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Porous materials have attracted considerable attention in materials science, chemistry and multidisciplinary areas of research due to their diverse structures, tailorable functionalities, large surface areas, remarkable optical transparency, confinement and shape selectivity effects. The precise architecture of porous photocatalytic materials has been extensively reported by the hybridization of semiconducting nanoparticles (NPs), light-responsive metal complexes and plasmonic metal NPs with silica-based micro-, meso- and macro-porous nanostructures. This review targets to cover state-of-the-art accomplishments in the surface engineering chemistry of zeolites, mesoporous silica, and metal-organic frameworks (MOFs) as excellent host materials for solar to chemical energy conversion and environmental remediation. The specific advantages and disadvantages of representative porous materials in photocatalysis have also been elaborated and summarized. Finally, key advances and prospects are presented to overcome the current challenges in photocatalysis and to inspire further studies in this rapidly evolving research field. [ABSTRACT FROM AUTHOR]

Ag nanoparticles (NPs) have gained great attention owing to their interesting plasmonic properties and efficient catalysis under visible-light irradiation. In this study, an Ag-based plasmonic catalyst supported on mesoporous silica with isolated and tetrahedrally coordinated single-site Ti-oxide moieties, namely, Ag/Ti-SBA-15, was designed with the purpose of utilizing the broad spectral range of solar energy. The Ti-SBA-15 support allows the deposition of small Ag NPs with a narrow size distribution. The chemical structure, morphology, and optical properties of the prepared catalyst were characterized by techniques such as UV/Vis, FT extended X-ray absorption fine structure, and X-ray photoelectron spectroscopy, field-emission SEM, TEM, and N2 physisorption studies. The catalytic activity of Ag/Ti-SBA-15 in hydrogen production from ammonia borane by hydrolysis was significantly enhanced in comparison with Ag/SBA-15 without Ti-oxide moieties and Ag/TiO2/SBA-15 involving agglomerated TiO2, both in the dark and under light irradiation. Improved electron transfer under light irradiation caused by the creation of heterojunctions between Ag NPs and Ti-oxide moieties explains the results obtained in the present study. [ABSTRACT FROM AUTHOR]

One-pot reaction involving Pd-catalyzed H2O2 production from H2 and O2 and Ti-catalyzed successive oxidation with H2O2 in a single reaction vessel is an alluring strategy for the synthesis of targeted chemicals in terms of sustainability and economic competitiveness. In this study, a yolk-shell nanostructured catalyst, consisting of Pd nanoparticles (NPs) with core diameter ca. 4.0 nm and a porous titanosilicate shell of ca. 15 nm thickness, was fabricated by using an oil-in-water (O/W) microemulsion-based interfacial self-assembly approach. Compared with prototype titanosilicate-supported Pd NP catalysts and core-shell structured analogues, the yolk-shell nanostructured catalyst exhibited superior catalytic efficiency in the one-pot oxidation reaction of sulfides with 83 % H2O2 utilization efficiency, because of the productive effect of the titanosilicate shell in limiting the diffusion of H2O2 generated in situ over the encapsulated Pd NPs and the efficient access of the H2O2 to the neighboring active Ti sites. This study provides promising avenues for the development of multifunctional nanostructured catalysts that are useful for one-pot reactions. [ABSTRACT FROM AUTHOR]

A novel and facile method to fabricate yolk-shell nanostructured photocatalysts consisting of TiO2 nanoparticles (NPs) as the core and spherical hollow silica as the shell was developed. In the fabrication, commercial TiO2 NPs were directly incorporated into hollow silica spheres by utilizing oil-in-water (O/W) microemulsions as a template, followed by heat treatment to create a void space between the TiO2 core and the silica shell region. The synthesized yolk-shell nanostructured TiO2@SiO2 acts as an efficient photocatalyst with both improved adsorption properties and photocatalytic efficiency, which far outperformed those of naked TiO2 owing to the ability of the porous silica shell to adsorb/enrich small organic reactants (acetaldehyde and 2-propanol) inside the void space and efficient transportation to the adjacent active TiO2 core. Comparative photocatalytic tests using a large organic molecule (conalbumin) revealed that the porous silica shell with an average pore diameter of 2.0 nm endowed this material with a molecular-sieving property, demonstrating its potential application in combination with organic support materials. [ABSTRACT FROM AUTHOR]

Levulinic acid is considered one of the most important biomass-derived chemicals owing to its potential as a versatile building block to synthesize valuable fuels and chemicals. Levulinate esters, such as methyl levulinate and ethyl levulinate obtained via esterification of levulinic acid with alcohols, can in particular be used as fuel additives and plasticizers, and thus have a potential to replace a significant amount of petroleum-derived chemical feedstocks. In this article, sulfated zirconosilicates having P6mm hexagonal mesoporous structure were applied as solid acid catalysts to the esterification of levulinic acid with ethanol to produce ethyl levulinate, and the influences of preparation conditions on the structural properties and catalytic performances were investigated. A distinct correlation was observed between the catalytic activity and the density of acid sites, showing that dispersibility of the acid sites and the associated accessibility of the organic reactants play an important role in determining the overall activity. Among the catalysts tested, sulfated Zr–SBA-15 with optimum Zr content (Si/Zr ratio of 10.7) was found to be the best catalyst, the activity of which was far superior to that of conventional sulfated ZrO 2 . In addition, direct conversion of cellulosic sugars (glucose and fructose) into levulinate esters was also examined. [ABSTRACT FROM AUTHOR]

