Mesocellular Silica Foam Research Articles

Molecule‐level Design to Form Pocket Structures for Improving Amine Efficiency in CO2 Capture

AbstractSolid amine adsorbents represent a promising class of CO2 sorbents, but their amine efficiency is limited by the inaccessibility of peripheral amines. The surface of mesocellular silica foam (MCF) is functionalized with the mixture of short‐chain 3‐Glycidyloxypropyl) triethoxysilane (GPTES) and long‐chain Octadecyltrimethoxysilane (OTMS), forming pocket structures on the support surface, thereby exposing more amine sites and enhancing the amine efficiency of polyethylenimine (PEI). The resulting adsorbent demonstrates a high CO2 adsorption capacity (5.02 mmol g−1 at 50 °C, 10 vol.% CO2, and 50%RH), high amine efficiency (0.43 at the dry condition), outstanding cyclic stability (0.5% performance decline per cycle under the conditions of dry CO2 regeneration), and fast adsorption kinetics (15 min for adsorption saturation at 50 °C). First‐principles calculations and CO2 temperature‐programmed desorption (TPD) experiments demonstrate that the introduction of GPTES and OTMS is beneficial to decreasing adsorption energy and forming paired carbamic acid states and ammonium carbamate states.

Effective multi-biocatalyst system with reusable NADH for transformation of glycerol to value-added dihydroxyacetone

Glycerol-based biorefinery can be a highly profitable process by producing highly value-added products such as dihydroxyacetone via combined catalytic strategies. Here, two-enzyme system is adopted for the transformation of glycerol into highly valuable dihydroxyacetone as well as cofactor regeneration at the same time. Glycerol dehydrogenase (GDH) and alcohol dehydrogenase (ADH) are co-immobilized within magnetically separable and spherical mesocellular silica foam (Mag-S-MCF), to prepare NER-(GDH/ADH). In details, GDH and ADH are adsorbed into the mesopores of Mag-S-MCF, and further crosslinked within the mesopores of Mag-S-MCF. The resulting nanoscale enzyme reactors (NER) of crosslinked GDH and ADH molecules within the bottle-neck structured mesopores can effectively prevent larger sized crosslinked enzyme aggregates from being leached out of smaller mesopores, due to the bottle-neck mesopore structure of Mag-S-MCF, as well as stabilize the activity of GDH and ADH upon chemical crosslinking, effectively preventing the denaturation of enzyme molecules. More importantly, the proximity of GDH and ADH molecules within mesopores of NER improves the efficiency of cofactor-mediated dual-enzymatic reactions by relieving mass-transfer limitations and improving cofactor recycling in an effective way, expediting both glycerol oxidation and dihydroxyacetone generation at the same time. As a result, the DHA concentration of NER-(GDH/ADH) and the simple mixture of NER-GDH and NER-ADH were 410 μM and 336 μM, respectively. To the best of our knowledge, this report is the first demonstration of stabilized nanoscale multi-enzyme reactor system, equipped with efficient cofactor regeneration within confined mesopores, for efficient glycerol transformation to high-valued dihydroxyacetone.Graphical

Thermo and pH-responsive nanocarriers based on mesocellular silica foam and poly(N-vinylcaprolactam-co-methacrylic acid): Synthesis, characterization, and in vitro cytotoxicity assay

