An orange peel-derived zirconium-coordination polymer for highly efficient reductive upgradation of 5-hydroxymethylfurfural†

Abstract

Both the use of renewable natural sources to prepare catalytic materials and the Meerwein–Ponndorf–Verley (MPV) reduction of carbonyl compounds are very attractive topics in catalysis. Neohesperidin (NES) with rich oxygen-containing groups can bind to various metal ions. In this work, NES has been used as the ligand to coordinate Zr(IV) for the synthesis of a porous coordination polymer (Zr-NES). Various characterization studies demonstrated the formation of robust porous inorganic–organic frameworks and strong Lewis acid–base sites in Zr-NES. Due to the presence of coordinatively unsaturated Zr sites, Zr-NES had highly active Lewis acid sites, so it can efficiently catalyze the hydrogenation of 5-hydroxymethylfurfural (HMF) to prepare 2,5-bis-(hydroxymethyl)furan (BHMF). After 2 h at a mild temperature of 120 °C, a BHMF yield of 99.0% with turnover frequency (TOF) of 8.5 h⁻¹ could be obtained. This robust bifunctional acid–base Zr-NES was also demonstrated to be effective in one-step reductive etherification of 5-HMF to 5-[(1-methylethoxy)methyl]-2-furanmethanol (MEFA), a potential biomass-derived fuel additive, with 90% yield. Kinetic studies revealed that the activation energy for CTH of 5-HMF was 44.73 kJ mol⁻¹, accounting for the high reaction rate. Due to the strong interactions between Zr⁴⁺ and oxygen-containing groups, Zr-NES was highly stable and could be reused without a significant decline in activity.