in the synthesis gel. The extension of synthesis time for silica and tantalosilicate samples leads to more efficient oxidation of thiol species. This feature does not depend on the synthesis time of niobiosilicate materials.

Aldehyde-functionalized mesostructured cellular foams prepared by copolymerization method for immobilization of penicillin G acylase

Aldehyde-functionalized mesostructured cellular foams (A-MCFs) were successfully prepared by copolymerization of vinyl groups on the surface of vinyl-functionalized mesostructured cellular foams (V-MCFs) with methacrolein, and used for covalent immobilization of penicillin G acylase (PGA). Effects of functionalization with the organo-functional groups on the physicochemical properties of V-MCFs and A-MCFs, and the enzymatic activity and the operational stability of the immobilized PGA were investigated. A-MCFs-15% sample retains the characteristic ultra-large and continuous 3D mesoporous structure of MCFs with high surface area and large pore volume, which is beneficial for immobilization of PGA and diffusion of substrates and products, and thus results in high enzymatic activity of the immobilized PGA. PGA is immobilized covalently on A-MCFs sample via the reaction to produce Schiff’s base between the free amino groups of lysine residues of PGA and the aldehyde groups on the surface of A-MCFs, which greatly increases the operational stability of the immobilized PGA. PGA/A-MCFs-15% sample shows the initial enzymatic activity of 9531Ug−1 and retains 87% of its initial activity after recycled for ten times.

Siliceous mesostructured cellular foams/poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) composite biomaterials for bone regeneration.

Osteoinductive and biodegradable composite biomaterials for bone regeneration were prepared by combining poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) with siliceous mesostructured cellular foams (SMC), using the porogen leaching method. Surface hydrophilicity, morphology, and recombinant human bone morphogenetic protein 2 adsorption/release behavior of the SMC/PHBHHx scaffolds were analyzed. Results of scanning electron microscopy indicated that the SMC was uniformly dispersed in the PHBHHx scaffolds, and SMC modification scaffolds have an interconnected porous architecture with pore sizes ranging from 200 to 400 μm. The measurements of the water contact angles suggested that the incorporation of SMC into PHBHHx improves the hydrophilicity of the composite. In vitro studies with simulated body fluid show great improvements to bioactivity and biodegradability versus pure PHBHHx scaffolds. Cell adhesion and cell proliferation on the scaffolds was also evaluated, and the new tools provide a better environment for human mesenchymal stem cell attachment, spreading, proliferation, and osteogenic differentiation on PHBHHx scaffolds. Moreover, micro-computed tomography and histological evaluation confirmed that the SMC/PHBHHx scaffolds improved the efficiency of new bone regeneration with excellent biocompatibility and biodegradability and faster and more effective osteogenesis in vivo.

Synthesis of large-pore mesostructured cellular foam silica spheres for the adsorption of biomolecules.

Mesostructured cellular foam (MCF) silica spheres with different textual parameters were synthesized using a triblock copolymer as a template. The effects of acid concentration and aging time on the window size and morphology were discussed. Besides, the adsorption performances of lysozyme and bovine serum albumin on the blank MCF with different window size and aminopropyl-modified MCFs were studied. The adsorption capacity and rates were shown to be dependent on the window size and surface chemical properties of the adsorbents. In particular, the MCF with window size of 15.2 nm showed fast adsorption for lysozyme with an adsorption capacity of 500 mg/g in 10 min. Furthermore, it has been shown that MCF spheres are potential materials in the separation of biomolecules because of their chemical tunable surface and molecular sieve properties.

Dominated Effect Analysis of the Channel Size of Silica Support Materials on the Catalytic Performance of Immobilized Lipase Catalysts in the Transformation of Unrefined Waste Cooking Oil to Biodiesel

Three mesoporous silica materials with various channel sizes and structures were employed to prepare immobilized lipase catalysts for the transesterification of unrefined wasted cooking oil (UWCO) to biodiesel at room temperature. The channel size of support material was found to be the key point to obtain high initial specific activity and high sustainability of activity of the immobilized lipase catalysts. A SBA-15 material with appropriate channel size (14.0 nm) demonstrates the best capacity of lipase. The immobilized catalyst with the SBA-15 material shows much higher activity and sustainability of activity than the immobilized catalysts with a MCM-41 material (channel size 1.8 nm) and a mesostructured cellular foam (MCF) material (channel size 28.0 nm) as support materials in the transformation of UWCO to biodiesel. After 60 h of reaction at 28 °C, a fatty acid methyl ester (FAME) yield up to 80.1 and 71.8 % of initial specific activity can be achieved using SBA-15-immobilized lipase.