Smart hybrid nanocarriers were prepared by grafting poly(N-vinylcaprolactam-co-methacrylic acid) (poly(NVCL-co-MAA)) onto mesocellular silica foams (MCF silica) to evaluate them as controlled delivery systems of doxorubicin (DOX). The development of these nanocarriers began with the synthesis of MCF silica with interconnected porous structures and an average pore diameter of 27 nm. Then, free radical polymerization was used to graft the smart copolymer, and some parameters such as comonomer concentration and reaction time were studied. The DOX was loaded by immersion in an aqueous drug solution, while the in vitro release was investigated at different pHs (7.4, 5.8) and temperatures (25, 37 °C). In addition, the cytotoxicity of nanocarriers was investigated in vitro using the direct contact method with human breast cancer cells (SKBR3). In general, hybrid nanocarriers with copolymer graft percentages ranging from 30 to 60 % were obtained. On the other hand, at higher grafting of poly(NVCL-co-MAA) onto MCF silica, higher drug loading (up to 6.41 × 10−2 mg DOX/mg HN) was observed. Furthermore, in vitro DOX release results suggested that the nanocarriers released up to 52 % at 37 °C and a pH of 5.8. Finally, the in vitro cytotoxicity assay revealed that the DOX-loaded hybrid nanocarriers were cytotoxic to SKBR3 cells, indicating a controlled administration of DOX from the nanocarriers compared to free DOX. These results suggest that nanocarriers could have great potential for use as controlled delivery systems of anticancer drugs.

Single-step propane transformation on vanadium-supported catalyst revealed by operando DRS UV–vis study

The present study investigated the influence of silica support texture on the catalytic performance of VOx/silica catalysts in the selective oxidation of propane. Two- and three-dimensional mesoporous materials, SBA-15 and MCF, were synthesized using hydrothermal methods to create different pore structures. Vanadium (approximately 5 wt%) was incorporated into the silica matrices (MCF, SBA-15) and SiO2 (used as a reference system) through impregnation. The surface composition, valence state, and reducibility of the VOx species accommodated in VOx/silica catalysts were characterized using X-ray diffraction (XRD), diffuse reflectance ultraviolet–visible spectroscopy (UV–vis DRS), temperature-programmed reduction with hydrogen (H2-TPR), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR) techniques. The catalytic properties of the catalysts were evaluated in the propane selective oxidation conducted at 470 °C, utilizing a mixture of oxidants (N2O and O2). Propane oxidation resulted in propane conversion of 34 %, propene selectivity of 49 %, and propene oxide selectivity of 20 %, corresponding to space–time yield of propene reaching 37 gC3H6 kgcat−1·h−1and propene oxide equal to 20 gPO kgcat−1h−1. The textural properties of the support materials noticeably influenced the stability of the catalysts. The vanadium catalysts supported on three-dimensional mesocellular silica foams (MCF) demonstrated superior activity, achieving turnover frequency (TOF) values of 9.0 × 10−4 s−1 for propene and 6.67 × 10−4 s−1 for propene oxide (PO). The unique three-dimensional ultra-large pores of the MCF material facilitated the generation of significant amounts of propene oxide, along with propene, while minimizing the formation of CO, CO2, and other oxygen-bearing by-products. Operando UV–vis studies supported by two-dimensional correlation analysis (2D COS) were employed to explain the diversity in the catalytic performance of VOx/silica catalysts. It has been found that the oligomeric vanadium species are the active sites in propane oxidative dehydrogenation, whereas the monomeric forms participate in propene oxide formation. Moreover, the reduction of V5+ to V4+ and even V3+ was identified as a crucial step in the reaction.A reaction scheme has been proposed based on catalytic experiments and spectroscopic insights.

The electrochemical performances of high surface area mesocellular anatase TiO2 foam anode for lithium–ion battery

Porous anatase TiO2 with mesocellular foam structure (MCF−TiO2) was facilely prepared through hard-templating using mesocellular foam carbon (MCF−C), which had been prepared through hard-templating using mesocellular silica foam (MCF). During the dual hard-templating processes, the MCF−TiO2 well preserved the original three-dimensional (3D) mesocellular nanostructure of MCF. The wall of MCF−TiO2 was composed of very tiny anatase TiO2 nanocrystals (NCs). The TiO2 NCs were of less than 20 nm dimension. The surface area of MCF−TiO2 was 144 m2 g−1, and the MCF−TiO2 also contained large void spaces. The high surface area 3D nanostructured anatase MCF−TiO2 with large void spaces was ideal for Li+ transport and charge transfer reactions when MCF−TiO2 was applied to the anode material of the lithium–ion battery (LIB). Galvanostatic charge–discharge measurement and cyclic voltammetry confirmed that the MCF−TiO2 was an efficient anode material. The specific capacity after 50 cycles at a current rate of 0.1C reached 187 mAh g−1; it also showed stable recycling performances due to the robust high surface area 3D nanostructure.

