Ordered Mesoporous Polyoxometalate–Organosilica Frameworks as Efficient Photocatalysts of the Hydrogen Evolution Reaction

Abstract

Polyoxometalate clusters have been recently established as promising nanomaterials for photocatalytic water splitting. Here, the synthesis is reported of mesoporous polymers composed of a 3D porous network of lacunary [XM11O39]q− (XM11; X=P, Si; M=W, Mo) polyoxometalate units connected by ethano‐bridged silsesquioxane linkers through a block copolymer‐templated crosslinking polymerization of 1,2‐bis(triethoxysilyl)ethane in acidic solution. The resulting materials feature an ordered mesostructured ethane–silica (MES) framework that hosts a high density of accessible polyoxometalate clusters, which allows for efficient catalytic reactions. XM11/MES hybrid polymers have a relatively high activity for the hydrogen evolution reaction with remarkable cycle stability under UV/Vis light irradiation (λ>360 nm), without the need for co‐catalysts or additional photosensitizers. It is also shown that the photocatalytic efficiency of these materials arises from the nanoscale pore structure, high surface area and chemical manipulation of the electronic band structure of constituting heteropolyoxo clusters.

Direct Synthesis of Mesoporous Siliceous Phosphotungstic Acid and Its Superior Catalytic Activity on the Cyclohexylation of Phenol

“…From the wide-angle XRD pattern, it can be seen that all the materials with silica content up to 8.3 g show a highly crystalline structure with several well-resolved characteristic peaks after the ethanol washing and calcination process. These peaks can be indexed as (110), (220), (222), (400), and (332) and match well with the XRD pattern of K 3 PW 12 O 40 , demonstrating that the original Keggin structure of PTA is still retained in the final product . Noteworthy, the crystallinity of the final product is affected when the amount of the silica source in the synthesis mixture is increased.…”

“…These peaks can be indexed as (110), ( 220), ( 222), (400), and (332) and match well with the XRD pattern of K 3 PW 12 O 40 , 23 demonstrating that the original Keggin structure of PTA is still retained in the final product. 24 Noteworthy, the crystallinity of the final product is affected when the amount of the silica source in the synthesis mixture is increased. This is mainly due to the fact that the silica source interferes with the bonding between the Keggin structure and the KCl salt.…”

“…The stabilization of PTA and the surfactant removal have been performed via the low-temperature calcination (below 400 °C). 24 The prepared mPTA-Si exhibits a high specific surface area, a large pore size, and a high stability in polar solvent and uniform spherical morphology. The structural order and the surface properties have been controlled by varying the amount of PTA in the synthesis mixture.…”

“…In this study, we report on the direct synthesis of mesoporous siliceous PTA (denoted as mPTA-Si) nanospheres stabilized within silica framework via KCl through a simple self-assembly of the nonionic surfactant (Pluronic F127), the PTA, and the silica source, tetraethyl orthosilicate (TEOS), in a single step, without using any corrosive acid. The stabilization of PTA and the surfactant removal have been performed via the low-temperature calcination (below 400 °C) . The prepared mPTA-Si exhibits a high specific surface area, a large pore size, and a high stability in polar solvent and uniform spherical morphology.…”

Non-covalent polyhedral oligomeric silsesquioxane-polyoxometalates as inorganic–organic–inorganic hybrid materials for visible-light photocatalytic splitting of water

“…13,14 To overcome these drawbacks, solid supports such as mesoporous silica, zeolites and metal-organic frameworks have been used for dispersing or immobilizing POMs to create tunable porous heterogeneous catalysts with higher surface areas. [15][16][17][18][19][20] However, problems such as leaching of metal components and low accessibility of the catalytic active sites by hydrophobic reactants occur because of the hydro-philic nature of the inorganic components. The synthesis of inorganic-organic hybrid materials based on POMs has been developed by introducing an organic counterpart through covalent and non-covalent interactions.…”