Aldehydepropyl-functionalized mesostructured cellular foams: Efficient supports for immobilization of penicillin G acylase

Abstract The aldehydepropyl-functionalized mesostructured cellular foams (CHO-MCFs) were prepared by post-synthetical functionalization of MCFs with trimethoxysilylpropanal (TMSP), and used as efficient supports for immobilization of penicillin G acylase (PGA). The physicochemical properties of CHO-MCFs were characterized by SAXS, nitrogen sorption, TEM, elementary analysis, solid state 29 Si MAS NMR, FT-IR spectroscopy and thermogravimetry. The results show that the aldehydepropyl groups have been grafted successfully on the surface of MCFs, and after functionalization, the BET surface area and pore volume of CHO-MCFs decrease, but the ultra-large and continuous 3D mesoporous structure of CHO-MCFs are retained to be beneficial for immobilization of PGA with large size and diffusion of substrates and products. PGA is immobilized covalently on CHO-MCFs via the reaction to produce Schiff's base between the free amino groups of lysine residues of PGA and the aldehyde groups on the surface of CHO-MCFs, which greatly increases the operational stability of the immobilized PGA with little activity loss due to the short-chain groups of aldehydepropyl grafted on the surface of CHO-MCFs. PGA/CHO-MCFs-10 shows the immobilization yield of 57.6%, the specific activity of 22.2 U/mg and the initial enzymatic activity of 8895 U/g, and retains 93.0% of its initial enzymatic activity after recycled for 10 times.

Three-phase catalytic system of H2O, ionic liquid, and VOPO4-SiO2 solid acid for conversion of fructose to 5-hydroxymethylfurfural.

Efficient transformation of biomass-derived feedstocks to chemicals and fuels remains a daunting challenge in utilizing biomass as alternatives to fossil resources. A three-phase catalytic system, consisting of an aqueous phase, a hydrophobic ionic-liquid phase, and a solid-acid catalyst phase of nanostructured vanadium phosphate and mesostructured cellular foam (VPO-MCF), is developed for efficient conversion of biomass-derived fructose to 5-hydroxymethylfurfural (HMF). HMF is a promising, versatile building block for production of value-added chemicals and transportation fuels. The essence of this three-phase system lies in enabling the isolation of the solid-acid catalyst from the aqueous phase and regulation of its local environment by using a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]). This system significantly inhibits the side reactions of HMF with H2O and leads to 91 mol % selectivity to HMF at 89 % of fructose conversion. The unique three-phase catalytic system opens up an alternative avenue for making solid-acid catalyst systems with controlled and locally regulated microenvironment near catalytically active sites by using a hydrophobic ionic liquid.

Immobilization of penicillin G acylase on paramagnetic aldehyde-functionalized mesostructured cellular foams

Paramagnetic aldehyde-functionalized mesostructured cellular foams (PAMCFs), synthesized by grafting 3-aminopropyltriethoxysilane modified Fe3O4 (NH2-Fe3O4) nanoparticles with larger particle size than the window pore size of MCFs on the outer surface of aldehyde-functionalized mesostructured cellular foams (AMCFs), were investigated as efficient supports for immobilization of penicillin G acylase (PGA). The results show that NH2-Fe3O4 nanoparticles were successfully grafted on the outer surface of AMCFs and PGA molecules were mainly immobilized covalently on the inner surface of PAMCFs, which was because amino groups of NH2-Fe3O4 nanoparticles or PGA molecules reacted with aldehyde groups of AMCFs or PAMCFs to form imine bonds. PGA/PAMCFs-15 showed a rather high initial activity of 9563Ug−1 and retained 89.1% of its initial activity after recycled for 10 times. PGA/PAMCFs are easily recycled by magnetic field in order to replace tedious separation of high-speed centrifugation for mesoporous materials.

