Synergistic Regulation of Defect Density and Electronic Structure in Zr‐Metal‐Organic Frameworks via Selective Ligand Pyrolysis for Efficient Photocatalytic Biomass Conversion

Metal‐organic frameworks (MOFs) have emerged as promising photocatalysts for solar‐to‐chemical energy conversion owing to their well‐defined architectures, tunable porosity, and tailorable coordination environments. However, conventional MOF photocatalysts are predominantly employed as components in composite materials, and direct structural modulation of MOFs themselves to boost photocatalytic performance remains challenging. Herein, a ligand‐defective Zr‐MOF was synthesized via a selective ligand‐pyrolysis strategy and applied to photocatalytic conversion of liquid biomass into biodiesel. The generated ligand defects exposed additional coordinatively unsaturated metal sites, modulated the band structure, and reduced excessive electron localization within the framework. These defects also regulated the coordination environment of Zr 4+ sites, enhanced charge‐transfer efficiency, and acted as carrier‐trapping sites to suppress electron–hole recombination. Comprehensive characterizations reveal that H‐UiO‐66‐N‐0.3 possesses optimized frameworks and electronic structures favorable for substrate adsorption and charge separation. As a result, it achieved a biodiesel yield of 98.5% in the photocatalytic (trans)esterification reaction, with a rate constant 34 times higher than that of pristine UiO‐66. Collectively, this work realizes synergistic modulation of defect density, electronic structure, and catalytic activity via precise defect‐engineering, thereby providing a potentially viable design strategy to advance the application of MOFs in sustainable biomass transformation.