Preparation of novel silica structures using a library of carbohydrate gel assemblies as templates for sol–gel transcription

Abstract

Four sugar-based organogelators (1–4) were synthesized, and their gelation ability was evaluated in organic solvents and water. It was shown that they act as versatile gelators of various organic fluids, forming various superstructural aggregates. The xerogels showed a single- and lotus-type fiber structure or a spherical structure. The difference in these organogel supramolecular structures has successfully been transcribed into silica structures by sol–gel polycondensation of tetraethoxysilane (TEOS), resulting in single or multiple (lotus-shaped) hollow fiber structures with 5–10 nm inner diameters or a spherical structure with 700–1300 nm outer diameters. These results indicate that novel silica structures can be created by transcription of various superstructures formed in organogels through the hydrogen-bonding interaction. Nitrogen adsorption–desorption isotherms were measured by a BET method. The silica obtained from the α-glucose-based organogel 1, β-glucose-based organogel 2, α-galactose-based organogel 3 and α-mannose-based organogel 4 had BET surface areas of 450, 475, 650 and 670 m² g⁻¹, respectively. The Q⁴/Q³ ratios of these silicas were estimated by ²⁹Si MAS NMR spectroscopy. The Q⁴/Q³ ratios for the silica materials obtained from 1, 2, 3 and 4 were 3.00, 3.05, 4.87 and 5.25, respectively. This is a novel and successful example showing that a variety of new silica structures are created using a library of carbohydrate gel fibers as their templates.