Ultra-large Mesopores Research Articles

Facile Preparation of Ultra-Large Pore Mesoporous Silica Nanoparticles and Their Application to the Encapsulation of Large Guest Molecules

Pore-enlarged mesoporous silica nanoparticles (MSNs) were prepared directly from as-prepared MSNs through a new, simple method using divalent Ca or Mg salts as both efficient silica etching reagents and as ion exchangers in methanolic solution under mild conditions. The resultant MSNs became almost template-free simultaneously during this etching process. The pore-enlarged MSNs, referred to as Ca-MSN or Mg-MSN, maintained their original hexagonal pore symmetry and particle sizes, but several ultra-large mesopores were generated inside and outside the MSNs together with regular mesopores having expanded pore dimension of around 4-5 nm. The average pore diameters for ultra-large pores were 47.5 nm for Ca-MSN and 52.4 nm for Mg-MSN. The generation of ultra-large pores can be regarded as the collapse of several mesopores into an ultra-large pore. Both Ca-MSN and Mg-MSN were good sorbents for positively charged porphyrin molecules. Additionally, these ultra-large pore MSNs exhibited better adsorption ability than calcined MSN for large proteins and antibodies, such as bovine serum albumin (BSA) and immunoglobulin G (IgG).

High temperature and water-based evaporation-induced self-assembly approach for facile and rapid synthesis of nanocrystalline mesoporous TiO2

Through a high-temperature and water-based EISA (HW-EISA) approach, mesoporous TiO2 with high surface areas, ultra-large mesopores/pore volumes and tuneable bi-crystallinity (anatase plus rutile) can be facilely prepared in a ternary templating system (peroxotitanic acid/P123/H2O).

Mesocellular silica foam supported Ni2P catalysts with high hydrogenation activity

A series of nickel phosphide (Ni2P) catalysts supported on Y zeolite, SBA-15 and mesocellular silica foams (MCF) were prepared by the thermal treatment of nickel chloride and sodium hypophosphite at low temperature. The catalysts were characterized by XRD, nitrogen adsorption–desorption and TEM, and evaluated in the hydrogenation of cyclohexene. The supported Ni2P catalysts exhibited an obvious difference in catalytic performances. Ni2P/MCF was demonstrated to be highly efficient among three kinds of catalysts because the ultra-large mesopores and large pore volume of MCF promote the dispersion of Ni2P and accelerate the diffusion of reactant and product. Under the reaction conditions of 80 °C and 1.5 MPa, 40 % Ni2P/MCF afforded a very high cyclohexene conversion of 97.5 %.

Phenolic resin-based carbons with ultra-large mesopores prepared in the presence of poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide) triblock copolymer and trimethyl benzene

The evaporation-induced self assembly (EISA) strategy has been successfully employed to obtain ultra-large mesoporous carbons (UMC) by using Vorasurf 504 poly(ethylene oxide)–poly(butylene oxide)–poly(ethylene oxide), (PEO–PBO–PEO) triblock copolymer as a template. Resorcinol and formaldehyde were used as carbon precursors, whereas trimethyl benzene (TMB) was used as a pore expander. Nitrogen adsorption isotherms revealed that the resulting UMC materials possess ultra-large mesopores (about 27nm) and relatively narrow pore size distribution. Mesoporous carbons synthesized without TMB show also fairly large mesopores (about 20nm). These carbons were examined for adsorption of Lysozyme (Lz) from buffered solution at pH 10.8. All Lz adsorption isotherms were reasonably well fitted by Langmuir equation, giving high maximum adsorption capacity (31μmol/g).

Efficient CO2 sorbents based on silica foam with ultra-large mesopores

A series of high-capacity, amine impregnated sorbents based on a cost-effective silica foam with ultra-large mesopores is reported. The sorbents exhibit fast CO2 capture kinetics, high adsorption capacity (of up to 5.8 mmol g−1 under 1 atm of dry CO2), as well as good stability over multiple adsorption–desorption cycles. A simple theoretical analysis is provided relating the support structure to sorbent performance.

Synthesis of Highly Efficient WO<sub>3</sub>-Doped MCF Catalyst and Its Application in the Selective Oxidation of Cyclopentene to Glutaraldehyde

Synthesis of Highly Efficient WO<sub>3</sub>-Doped MCF Catalyst and Its Application in the Selective Oxidation of Cyclopentene to Glutaraldehyde

Adsorption of CO2 on mesocellular siliceous foam iteratively functionalized with dendrimers

Melamine-type dendrimers are grafted to mesocellular siliceous foam (MCF) with ultralarge mesopores by stepwise alternating treatments of the substrate with 2,4,6-trichlorotriazine and ethylenediamine. MCF grafted dendrimers up to 4th generation are prepared and characterized. Very high organic loadings (55 wt% at the 4th generation) are achieved, with half of the initial substrate mesopores volume remaining unoccupied—leaving room for the rapid ingress and egress of small gas molecules. The product materials possess relatively high thermal stability—their decomposition starts at around 300 °C. Adsorption measurements suggest that only the primary amine groups of these melamine type structures are active for CO2 chemisorption. The CO2 adsorption capacities of these adsorbents are improved relative to the unfunctionalized MCF, especially when considered on a wt% substrate basis.

Ethenylene-bridged periodic mesoporous organosilicas with ultra-large mesopores

E-configured ethenylene-bridged periodic mesoporous organosilicas with ultra-large mesopores and unprecedented pore volumes have been developed for the first time.