Mesocellular Silica Foam as Immobilization Carrier for Production of Statin Precursors.

The employment of 2-deoxyribose-5-phosphate aldolase (DERA) stands as a prevalent biocatalytic route for synthesizing statin side chains. The main problem with this pathway is the low stability of the enzyme. In this study, mesocellular silica foam (MCF) with different pore sizes was used as a carrier for the covalent immobilization of DERA. Different functionalizing and activating agents were tested and kinetic modeling was subsequently performed. The use of succinic anhydride as an activating agent resulted in an enzyme hyperactivation of approx. 140%, and the stability almost doubled compared to that of the free enzyme. It was also shown that the pore size of MCF has a decisive influence on the stability of the DERA enzyme.

Injectable Mesocellular Foam Silica Microparticles with a Dual Role of Cell‐Recruiting Scaffolds and Intracellular Delivery Vehicles for Enhanced Cancer Vaccine

AbstractThe cancer vaccine is one of the potent cancer immunotherapies based on provoking antigen‐specific adaptive immune responses in patients. Activating host antigen‐presenting cells by delivering antigens and adjuvants is one of the most important requirements to enhance cancer vaccine efficacy. This study proposes an effective cancer vaccine platform based on injectable mesocellular foam (MCF) silica microparticles with a dual role capable of in situ recruitment of host dendritic cells (DCs) and intracellular delivery of antigens to the recruited DCs. Subcutaneously administrated MCF microparticles loaded with chemoattractant to DCs (GM‐CSF), antigenic protein (OVA), and TLR9 agonist (CpG‐ODN) lead to robust DC maturation and high antigen‐specific T cell responses. The cell recruitment, DC activation, and T cell responses of MCF‐based cancer vaccine are significantly higher than injectable mesoporous silica scaffold, of which role is mostly limited to the cell recruiting scaffold. These features of MCF lead to effective inhibition of tumor growth in prophylactic vaccine setting and lung metastatic cancer model, representing MCF enabling cell‐recruiting scaffold formation and intracellular delivery of antigen can be a promising material platform for an enhanced cancer vaccine.

Co-grafting of polyethyleneimine on mesocellular silica foam for highly efficient CO2 capture

Solid amine materials have emerged as a class of adsorbent with promising potential for CO2 capture from gas mixtures, such as biogas and flue gas. In this work, we developed a novel CO2 capture material via co-grafting of polyethyleneimine (PEI) on mesocellular silica foam (MCF), and (3-glycidyloxypropyl)triethoxysilane (GPTES) was first used as a bridging medium. In the fabrication procedure of MCF@G-35.6 %PEI, a simple impregration of PEI in MCF modified with epoxy groups was conducted. In this procedure, the co-grafting of PEI was realized in terms of a portion of PEI (21.3 wt%) was anchored on the pore surface of MCF via the epoxy/amine reaction and the rest of PEI (14.3 wt%) could be stably attached to the pore surface of MCF via its interaction with anchored PEI. After systematic evaluation, the MCF@G-35.6 %PEI exhibited a maximum CO2 adsorption capacity of 2.78 mmol/g at 50 °C and 50 %RH and fast adsorption kinetics with equilibrium time (break through from C/C0 = 5 % to 95 %) is 22.85 min. Meanwhile, outstanding CO2 adsorption capabilities within a wide temperature range of 30–90 °C and a large concentration range of 5–30 % vol. CO2 were obtained by the use of MCF@G-35.6 %PEI. More importantly, the MCF@G-35.6 %PEI also exhibited an excellent long-term stability over 50 consecutive cycles. CO2 adsorption kinetics of the sorbent was found to follow Avrami’s fractional order model and intraparticle diffusion model. Furthermore, temperature-programmed desorption was conducted to investigate the desorption kneitics and adsorption mechanism. All these findings demonstrate the great potential of MCF@G-35.6 %PEI for carbon capture and sequestration (CCS) technology.