Au containing mesostructured cellular foams NbMCF and ZrMCF in selective oxidation of methanol to formaldehyde

Mesostructured cellular foams (MCF) doped with Nb or Zr were used as matrices for preparation of gold catalysts for oxidation of methanol. The focus was on the characterisation of Au–NbMCF and Au–ZrMCF materials as well as the effect of Au–Nb or Au–Zr interactions and the gold particle sizes on the activity of MCF catalysts in the selective MeOH oxidation towards formaldehyde. The samples prepared were characterised by XRD, N2 adsorption/desorption, TEM, UV–Vis, XPS, H2-TPR, FT-IR combined with the adsorption of pyridine and test reaction. The results allowed defining the location and coordination of Nb and Zr in the structure of MCF, the state of gold on the surface as well as the acid/base properties of the catalysts obtained.The results showed that the bifunctionalised gold catalysts containing Nb and Zr are highly active in selective methanol oxidation in the temperature range 523–623K. The presence of gold significantly enhanced the activity, whereas the Nb and Zr additives influenced the selectivity of the catalysts. Au–NbMCF and Au–ZrMCF appeared to be useful for the production of formaldehyde by methanol oxidation.

Paramagnetic epoxy-functionalized mesostructured cellular foams with an open pore system for immobilization of penicillin G acylase

Paramagnetic epoxy-functionalized mesostructured cellular foams (PEMCFs), prepared by reacting the epoxy groups grafted on the outer surface of epoxy-functionalized MCFs with the amino groups of l-cysteine modified on the surface of Fe3O4 nanoparticles, were characterized by SAXS, powder XRD, nitrogen sorption, TEM, FT-IR, TG, ICP-AES and magnetic susceptibility measurements, and investigated as the support for immobilization of penicillin G acylase (PGA). The results show that paramagnetic Fe3O4 nanoparticles were successfully grafted covalently on the outer surface of PEMCFs due to the larger particle size of Fe3O4 nanoparticles, and PGA was successfully immobilized covalently on the inner surface of PEMCFs. PGA immobilized on PEMCFs shows the highest initial activity and operational stability among those ever reported in the literatures, which had the initial activity of 8800Ug−1 and retained 94.5% of its initial activity after recycled for 10 times. PGA immobilized on PEMCFs can be easily recycled by the aid of an external magnetic field in order to replace the tedious separation of high-speed centrifugation.

Large pore mesostructured cellular silica foam coated magnetic oxide composites with multilamellar vesicle shells for adsorption

Herein, large pore mesostructured cellular silica foam coated magnetic oxide composites (MO@MCFs) with multilamellar vesicle shells (MO@MLVs) were obtained, which exhibited a large pore (>10 nm), strong magnetic response (38 emu g(-1)), excellent protein adsorption and slow drug-release capacity.

介孔碳泡沫分子筛的制备及其对葡萄糖氧化酶的吸附行为

以添加氟化铵改性的介孔二氧化硅泡沫分子筛为模板，糠醇为碳源，运用硬模板法制备不同孔结构的介孔碳泡沫分子筛。采用SEM观察、TEM观察及氮气吸附等手段对介孔碳泡沫分子筛的粒径及孔结构进行了表征。结果表明，经氟离子改性的介孔泡沫分子筛具有较小的颗粒粒径及较大的窗口孔径、胞体孔径和孔容，但比表面积较小。将所制备的介孔碳泡沫分子筛和介孔二氧化硅泡沫分子筛分别用于葡萄糖氧化酶的负载，介孔碳泡沫分子筛对葡萄糖氧化酶的吸附量远远大于相应的硅模板，表明酶分子和载体表面间的静电作用对负载过程有很大影响；同时，拥有较小粒径、较大胞体孔径和孔容的介孔碳泡沫分子筛表现出更大的葡萄糖氧化酶负载量，有望成为优良的酶载体材料。 By using fluorine-modified and original mesostructured cellular foam silica as templates, furfuryl alcohol as carbon precursors, carbonaceous mesocellular foams with different pore sizes were prepared, and then the grain sizes and pore structures of the samples were characterized by scanning electron microscope (SEM), Transmission Electron Microscopy (TEM) and nitrogen adsorption. It was found that fluorine-modified mesostructured cellular foams possessed the smaller particle sizes and specific surface area, but the larger windows and cell diameters and the larger pore volumes. All prepared samples were used as the carriers for immobilization of glucose oxidase. The loading amounts on carbonaceous mesocellular foams were much higher than on corresponding silicon templates, indicating that the immobilization process might be affected strongly by the electrostatic repulsion between the glucose oxidase molecules and carrier surface. Furthermore, carbonaceous mesocellular foam with smaller particle size, larger window size and pore volume showed the highest glucose oxidase loading amounts. It might be served as the prospective enzyme carrier material.

