A metal-assisted templating route (S0M+I−) for fabricating thin-layer CoO covered on the channel of nanospherical-HMS with improved catalytic properties

Abstract

Nanospherical hexagonal mesoporous silica (HMS) with a functional mesochannel covered with thin-layer-dispersed cobalt oxide species was directly fabricated via a novel metal-assisted templating method (S⁰M⁺I⁻). In this special method, cobalt ions would be enriched on the surface of the pore wall by physicochemical interactions among the surfactant, cobalt ions and silica. Typically, a metallomicelle template (S⁰M⁺) formed from the coordinative assembly of metal cations (Co²⁺, M⁺) with neutral surfactant dodecyl amine (DDA, S⁰) would match with negatively charged silicate oligomers (I⁻) by counter-ion interactions to assemble into the Co-modified HMS nanosphere. The metallization of DDA micelles and the role of cobalt ions in the assembly process can be demonstrated. Interestingly, the addition of amounts of cobalt apparently affects the size of the HMS nanosphere. Additionally, the coverage of CoO species on the mesochannel is increased with cobalt ions coordinated on the micelles. Finally, the functional Co-HMS with dispersed catalytic active phase and improved structure exhibits a special catalytic activity (yield of ca. 65%) for direct oxidation of phenol to p-benzoquinone with the assistance of a sulfate radical stimulated from cobalt in the presence of peroxymonosulfate.