Synthesis of ordered mesoporous crystalline boron phosphate scaffold with double diamond surface structure

Abstract

Ordered mesoporous materials have received great attention due to their well-defined pore structures and potential applications in catalysis, adsorption, separation, drug delivery, etc. Although various compositions of mesoporous solids have been successfully prepared, the preparation of crystalline non-metallic oxyacid salts with ordered mesoporosity remains a major challenge. Herein, we report the synthesis of a mesoporous solid acid crystalline boron phosphate (BPO₄) catalyst with a bicontinuous shifted double diamond (SDD) hyperbolic surface structure. The BPO₄ scaffold was obtained by synergistic self-assembly in a mixed solvent of water and tetrahydrofuran using the diblock copolymer poly(ethylene oxide)-block-polystyrene as template and phosphoric acid and orthoboric acid as inorganic sources. The structure consists of two sets of diamond networks adjacent to each other with a mesostructural scale tetragonal symmetry (space group I4₁/amd) with unit cell parameters of a = 80 nm and c = 113 nm, which affords the scaffold a specific surface area of 44 m²/g. As a solid acid catalytic material, the SDD BPO₄ scaffold exhibited excellent catalytic activity at room temperature with a conversion of furfural to 2-(dimethoxymethyl) furan over 70% and can be reused after recovery without serious loss of activity. In the propane oxidative dehydrogenation reaction, SDD BPO₄ demonstrated high olefin productivity and selectivity while maintaining high reaction rate. This study provides ideas for the preparation of ordered mesoporous crystalline catalytic materials and demonstrates their potential for practical applications.