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

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)-NH 2- x (CH 3 ) 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)-NH 2 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)-NH 2 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.