pH-Regulated Aqueous Catalytic Hydrogenation of Biomass Carbohydrate Derivatives by Using Semisandwich Iridium Complexes

Graphical Get wet : Full conversion of biomass-derived furfural to furfuryl alcohol and levulinic acid to γ-valerolactone with high turnover frequencies are reached by pH-regulated aqueous catalytic hydrogenation. In addition, the one-pot aqueous reaction of furfural for the preparation of γ-valerolactone is achieved. Semisandwich Ir complexes [Cp*Ir-(di-OMe-bpy)(OH 2 )][SO 4 ] (di-OMe-bpy=4,4′-dimethoxyl-2,2′-bipyridine) and [Cp*Ir-(di-OH-bpy)(OH 2 )][SO 4 ] (di-OH-bpy=4,4′-dihydroxyl-2,2′-bipyridine) are excellent efficient catalysts for the aqueous hydrogenation reactions of biomass carbohydrate derivatives. We show that pH value plays an important role in the hydrogenation reaction. By adjusting the pH value of the solvent, we can improve the catalytic efficiency and control the product distribution. The turnover frequencies (TOF) of hydrogenation of furfural up to 13 877 h −1 and TOF of hydrogenation of levulinic acid up to 12 200 h −1 at 120 °C were achieved. Converting furfural into γ-valerolactone in one step is observed at strong acidic aqueous system, which makes it easy to achieve a distribution-controlled product by pH adjustment.