Novel mesocellular silica foam supported poly(amidoxime-ethyleneimine) network for fast and highly efficient uranium extraction from seawater

According to the global vision of“carbon peak and carbon neutrality”, extracting uranium from natural seawater is regarded as a promising candidate for meeting nuclear fuel demand. Nevertheless, owing to the very low uranium concentration and complexity of natural seawater, the development of adsorbent materials for extracting uranium from seawater with satisfactory efficiencies remains a great challenge. In this work, we for the first time developed a novel mesocellular silica foam (MSF) supported hyperbranched poly(amidoxime-ethyleneimine) (PAO-PEI) network (MSF@PAO-PEI). After systematic evaluation, the MSF@PAO-PEI exhibited high adsorption capacity and excellent reusability, fast adsorption kinetics as well as good adsorption selectivity and affinity towards uranyl ions, simultaneously. Besides the obtained short equilibrium time of ∼ 20 h, the MSF@PAO-PEI achieved a remarkable adsorption capacity of 926.2 mg-U/g-Ads. for 100 mg/L of uranium water solution. Meanwhile, the MSF@PAO-PEI showed evident higher selectivity towards uranium (29.3 mg g−1) against vanadium (7.2 mg g−1) and other coexisting metal ions in simulated seawater. Moreover, excellent reusability of MSF@PAO-PEI in eight consecutive adsorption–desorption cycles was also observed. More importantly, satisfactory extraction efficiencies (90.6–92.9 %) for U-spiked real seawater was obtained in 48 h. Finally, a uranium adsorption capacity of 1.102 mg g−1 for coastal seawater in 20 days was obtained. All these findings demonstrate the relatively good potential of MSF@PAO-PEI for extracting uranium from real seawater.

Design and Evaluation of Pegylated Large 3D Pore Ferrisilicate as a Potential Insulin Protein Therapy to Treat Diabetic Mellitus.

An iron-based SBA-16 mesoporous silica (ferrisilicate) with a large surface area and three-dimensional (3D) pores is explored as a potential insulin delivery vehicle with improved encapsulation and loading efficiency. Fe was incorporated into a framework of ferrisilicate using the isomorphous substitution technique for direct synthesis. Fe3+ species were identified using diffuse reflectance spectroscopy. The large surface area (804 m2/g), cubic pores (3.2 nm) and insulin loading were characterized using XRD, BET surface area, FTIR and TEM analyses. For pH sensitivity, the ferrisilicate was wrapped with polyethylene glycol (MW = 400 Daltons) (PEG). For comparison, Fe (10 wt%) was impregnated on a Korea Advanced Institute of Science and Technology Number 6 (KIT-6) sieve and Mesocellular Silica Foam (MSU-F). Insulin loading was optimized, and its release mechanism was studied using the dialysis membrane technique (MWCO = 14,000 Da) at physiological pH = 7.4, 6.8 and 1.2. The kinetics of the drug's release was studied using different structured/insulin nanoformulations, including Santa Barbara Amorphous materials (SBA-15, SBA-16), MSU-F, ultra-large-pore FDU-12 (ULPFDU-12) and ferrisilicates. A different insulin adsorption times (0.08-1 h), insulin/ferrisilicate ratios (0.125-1.0) and drug release rates at different pH were examined using the Korsmeyer-Peppas model. The rate of drug release and the diffusion mechanisms were obtained based on the release constant (k) and release exponent (n). The cytotoxicity of the nanoformulation was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using human foreskin fibroblast (HFF-1) cells. A low cytotoxicity was observed for this nanoformulation starting at the highest concentrations used, namely, 400 and 800 μg. The hypoglycemic activity of insulin/ferrisilicate/PEG on acute administration in Wistar rats was studied using doses of 2, 5 and 10 mg/kg body weight. The developed facile ferrisilicate/PEG nanoformulation showed a high insulin encapsulation and loading capacity with pH-sensitive insulin release for potential delivery through the oral route.

