Hydroxylation of organic ligand during the synthesis of Bi-based MOFs resulting in extended light absorption and enhanced photocatalytic activity

While various strategies, such as introducing n-π* transitions and expanding π-conjugated systems, have been proven to effectively enhance light harvesting for metal-organic frameworks (MOFs), their practical application is often hampered by ligand structure dependency—specifically, the requirement for complex ligand synthesis. To address this limitation, this work reports an in-situ ligand hydroxylation strategy during the synthesis of Bi-based MOFs. This approach not only broadens the light absorption range of the MOFs but also circumvents environmentally unfriendly synthetic conditions (e.g., high temperature or strong oxidants). This phenomenon is first observed in BDC-(OH) 2 containing two hydroxyl groups, which is transformed to BDC-(OH) 4 with four hydroxyl groups in the final MOF, denoted as Bi-BDC-(OH) 4 , as directly seen in the single crystal structure. Furthermore, the in-situ hydroxylation process is successfully extended to other ligands, including gallic acid (GA) and quercetin (QC), demonstrating its universality. Importantly, the hydroxylation also increases the charge separation efficiency of Bi-BDC-(OH) 4 . This work provides a novel and practical strategy to enhance light utilization and improve the photocatalytic efficiency of Bi-based MOFs.