Defect-engineered MOF-808 for catalytic transfer hydrogenation of furfural: structural insights from comparative studies

Abstract

Acid–base sites are critical for catalytic transfer hydrogenation of furfural to furfuryl alcohol via the Meerwein–Ponndorf–Verley (MPV) reduction. Zirconium-based metal–organic frameworks contain abundant acid–base sites and show high activity in MPV reduction. Here, we report two distinct strategies to prepare defective MOF-808 (denoted as MOF-808-II_x and MOF-808-I_y) through partial substitution of tricarboxylate ligands with dicarboxylate or monocarboxylate ligands. Structural and physicochemical properties of the defective MOF-808 catalysts were systematically analyzed. Linker defects introduced additional acid–base sites at missing-linker nodes compared to pristine MOF-808, leading to significantly enhanced catalytic activity in MPV reduction of furfural. Furfural conversion increased from 72.9% (pristine MOF-808) to 85.3% (MOF-808-II₁₀) and 94.7% (MOF-808-I₄₀). The defective MOF-808 catalysts maintained activity over five consecutive cycles without significant deactivation, and a plausible reaction mechanism was proposed.