Synthesis and properties of COK‐12 large‐pore mesocellular silica foam

AbstractLarge, ink‐bottle‐shaped pores in mesocellular foams (MCFs) are desired for various applications requiring enhanced mass transfer or the immobilization of larger compounds. Hence, the cylindrical pores of COK‐12, an ordered mesoporous silica structurally comparable to SBA‐15 but synthesized at room‐temperature at quasi‐neutral pH, are chemically swollen into ink‐bottle pores. Therefore, p‐xylene is used as a more sustainable swelling agent compared to popular alternatives. Its high boiling point allows for an additional thermal aging step to amplify the mesostructure enlargement without needing additional chemicals. For COK‐12, the MCFs obtained at room temperature reach an unprecedented plateau for the modal mesopore cell and window diameter of 19.9 and 5.5 nm, respectively, with an underlying broad pore size distribution and distorted hexagonal lattice up to 14.5 nm, involving hexagonal and spherical structures. The combined chemical and thermal swelling resulted in the selective enlargement of the window diameter to more than 200% and a slightly increased cell diameter, pore size distribution, and hexagonal lattice distortion in comparison to the room temperature synthesis. Such materials are thought to be promising alternatives to SBA‐15‐based MCFs, often utilizing toxic catalysts during synthesis. The presented results pave the way for enhanced adsorptive, catalytic, and drug delivery performances for COK‐12‐based materials.

A palladium(0)-threonine complex immobilized on the surface of magnetic mesocellular foam: an efficient, stable, and magnetically separable nanocatalyst for Suzuki, Stille, and Heck cross-coupling reactions.

In this study, a new palladium nanocatalyst was supported on l-threonine functionalized magnetic mesocellular silica foams (MMCF@Thr-Pd) and was characterized by FT-IR, XRD, BET, SEM, EDS, VSM, TGA, ICP-OES and elemental mapping techniques. The obtained MMCF@Thr-Pd performance can show excellent catalytic activity for Stille, Suzuki, and Heck coupling reactions, and the corresponding products were obtained with high yields. More importantly, the efficient and stable MMCF@Thr-Pd nanocatalyst was recovered by applying an external magnetic field and reused for at least five consecutive runs without a change in the catalytic activity.

Investigation of the performance of dual-layered omniphobic electrospun nanofibrous membranes for direct contact membrane distillation

Direct contact membrane distillation (DCMD) is a viable one-stop solution for sustainable seawater desalination and wastewater recovery. In this study, robust dual-layered omniphobic electrospun nanofibrous membranes (ENFMs) were fabricated with a re-entrant architecture and low surface free energy. This was achieved by incorporating hydrophobic mesocellular silica foam (MCF-5) into the top layer, followed by the surface functionalisation with 1 H, 1 H, 2 H, 2 H Perfluorodecyltriethoxysilane to improve the membrane anti-wetting and anti-fouling resistance. The dual-layered ENFMs exhibited a high porosity and a water contact angle ≃ of 143˚ and displayed an excellent vapour flux of ∼ 8.5 Lm−2h−1 and NaCl rejection > 99.99% when tested with synthetic seawater. The long-term desalination of natural seawater revealed that the normalised permeate flux was > 0.98 (NaCl rejection > 99.97%), and a simple water wash could recover the loss of membrane hydrophobicity and performance caused by the membrane scaling. The fabricated ENFMs displayed excellent permeate quality (< 1 ppm organic content and < 30 µS/cm) when evaluated with synthetic wastewater containing pharmaceutical compounds (acetaminophen, diclofenac sodium, ibuprofen and amoxicillin). The dual-layered membranes demonstrated outstanding anti-wetting ability when challenged with increasing concentration of cationic surfactant cetyltrimethylammonium bromide (CTAB 1.5 mM) in saline oily wastewater. The preliminary investigations revealed that these ENFMs hold great potential to be further investigated for enhanced water recovery.

