Ligand Conjugation‐Induced Microenvironment Modulation in Defective Metal‐Organic Framework Promotes Photocatalytic Hydrogen Evolution

Abstract Metal‐organic frameworks (MOFs) are widely employed in heterogeneous catalysis. Enhancing the catalytic performance of MOFs depends critically on precise structural design. Herein, a pyrrole (named as “Pyr”)‐functionalized UiO‐66 photocatalyst is synthesized, by sequentially defect engineering (via Zr‐site vacancy creation) and Clauson‐Kaas reaction‐mediated pyrrole functionalization. The resulting hierarchically porous (HP) MOF, HP‐UiO‐66‐NH 2 ‐Pyr, exhibits exceptional visible‐light‐driven photocatalytic hydrogen production activity, achieving a hydrogen production rate of 4831.7 µmol g −1 h −1 . This value is more than 10 times higher than that of pristine UiO‐66‐NH 2 (463.2 µmol g −1 h −1 ) and approximately three times higher than that of HP‐UiO‐66‐NH 2 (1736.5 µmol g −1 h −1 ). Combined carrier dynamics analysis and density functional theory (DFT) calculations clearly disclose that defect introduction and conjugation extension synergistically optimize the Zr‐O cluster microenvironment, reducing electron‐hole recombination and enhancing charge separation efficiency. This distinctive microenvironment modulation creates additional photogenerated electron transport channels, prolongs excited‐state lifetime and electron migration rates, and thus notably improves photocatalytic performance. Considering the widespread presence of ‐NH 2 chromophore groups in porous materials, this study establishes a new conjugation‐based modification strategy for precise microenvironmental regulation, ultimately enabling the rational design of high‐performance catalysts with significantly enhanced photocatalytic activity.