One-Pot Synthesis of 5-Hydroxymethylfurfural from Glucose by Brønsted Acid-Free Bifunctional Porous Coordination Polymers in Water

Abstract

Efficient synthesis of 5-hydroxymethylfurfural (HMF) using glucose (Glc) as a starting material represents an important process in biomass transformation. In this study, novel bifunctional porous coordination polymer (PCP) catalysts [PCP(Cr)-NH2–x(CH3)x; x = 0, 1, or 2] containing Lewis acidic and Lewis basic sites have been synthesized and utilized as solid-phase catalysts for HMF synthesis starting from a Glc-in-water system. PCP(Cr)-NH2 was found as the optimal catalyst, with an HMF yield of 65.9% and Glc conversion of 99.9% in a water/tetrahydrofuran (THF) system. Compared with PCP(Cr), amino groups in PCP(Cr)-NH2 catalysts play a vital role in Glc isomerization and subsequent dehydration–cyclization process to obtain the highly selective and effective fructose-to-HMF conversion. High yield and chemoselectivity are ascribed to concurrent extraction of HMF into the THF layer just upon its formation in water. The mechanism of Lewis acid–base synergistic catalysis was deduced by means of infrared spectroscopy, and catalysts could be reused after simple washing procedure with high reproducibility.