Tuning pore diameter of platelet SBA-15 materials with short mesochannels for enzyme adsorption

Abstract

A novel route for preparing highly ordered platelet SBA-15 materials with short mesochannels (ca. 200 nm) and large pore diameters up to 12 nm is reported for the first time. Appropriate quantities of Zr(IV) ions and trimethylbenzene (TMB) were added to the conventional SBA-15 synthesis solution to obtain platelet SBA-15 (SBA-15-p) materials with expanded pores. Based on the results of conventional characterization techniques and in situsmall-angle X-ray scattering experiments, the key step to obtain a well-ordered 2D hexagonal pore structure without vesicle contamination was the pre-hydrolysis of tetraethyl orthosilicate (TEOS) in the Zr(IV) containing synthesis solution for about 25 min before adding TMB as the pore swelling agent. The resultant SBA-15-p materials had high surface areas (∼800 m² g⁻¹), large pore volumes (∼1.2 cm³ g⁻¹) and short mesochannels (∼200 nm). More importantly, the mesopore diameters Φ_{a_BdB}, analyzed by a modified Broekhoff-de Boer method with the Frenkel-Halsey-Hill equation (BdB-FHH) on the nitrogen adsorption isotherms, could be finely tuned to 7–12 nm by varying the amount of swelling agent and the hydrothermal temperature. When adsorbing cytochrome c enzyme at pH 4–10, the short-channel SBA-15-p materials demonstrated higher adsorption capacities and adsorption rates compared to conventional fiber-like SBA-15 materials (SBA-15-f). Furthermore, the uptakes of cytochrome c enzyme per surface area increased significantly on the large pore materials.