Vanadium-Containing Mesoporous Silica of High Photocatalytic Activity and Stability Even in Water

Abstract

Vanadium-containing mesoporous silica molecular sieve (V proportional HMS) with tetrahedrally coordinated V-oxide species (VVO4) has been prepared by a modified surfactant-templating method, consisting of an addition of surfactant to a mixture of water, alcohol, and Si and V precursors followed by calcination. The V proportional HMS demonstrates high photocatalytic activity even in the presence of water, while other V proportional HMS's prepared by conventional templating methods and V/HMS prepared by an impregnation method show almost no activity owing to hydrolysis of the VVO4 species. ESR and photoluminescence measurements reveal that the modified templating method creates VVO4 species confined within a silica layer, while other methods create VVO4 species exposed on silica surface. The former VVO4 species are highly stabilized by the confinement within the silica, thus suppressing the hydrolysis. Another notable property of the confined VVO4 species is the higher photocatalytic activity even without water, despite their confined structure. This is explained by higher electrophilicity and longer lifetime of the excited-state VVO4 species (VIVO4*) derived from their distorted structure. The obtained findings suggest potential use of the modified surfactant-templating method for synthesis of stable and recyclable V-containing mesoporous silica with high photocatalytic activity.

A Fluorescent Molecular Switch Driven by the Input Sequence of Metal Cations: An Azamacrocyclic Ligand Containing Bipolar Anthracene Fragments

“…The salt was recrystallized in diethyl ether/ ethanol, affording L as a brown powder (0.45 g, 20 % Analysis: Steady-state fluorescence spectra were measured on a Hitachi F-4500 fluorescence spectrophotometer. [25] Absorption spectra were measured on a UV/Vis photodiode-array spectrophotometer (Shimadzu; Multispec-1500). [26] Time-resolved fluorescence decay measurements were performed by time-correlated single photon counting on a PTI-3000 apparatus (Photon Technology International) by using a Xe nanoflash lamp filled with N 2 as excitation source.…”

Titanium Oxide-based Photocatalysts for Selective Organic Transformations

“…Sequential reaction of 1,2,4-trihydroxybenzene on the catalysts, therefore, scarcely occurs and results in high selectivity. These photocatalytic systems en- , V 34) , and Cr _ O _ Ti bimetallic species 35) are also effective for selective organic transformations. In particular, Cr oxide species are very effective for partial oxidation of cyclohexane.…”

Structural and catalytic properties of V-SBA-15 for the vapor phase oxidation of diphenylmethane

“…The spectra were recorded between 190 and 800 nm on a Shimadzu UV-Vis spectrophotometer (model 2450) using BaSO 4 as the reference. 29 Si MAS NMR has been extensively used for the characterization of M41S silicate. Bruker DSX 300 spectrometer was used for MAS-NMR.…”

“…In addition to the above, the direct information about the oxidation state and coordination environment of vanadia species could be obtained from the color of the The 29 Si Magic angle spinning NMR is a powerful tool for the characterization of various mesoporous molecular sieves, allowing the detection of the heteroatom incorporated in the silicon framework position. 29 Si MAS NMR results of calcined V-SBA-15 catalysts are shown in Online Resource 1 ( Supplementary Fig.…”