Tin–chromium bimetallic metal–organic framework MIL-101 (Cr, Sn) as a catalyst for glucose conversion into HMF

Abstract

5-hydroxymethylfurfural (HMF) is considered a promising platform chemical, from which numerous chemicals can be produced. Hence, developing an efficient catalytic system to convert glucose into HMF has drawn considerable attention. In this study, a series of Lewis acidic Sn–Cr bimetallic metal–organic frameworks, MIL-101(Cr, Sn), with different Sn ion loading were synthesized hydrothermally using acetic acid as the mineralizer and water as the solvent. The resulting MIL-101(Cr, Sn) was systematically analyzed as a catalyst for the conversion of sugar to HMF. Moreover, the effects exerted by various reaction parameters on HMF yield and selectivity were investigated. With glucose as the substrate and 0.5-wt% H2SO4 as a catalyst, an 85.75% glucose conversion with 22.64% HMF yield and 26.41% selectivity was achieved. Meanwhile, these parameters were improved via addition of MIL-101(Cr, Sn)-0.1. That is, glucose conversion, HMF yield, and selectivity were increased to 86.36%, 60.75%, and 70.35%, respectively, when using MIL-101(Cr, Sn)-0.1 and H2SO4 as the catalyst under the same reaction conditions. The MIL-101(Cr, Sn) structure enabled high stability of the catalyst in aqueous solutions with different pH values, while improving its thermal stability. Moreover, the catalyst could be reused several times despite a slight reduction in its catalytic activity. The current results illustrate that MIL-101(Cr, Sn) is an excellent acid and sustainable catalyst for the production of HMF from fructose, glucose, and starch.