Rational Design of Metal–Organic Framework Hybrids via Metal and Ligand Engineering for Enhanced Oxygen Evolution Reaction Catalysis

Despite significant progress in the development of metal–organic frameworks (MOFs) for oxygen evolution reaction (OER), most of the reported monometallic and monofunctional organic linker MOFs suffer from intrinsic limitations, including poor electrical conductivity, limited redox activity, and suboptimal exposure of catalytic active sites. To address these challenges, we integrated two structurally and chemically distinct MOFs: MIL-96 and ZIF-67. MIL-96 was synthesized using 1,3,5-benzenetricarboxylic acid (H3BTC) as the organic linker and aluminum as the metal center, providing chemical robustness. In contrast, ZIF-67 was fabricated by using 2-methylimidazole as the ligand with cobalt ions, contributing to enhanced electrical conductivity and abundant redox-active sites. By integrating these frameworks into a core–shell ZIF-67@MIL-96 hybrid structure, we aim to leverage their complementary properties to enhance the electrocatalytic performance. A comparative investigation of the individual MOFs (MIL-96 and ZIF-67) and their composites was carried out to evaluate their respective contributions to the OER activity. Electrochemical analysis reveals that the ZIF-67@MIL-96 hybrid exhibits a remarkable synergistic effect, achieving a significantly lower overpotential of 170 mV as compared with MIL-96 (190 mV) and ZIF-67 (230 mV). Furthermore, the hybrid displays the lowest onset potential of 1.28 V vs RHE, confirming its high electrocatalytic efficacy in an alkaline medium. This enhanced performance of ZIF-67@MIL-96 can be attributed to the coexistence of well-defined MIL-96 hexagonal crystals and polyhedral ZIF-67, with sharp edges, smooth surfaces, and distinct morphological features. This study highlights the effectiveness of combining distinct MOF architectures with different ligands and metal centers to overcome the limitations of conventional MOFs, offering a promising and cost-effective alternative to noble-metal-based OER electrocatalysts.