Synthesis of task-specific ionic liquids with grafted diglycolamide moiety. Complexation and stripping of lanthanides

Task-specific ionic liquids (TSILs) of a novel class, with the diglycolamide moietity grafted in the alkyl chain of imidazolium cation, were synthesized and characterized. Lanthanide complexation capabilities of TSILs as active components of solid phase extractants were evaluated by studies on the adsorption of lanthanides from aqueous solutions. The TSIL-based solid adsorbents prepared by immobilization of long-alkyl-chain TSILs in siliceous mesostructured cellular foams adsorb trivalent lanthanides. No extraction of lanthanides from aqueous solution into 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C6mim][Nf2T]) was observed at any acidity in the presence of these TSILs in the aqueous phase. This implies that TSILs suppress the extraction of lanthanides by formation of water-soluble complexes. The TSILs added to solvent extraction systems consisting of N,N,N′,N′-tetraoctyl-3-oxapentanediamide (TODGA) in [C6mim][Nf2T] and aqueous HNO3 solutions show very good stripping properties for lanthanides.

CO2 adsorption by amine modified siliceous mesostructured cellular foam (MCF) in humidified gas

A set of branched and linear polyethyleneimine (PEI) modified mesocellular siliceous foams (MCF) were evaluated as adsorbents for CO2 capture at modestly elevated temperatures under conditions that simulate the vacuum swing adsorption (VSA) process in humidified gas. Increasing the temperature was found to be beneficial for achieving reversible CO2 adsorption/desorption with reasonable capacities and rates. Under humid conditions, the materials lost 0–15% of their adsorption capacities in 0.5atm CO2 compared to under dry conditions at 105–115°C. The working capacity (0.025–0.15atm CO2) at 105°C was 2–17% higher under humid than under dry conditions. During cycling, the branched PEI adsorbent showed a gradual decrease in CO2 adsorption–desorption capacity under dry conditions, but the reduction in capacity was significantly reduced under wet conditions. The reduction in CO2 adsorption capacity was attributed to by-product formation, confirmed by IR, 13C CP-MAS NMR and EDS. In a humid environment, the formation of by-product was significantly reduced.

Anhydrous Proton Conducting Hybrid Proton Exchange Membrane by Phase Mode Atomic Force Microscopy

Hybridization of inorganic pillars and proton exchange membrane have been studied for increasing performance of proton exchange membrane fuel cell such as working under low relative humidity. For developing hybrid membrane, understanding of morphological structure is crucial. In this study, we synthesize silica meso-structured cellular foam (Si-MSU-F) and meso-structured aluminosilicate with hexagonal network (Al-MCM-41) and study morphological evolution of the membrane by using atomic force microscopy. When Nafion is composited with Si-MSU-F and Al-MCM-41, the hybrid membrane surface is evolved to different structure compare with the pristine Nafion. In addition, Si-MSU-F/Nafion shows different morphological structure as Al-MCM-41/Nafion hybrid membranes due to different hybridization mechanism between pillars and Nafion.

The production of biofuels additives on sulphonated MCF materials modified with Nb and Ta—Towards efficient solid catalysts of esterification

The aim of this work was to compare the properties of niobium (Si/Nb=118) and tantalum (Si/Ta=121) containing mesostructured cellular foams (MCF) modified with (3-mercaptopropyl) trimethoxysilane (MPTMS) in one-pot synthesis and the application of materials obtained in acetic acid esterification with glycerol. TaMCF materials were prepared for the first time. Catalysts were characterized by different techniques: N2 adsorption, XRF, elemental and thermal analyses, FTIR+pyridine adsorption and titration of acid sites. New catalysts have showed an excellent catalytic activity in the acetic acid esterification with glycerol to yield triacetylglycerol, also known as triacetin (a valuable additive for biodiesel composition). The influence of modifiers on the number and strength of acidic centres in the materials obtained was found and discussed in details in the paper. The strength of Brønsted acid centres (BAS) was estimated by the interaction of organosilane with transition metal via the use of methoxy groups from MPTMS. The highest concentration of acidic sites determined by NaOH titration was obtained on tantalum modified MCF, whereas the highest strength of BAS was observed on MP-NbMCF sample. The catalytic behaviour of MPTMS and Nb modified MCF samples was comparable to that observed for Amberlyst 15 and better than that of Nafion SAC 13. The materials obtained could be reused and showed stable catalytic features in subsequent cycles. The addition of tantalum allows obtaining a new catalyst with high efficiency of thiol species oxidation (higher than reported before for other catalysts). MPTMS modified TaMCF material appeared to be attractive for further study in different reactions requiring high concentration of acidic centres.