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

Semi-sandwich Ir complexes [Cp*Ir-(di-OMe-bpy)(OH2)][SO4] (di-OMe-bpy = 4,4'-dimethoxyl-2,2'-bipyridine) and [Cp*Ir-(di-OH-bpy)(OH2)][SO4] (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 pH value of solvent, we can improve the catalytic efficiency and control the product distribution. The turnover frequencies (TOF) of hydrogenation of furfural up to 13877 h-1 and TOF of hydrogenation of levulinic acid up to 12200h-1 at 120 oC. Converting furfural into GVL in one step is observed at strong acidic aqueous system, which makes it easy to achieve a product distribution-controlled by pH adjustment.