Screen-Printed Microcantilevers Coated With Functionalized Mesocellular Foam Silica for Detection of Solvent Vapors

This work presents an application of mass-sensitive microcantilevers coated with a new alternative of sensitive materials that is hexamethyldisilazane functionalized mesocellular foam silica (HMDS-MCF-Si) for detection of solvent vapors. The microcantilevers (3 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times2$ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times0.1$ </tex-math></inline-formula> mm) based on a lead zirconate titanate (PZT) beam sandwiched by thin gold (Au) electrodes were fabricated by screen-printing. Mesocellular foam silica (MCF-Si) was synthesized and used as the sensitive material due to its high specific surface area and pore volume. This material was functionalized by hexamethyldisilazane (HMDS) to enhance hydrophobicity. By a small deposition of HMDS-MCF-Si, the obtained devices demonstrated longitudinal vibration mode with the quality factor of approximately 200 at ambient temperatures. Responsiveness of the microcantilever coated with HMDS-MCF-Si to each solvent vapor at room temperature was compared. The largest response was obtained from exposure to toluene vapor with the sensitivity of 0.85 ppm/ppmV (218 mHz/ppmV) and a limit of detection (LOD) of 28 ppmV. The sensitivity dropped by almost six times when exposed to the higher polar vapor of ethanol. Very low response to water vapor (0.05 ppm/ppmV) confirmed the hydrophobic behavior of HMDS-MCF-Si. Detectable performances under different vapors of our device can be utilized as a guide for developing sensitive materials and resonant microcantilever-based vapor sensors.

Impact of Cerium Oxide on the State and Hydrogenation Activity of Ruthenium Species Incorporated on Mesocellular Foam Silica.

Herein, the impact of cerium species loaded on mesoporous silica of MCF type on the state and catalytic activity of ruthenium species was studied. Up to 20 wt.% of cerium was incorporated on the silica surface, whereas the same 1 wt.% of Ru loading was applied. The samples prepared were examined by low temperature N2 adsorption/desorption, XRD, XRF, ICP-OES, XPS and H2 chemisorption. The catalytic activity of the materials obtained was investigated in the transformation of levulinic acid to γ-valerolactone. It was documented that the presence of Ce favored an increase in the dispersion of ruthenium species, which had a positive impact on the hydrogenation activity for up to 10 wt.% of Ce. Nevertheless, the highest cerium loading had a negative influence on the textural parameters of the support.

Heterogeneous enantioselective hydrogenation of an unsaturated carboxylic acid over Pd supported on amine-functionalized silica

The heterogeneous enantioselective hydrogenation of the CC bond of aliphatic α,β-unsaturated carboxylic acids is a key asymmetric catalytic reaction because of its application in the production of pharmaceuticals. In this study, we investigated the enantioselective hydrogenation of (E)-2-methyl-2-butenoic acid over cinchonidine-modified Pd catalysts. To improve the catalytic performance, a support material, mesocellular silica foam (MCF), was functionalized by grafting with primary amines. The use of the amine-functionalized MCF (NH2-MCF) support resulted in enhanced activity and enantioselectivity. The promoting effects originated from the increased electron density of the Pd nanoparticles and the selective blocking of low-coordinated Pd sites by the strong interaction of the amine groups with Pd nanoparticles. Promisingly, the Pd/NH2-MCF catalyst maintained its enantioselectivity over five successive cycles, thus demonstrating the reusability. Our results provide insights into the origin of the promoting effects of amine-functionalized supports and offer a strategy for improving supported catalysts for structure-sensitive reactions.