Synthesis and Catalytic Applications of Mesoporous Polymer Colloids in Olefin Hydrosilylation

AbstractMesoporous polymer particles (MPPs) have been synthesized by using the spherical microparticles of siliceous mesocellular foam (MCF) as a hard template. The MPPs possessed a robust structure with ultralarge mesopores, and a clean and inert surface. The surface properties of the MPPs could be tailored for various applications by using different functionalized monomers. An imidazolium‐pyrrolidine ligand was successfully immobilized onto MPPs and used as a supported platinum organometallic catalyst in olefin hydrosilylation. The MPP‐supported catalyst provided superior activity and selectivity for this reaction as compared to the MCF‐supported catalyst.

Fabrication and properties of silica monoliths with ultra large mesopores

Silica monoliths with ultra large mesopores of diameters over 25 nm and pore volumes in excess of 1.5 cm 3 g −1 were obtained by the hydrothermal treatment in aqueous ammonia solution of monolithic mesophases prepared by a direct templating of lyotropic liquid phase under high surfactant concentration. The process consists in the rearrangement of silica matrix structure from a template directed mesophase to that of a typical colloidal gel and is facilitated by template and silica extraction to the solution and basic conditions of the process. Silica of the monoliths hydrothermally treated in ammonia solution is somewhat less condensed than of untreated samples. The monoliths prepared using ethyl-silicate 40 as silica precursor posses slightly higher textural parameters than those synthesized using tetraethoxysilane. The size of pores depends on the concentration of ammonia in water solution and the time of treatment.

Structure and catalytic properties of vanadium oxide supported on mesocellulous silica foams (MCF) for the oxidative dehydrogenation of propane to propylene

A series of vanadium containing mesocellular silica foams (MCF) featuring a well-defined three-dimensional (3D) mesoporosity with ultralarge mesopores were studied with regard to their performance in the oxidative dehydrogenation (ODH) of propane. Catalysts supported on two-dimensional hexagonally ordered siliceous SBA-15 and MCM-41, as well as conventional amorphous silica, were also examined. The dispersity and the nature of the vanadium oxide species were characterized by means of DRIFTS, Raman spectroscopy, DR UV–vis, and H 2-TPR. Textural, SAXS, and TEM results indicate that the characteristic mesocellular structural features of MCFs are preserved after the vanadium incorporation. Spectroscopic measurements show that vanadium exists mainly in a tetrahedral environment in dehydrated V-MCF catalysts with V content <4.2 wt%, indicating that a very high surface concentration of isolated or low-polymeric VO x species could be achieved on the present V-MCF systems. The MCF-supported vanadia catalysts exhibit much higher propane conversion and propylene productivity than their conventional V-SBA, V-MCM, and V–SiO 2 counterparts in the ODH of propane, demonstrating that apart from the active redox sites, internal molecular transport in mesopores of the catalyst also plays an important role in the gas-phase selective oxidation reactions.

Continuous Fixed-Bed Gas-Phase Hydroformylation over PPh3-Modified Mesostructured Cellular Foam-Supported Rh Catalyst

siliceous mesostructured cellular foams (mcfs) are a new class of three-dimensional hydrothermally robust materials with ultralarge mesopores. the open system of large pores and the controllable pore size give mcfs unique advantages as catalyst supports. in this paper, mcfs were employed as supports in developing the pph3-rh/mcf catalyst for propylene hydroformylation in a fixed-bed reactor. the pph3-rh/mcf catalyst shows high activity (propylene conversion of 21.6% and butyraldehyde tof of 160.6 h(-1)), high selectivity (n-butyraldehyde/i-butyraldehyde = 10.4), and excellent stability under mild conditions of p = 1.0 mpa, t 393 k, and sv = 2 000 h(-1).

Fabrication of novel mesocellular carbon foams with uniform ultralarge mesopores.

Fabrication of novel mesocellular carbon foams with uniform ultralarge mesopores.

Microemulsion Templating of Siliceous Mesostructured Cellular Foams with Well-Defined Ultralarge Mesopores

Siliceous mesostructured cellular foams (MCFs) with well-defined ultralarge mesopores and hydrothermally robust frameworks are described. The MCFs are templated by oil-in-water microemulsions and are characterized by small-angle X-ray scattering, nitrogen sorption, transmission electron microscopy, scanning electron microscopy, thermogravimetry, and differential thermal analysis. The MCFs consist of uniform spherical cells measuring 24−42 nm in diameter, possess BET surface areas up to 1000 m2/g and porosities of 80−84%, and give, because of their pores with small size distributions, higher-order scattering peaks even in the absence of long-range order. Windows with diameters of 9−22 nm and narrow size distribution interconnect the cells. The pore size can be controlled by adjusting the amount of the organic swelling agent that is added and by varying the aging temperature. Adding ammonium fluoride selectively enlarges the windows by 50−80%. In addition, the windows can be enlarged by postsynthesis treatm...

Siliceous Mesostructured Cellular Foams with Uniformly Sized and Shaped Pores

ABSTRACTMesostructured siliceous cellular foams (mesocellular foams, MCFs) with homogeneous ultra-large mesopores are described. MCFs consist of uniform spherical cells 21–36 nm in diameter and possess surface areas up to 900 m2/g. Uniform windows, 7–18 nm in diameter, interconnect the cells to form a continuous 3-D pore system, which makes the MCFs attractive candidates for supports for catalysis and in separation and immobilization involving large molecules. They may be of interest in low-dielectric applications. The size of the cells can be controlled by the concentration of the added organic cosolvent. Adding small amounts of NH4F selectively enlarges the windows. We propose that the MCFs are templated by oil-inwater microemulsion droplets. The large-pore MCF materials resemble aerogels, with the benefit of a facilitated synthesis procedure in combination with well-defined pores and wall structure.