Electrochemical Synthesis of Metal-Organic Frameworks Based on Zinc(II) and Mixed Ligands Benzene-1,4-Dicarboxylate (BDC) and 4,4′-Bipyridine (Bpy) and its Preliminary Study on CO₂ Adsorption Capacities

Efficient and environmentally friendly synthesis methods for metal-organic frameworks (MOFs) have emerged as a compelling topic in the organometallic field. In this study, we successfully electro-synthesized a MOF based on mixed ligands, benzene-1,4-dicarboxylate (BDC) and 4,4′-bipyridine (Bpy), denoted as MOF-508b, and investigated its CO₂ adsorption capacity, comparing it with that of Zn-BDC and Zn-Bpy coordination polymers. Unlike the circular shapes of Zn-BDC and Zn-Bpy, MOF-508 adopts a three-dimensional structure upon binding with the pillar ligand, featuring mesoporous pore sizes. MOF-508b demonstrates superior stability at room temperature, exhibiting a thermal stability of 400 °C. The CO₂ capture potential of the materials was assessed under low-pressure conditions at room temperature. The pillared layer of MOF-508b results in the reduction of open metal sites, facilitating the binding of active CO₂ through coordination, thereby influencing its optimum CO₂ adsorption capacity (2.51 mmol g⁻¹), which was found to be lower than that of Zn-Bpy (3.83 mmol g⁻¹) and Zn-BDC (4.46 mmol g⁻¹). The adsorption mechanism on MOF-508b follows the Weber-Morris model, emphasizing diffusion within particles over direct attachment to the material surface.