Amine functionalized mesocellular silica foam as highly efficient sorbents for CO2 capture

A series of amine-functionalized CO2 sorbents were synthesized by grafting mono- and tri-amine substituted trialkoxysilanes on mesocellular siliceous foam (MCF) via a facile wet grafting method. The effect of amine type, amine loading level, and porous structure of silica on the CO2 adsorption performance was investigated. MCF silica with a three-dimensional (3D) interconnected porous structure was found to be suitable for preparing amine-grafted sorbents. Tested at 25 °C and 0.15 bar of CO2, the mono- and tri-amine grafted MCFs exhibited a fast adsorption rate and excellent CO2 adsorption capacity of 1.71 mmol/g for mono-amine and 2.07 mmol/g for tri-amine, which was much higher than amine grafted PQ and SBA-15 with a 2D porous structure, and the amine grafted silica sorbents prepared in previous studies. The large pore volume and pore size coupled with superior interconnectivity of MCF enable more surface silanol groups available and accessible for amino silanes, leading to a high amine loading level and excellent amine dispersion on the silica surface, which enhances both the CO2 adsorption capacity and adsorption rate of the developed sorbents. Cyclic adsorption–desorption tests confirmed the excellent stability of the amine grafted MCF.

Bimetallic Cu–Ni Nanometal Supported over Mesocellular Silica Foam As a Novel Catalyst for One-Pot Synthesis of Benzimidazole in DMF As a Bifunctional Reagent

Bimetallic Cu–Ni Nanometal Supported over Mesocellular Silica Foam As a Novel Catalyst for One-Pot Synthesis of Benzimidazole in DMF As a Bifunctional Reagent

Copper Supported on Ceria Mesocellular Foam Silica as an Effective Catalyst for Reductive Condensation of Acetone to Methyl Isobutyl Ketone.

Copper-containing materials based on Ce- and Ca-Nb-mesocellular foam (MCF) silica supports are prepared, characterized and applied as catalysts for gas-phase reductive condensation of acetone to produce methyl isobutyl ketone (MIBK). The properties of the materials, the interaction of metal species, and their role in the catalytic process are examined by nitrogen physisorption, XRD, XPS, CO2 -TPD, H2 -TPR, and chemisorption of NO and pyridine combined with FTIR spectroscopy. A synergistic interaction of Cu2+ , Cu0 , and CeO2 species incorporated in the MCF support enable the Cu/Ce-MCF catalyst to yield 34 % of acetone conversion with over 90 % MIBK selectivity at 250 °C. Moreover, this high catalyst selectivity is maintained during operation for 24 h despite a decline in catalyst activity. The catalytic performance is superior to that of hydroxyapatite-supported Cu and similar previously reported Pd-containing catalysts.

Magnetic mesocellular foams with nickel complexes: as efficient and reusable nanocatalysts for the synthesis of symmetrical and asymmetrical diaryl chalcogenides.

In this work, magnetic mesocellular foam (M-MCF) silica nanoparticles were prepared via inserting magnetic nanoparticles into the pores of mesocellular foams, the inner surface of which was functionalized with a methionine–nickel complex (M-MCF@Met–Ni). The structure of the as-prepared nanocatalysts was studied by FT-IR spectroscopy, BET, TGA, VSM, SEM, HR-TEM, EDS, WDX, XRD, and ICP-OES techniques. Thereafter, this nanocatalyst was used as a new, effective, and magnetically reusable catalyst for C–S and C–Se bond formation under mild conditions. All corresponding products were prepared with good yields and appropriate turnover number (TON) and turnover frequency (TOF), which reveals the high activity of this magnetic nanocatalyst in both reactions. In addition, the recovery and hot filtration tests indicated that this catalyst could be simply separated from the reaction mixture using an outside magnet and reused five consecutive times without any significant loss of its catalyst activity or metal leaching.