In the past decades, various photocatalysts such as TiO2, transition-metal-oxide moieties within cavities and frameworks, or metal complexes have attracted considerable attention in light-excited catalytic processes. Owing to high surface areas, transparency to UV and visible light as well as easily modified surfaces, mesoporous silica-based materials have been widely used as excellent hosts for designing efficient photocatalytic systems under the background of environmental remediation and solar-energy utilization. This Minireview mainly focuses on the surface-chemistry engineering of TiO2/mesoporous silica photocatalytic systems and fabrication of binary oxides and nanocatalysts in mesoporous single-site-photocatalyst frameworks. Recently, metallic nanostructures with localized surface plasmon resonance (LSPR) have been widely studied in catalytic applications harvesting light irradiation. Accordingly, silver and gold nanostructures confined in mesoporous silica and their corresponding catalytic activity enhanced by the LSPR effect will be introduced. In addition, the integration of metal complexes within mesoporous silica materials for the construction of functional inorganic-organic supramolecular photocatalysts will be briefly described. [ABSTRACT FROM AUTHOR]

Candida antarctica lipase A was immobilized on spherical silica nanoparticles with oil-filled core and oil-induced mesoporous silica shell with different silica shell structures. The immobilization of enzymes was achieved by directly adding enzymes to the oil-in-water emulsion system under ambient synthesis conditions, and the silica shell structure was controlled by the addition of the cosolvent ethanol to the initial synthesis medium. Detailed structural analysis revealed the formation of oil-filled spherical silica nanoparticles with 3.4-4.2 nm mesopores randomly arranged in the silica shell; the thickness and pore characteristics of these pores markedly changed with the addition of ethanol. The retention of the enzyme activity during biocatalysis was significantly affected by the structural properties of the silica shells, and it was found that a thick and dense silica shell is essential to afford an active, recyclable, and stable biocatalyst. Furthermore, the oil encapsulated within the core cavity was found to play an important role in achieving a high catalytic efficiency. [ABSTRACT FROM AUTHOR]

Silica supported amine materials are promising compositions that can be used to effectively remove CO2 from large stationary sources, such as flue gas generated from coal-fired power plants (ca. 10 % CO2) and potentially from ambient air (ca. 400 ppm CO2). The CO2 adsorption characteristics of prototypical poly(ethyleneimine)-silica composite adsorbents can be significantly enhanced by altering the acid/base properties of the silica support by heteroatom incorporation into the silica matrix. In this study, an array of poly(ethyleneimine)-impregnated mesoporous silica SBA-15 materials containing heteroatoms (Al, Ti, Zr, and Ce) in their silica matrices are prepared and examined in adsorption experiments under conditions simulating flue gas (10 % CO2 in Ar) and ambient air (400 ppm CO2 in Ar) to assess the effects of heteroatom incorporation on the CO2 adsorption properties. The structure of the composite adsorbents, including local information concerning the state of the incorporated heteroatoms and the overall surface properties of the silicate supports, are investigated in detail to draw a relationship between the adsorbent structure and CO2 adsorption/desorption performance. The CO2 adsorption/desorption kinetics are assessed by thermogravimetric analysis and in situ FT-IR measurements. These combined results, coupled with data on adsorbent regenerability, demonstrate a stabilizing effect of the heteroatoms on the poly(ethyleneimine), enhancing adsorbent capacity, adsorption kinetics, regenerability, and stability of the supported aminopolymers over continued cycling. It is suggested that the CO2 adsorption performance of silica-aminopolymer composites may be further enhanced in the future by more precisely tuning the acid/base properties of the support. [ABSTRACT FROM AUTHOR]

The inside back cover of the journal "Chemistry: A European Journal" is presented.

Porous materials are outstanding catalysts in various reactions using confinement and shape selectivity effects. Unsurprisingly, extensive research has been conducted on zeolites, pillared clays, metal oxides, metal organic frameworks, and mesoporous materials. In particular, selective oxidation of hydrocarbons stands out an important class of reactions, but the ability to avoid over-oxidation remains a challenge. Thus, the present review highlights the latest findings on octahedral and tetrahedral catalytic materials in oxidation reactions, primarily focusing on types of reactive oxygen species and approaches to their investigation, on the incorporation of different heteroatoms (Ti, Sn) into silica matrices for catalytic purposes and corresponding types of reactions and on surface engineering and design of "single-site catalysts". In addition, composite catalysts for one-pot selective oxidation reactions are reviewed, providing examples from photochemistry including "single-site photocatalysis", electrocatalysis, and integration of metal complexes with functional solid materials. Ultimately, the end goal of this review is to discuss current state-of-the-art approaches that are being used in the area of selective catalytic oxidations with some novel porous materials. This includes methods that are being used to study mechanistic details as well as new catalysts and new substrates for such oxidations. [ABSTRACT FROM AUTHOR]

Review: 96 refs. [ABSTRACT FROM AUTHOR]

Abstract: Hydrophobic modification of single-site Ti-oxide moieties containing mesoporous silica (TiSBA-15) surfaces was performed by using triethoxyfluorosilane (TEFS) as a silylation reagent. The pore structure as well as the high surface area of TiSBA-15 was retained even after modification of these surfaces. TiSBA-15 modified with suitable amount of TEFS exhibited higher catalytic performance for the selective oxidation of cyclooctene to 1,2-epoxy cyclooctane using aqueous H2O2 as an oxidant than the unmodified TiSBA-15. The improvement of surface hydrophilic–hydrophobic properties of TiSBA-15 is quite effective for the enhancement of catalytic activity. [Copyright &y& Elsevier]