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

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.