Formation of Selective Adsorption Cavity by Chemical Vapor Deposition of Molecular Sieving Silica Overlayer on Alumina using Molecular Template in the Presence of Acetic Acid

Abstract

Chemical vapor deposition (CVD) of tetramethoxysilane was carried out on alumina after the pre-adsorption of aldehyde as the molecular template, in order to form a molecular-sieving silica overlayer with controlled cavities. The adsorption of a molecule (1-naphthaldehyde) larger than the template was almost completely suppressed when acetic acid was added during CVD, showing a high selectivity based upon the shapes of the controlled cavity and the adsorbed molecule, while the selectivity was low when acetic acid was not used. The infrared (IR) spectrum and nuclear magnetic resonance (NMR) of 29Si showed that the acetic acid enhanced the oligomerization of Si alkoxide via hydrolysis, probably by acid catalysis, resulting in the formation of a dense network of siloxane. Such a dense wall of silica is speculated to determine the shape of the adsorption cavity precisely, and to generate high selectivity.

Molecular imprinting science and technology: a survey of the literature for the years 2004-2011

“…The development of alternatives to the synthesis of traditional monolithic polymers has been driven by both practical considerations, for example, ease of scale‐up, requirements for integration with other technologies, such as sensors, and for performance issues, for example, mass transfer or flow properties. Methods for preparation of discrete MIP particles, composites and molecularly imprinted polymer surfaces and fibers are areas that have been gaining in prominence over recent years and now constitute a significant portion of the original literature published in the molecular imprinting field …”

Supported Catalysts from Chemical Vapor Deposition and Related Techniques

“…The obtained SiO 2 /SnO 2 showed a chemisorption capacity and oxidation catalysis with specific selectivities probably based on the shapes of the cavities [89,90]. Aldehydes such as benzaldehyde adsorb strongly onto these basic surfaces.…”

Molecular-Imprinted Metal Complexes for the Design of Catalytic Structures

“…22.5). Silicate sources have been utilized to grow thin layers of SiO 2 onto oxide surfaces in a layer-by-layer fashion [85][86][87]. The Si(OCH 3 ) 4 precursor reacts with surface silanol groups preferentially, and polymerization does not occur in the absence of surface silanols.…”