Search

International audience; Silica-based micro-, meso-, macro-porous materials offer attractive routes for designing single-site photocatalysts, supporting semiconducting nanoparticles, anchoring light-responsive metal complexes, and encapsulating metal nanoparticles to drive photochemical reactions by taking advantage of their large surface area, controllable pore channels, remarkable transparency to UV/vis and tailorable physicochemical surface characteristics. This review mainly focuses on the fascinating photocatalytic properties of silica-supported Ti catalysts from single-site catalysts to nanoparticles, their surface-chemistry engineering, such as the hydrophobic modification and synthesis of thin films, and the fabrication of nanocatalysts including morphology controlled plasmonic nanostructures with localized surface plasmon resonance. The hybridization of visible-light responsive metal complexes with porous materials for the construction of functional inorganic–organic supramolecular photocatalysts is also included. In addition, the latest progress in the application of MOFs as excellent hosts for designing photocatalytic systems is described.

An oxidative enzyme, horseradish peroxidase (HRP), was immobilized on phosphorus- and/or calcium-modified MCM-41 mesoporous silicas with suitable pore diameters. Structural analyses by means of XRD and nitrogen adsorption confirmed that the P- and/or Ca-modified MCM-41 materials retained their structural quality even after the modification or the enzyme immobilization. Detailed studies of the adsorption behaviors and characterization using FT-IR spectroscopy and zeta potential measurements revealed that the P and Ca atoms attached on the silica surface provided increased uptake of HRP molecules, which is attributable to the more negatively charged surface or strong interatomic interactions between these atoms and the functional groups of the enzyme. In particular, P-modified MCM-41 showed an improved adsorption capacity in a short adsorption period and over a wide pH range without denaturation of the protein structure, in which the largest HRP adsorption capacity was 154 mg/g. Furthermore, HRP immobilized on P-modified MCM-41 showed higher enzymatic activity and reusability in the oxidation of 1,2-diaminobenzene in an organic solvent at a temperature of 37 °C than that immobilized on the parent MCM-41. This enhancement in enzymatic activity can be related to the structural integrity of loaded HRP molecules and the strong adsorption on the P-MCM-41 surface. This work thus demonstrates that mesoporous silica bearing P and/or Ca atoms can provide a surface environment suitable for enzyme immobilization.