Bifunctionalized Mesoporous SBA-15: A New Heterogeneous Catalyst for the Facile Synthesis of 5-Hydroxymethylfurfural

Abstract

Bifunctional porous nanomaterials are very demanding in the context of heterogeneous catalysis. A highly ordered 2D-hexagonal bifunctionalized mesoporous SBA-15 type material MPBOS (mesoporous bifunctionalized organosilica) has been synthesized via a post synthetic route. The surface of the SBA-15 has been functionalized with (3-chloropropyl)triethoxysilane to obtain MPCOS (mesoporous chloro-substituted organosilica) material, which undergoes an SN2 substitution reaction of the surface a grafted chloro group with the amine group of organic ligand 5-aminoisophthalic acid, in the presence of potassium carbonate under refluxing conditions, offering the bifunctional material MPBOS. The bifunctionalized material with exceptionally high Brunauer–Emmett–Teller (BET) surface area of 652 m2 g–1 and average pore diameter of 9.4 nm has been characterized thoroughly with powder X-ray diffraction (PXRD), N2 sorption analysis, solid state 13C cross-polarization magic angle spinning nuclear magnetic resonance (CP MAS NMR) spectroscopy, Fourier transform infrared (FT-IR), and UV–vis spectroscopy, high-resolution transmission electron microscopy (HR-TEM), field emission scanning electron microscopy (FE-SEM), thermogravimetric differential thermal analysis (TG/DTA), NH3 temperature programmed desorption (NH3-TPD), and CHN analysis. The total acidity of this material has been determined from the NH3-TPD analysis, and this is estimated as 1.94 mmol g–1. The acidic and basic sites present in this bifunctionalized material have been explored in catalytic conversion of abundant carbohydrates to hydroxymethylfurfural (HMF) with the highest yield of 74 mol % from fructose in organic polar solvent dimethyl sulfoxide (DMSO) under microwave assisted heating conditions.