Molecular selective photocatalysis by TiO2/nanoporous silica core/shell particulates

The coating of TiO2 particles (P25) by a nanoporous silica layer was conducted to impart molecular recognitive photocatalytic ability. TiO2/nanoporous silica core/shell particles with varied pore diameters of the shell were synthesized by the reaction of P25 with an aqueous mixture of tetraethoxysilane and alkyltrimethylammonium chloride with varied alkyl chain lengths, followed by calcination. The TEM and nitrogen adsorption/desorption isotherms of the products showed that a nanoporous silica shell with a thickness of ca. 2 nm and controlled pore diameter (1.2, 1.6, and 2.7 nm) was deposited on the titania particle when surfactants with different alkyl chain lengths (C12, C16 and C22) were used. The water vapor adsorption/desorption isotherms of the core/shell particles revealed that a larger amount of water adsorbed on the core/shell particles when the pore diameter is larger. The 29Si MAS NMR spectra of the core/shell particles showed that the amount of surface silanol groups was independent of the water vapor adsorption capacity of the products. The possible molecular recognitive photocatalysis on the products was investigated under UV irradiation using two kinds of aqueous mixtures containing different organic compounds with varied sizes and functional groups: a 4-butylphenol, 4-hexylphenol, and 4-nonylphenol mixture and a 2-nitrophenol, 2-nitro-4-phenylphenol, and 4-nitro-2,6-diphenylphenol mixture. It was found that the core/shell particles exhibited selective adsorption-driven molecular recognitive photocatalytic decomposition of 4-nonylphenol and 2-nitrophenol in the two mixtures.

Adsorption-driven molecular recognitive photocatalytic decomposition of organic molecules in aqueous mixtures was achieved on TiO2/nanoporous silica core/shell particles with controlled pore diameters.Figure optionsDownload high-quality image (40 K)Download as PowerPoint slideResearch highlights
► Nanoporous silica coating to impart molecular selective photocatalytic ability to TiO2 particle.
► P25 core/nanoporous silica shell particles with different size and silanol density of the pores.
► The hybrid materials exhibit molecular recognitive adsorption and photocatalysis.