Molecular imprinting of bulk, microporous silica

Abstract

Molecular imprinting aims to create solid materials containing chemical functionalities that are spatially organized by covalent or non-covalent interactions with imprint (or template) molecules during the synthesis process. Subsequent removal of the imprint molecules leaves behind designed sites for the recognition of small molecules, making the material ideally suited for applications such as separations, chemical sensing and catalysis. Until now, the molecular imprinting of bulk polymers and polymer and silica surfaces has been reported, but the extension of these methods to a wider range of materials remains problematic. For example, the formation of substrate-specific cavities within bulk silica, while conceptually straightforward, has been difficult to accomplish experimentally. Here we describe the imprinting of bulk amorphous silicas with single aromatic rings carrying up to three 3-aminopropyltriethoxysilane side groups; this generates and occupies microporosity and attaches functional organic groups to the pore walls in a controlled fashion. The triethoxysilane part of the molecules' side groups is incorporated into the silica framework during sol-gel synthesis, and subsequent removal of the aromatic core creates a cavity with spatially organized aminopropyl groups covalently anchored to the pore walls. We find that the imprinted silicas act as shape-selective base catalysts. Our strategy can be extended to imprint other functional groups, which should give access to a wide range of functionalized materials.

Cooperative catalysis by silica-supported organic functional groups

“…Multiple-point covalent imprinting has been employed to form pairs or triplets of identical functional groups within a silica matrix. The catalysts reported by Katz and Davis 38 illustrate this approach. Different molecular templates were prepared incorporating carbamate-protected amine groups and triethoxysilyl groups.…”

A synthetic nanomaterial for virus recognition produced by surface imprinting

“…It is based on the formation of a supramolecular complex of organic monomers together with a template molecule before polymerization. This procedure enables the threedimensional positioning of the recognition units in the produced organic polymer 15,16 . Inorganic molecularly imprinted materials have also been developed.…”

“…Inorganic molecularly imprinted materials have also been developed. For instance, Katz and David 15 reported on the imprinting of bulk microporous silica. The originality of their approach lies on the choice of a building block that was used to occupy the micropores and to attach the functional groups to the walls of those pores.…”

Dummy molecularly imprinted mesoporous silicates for selective adsorption of 2-naphthol

“…Traditionally, molecular imprinted polymers (MIPs) are prepared in the form of bulk monoliths. Davis et al first reported the imprinting of bulk amorphous silica [1]. The major drawback associated with the imprinted material was the difficult diffusion of adsorbents to imprinted sites.…”