Transition metal-based coordination polymers of bipyridyl-ethylene for sunlight-driven photocatalytic CO₂ reduction into CO

Herein, three transition metal-based coordination polymers (CoBpe, NiBpe, and CuBpe) were synthesized via solvothermal reactions by combining the organic ligand 1,2-di(4-pyridyl) ethylene (Bpe) with cobalt(II), nickel(II), and copper(II) ions, respectively. Single crystal X-ray diffraction (SCXRD) characterization revealed the isostructurality of the cobalt- and nickel-based compounds, which crystallize in a monoclinic system and form a 1D ladder topology with interpenetrated square grids, while the copper derivative forms a linear chain topology within a triclinic crystal system. These structural differences are attributed to variations in synthesis conditions and counter anions. The materials presented herein exhibit optical and photoelectrochemical properties highlighting their semiconductor characteristics. They were used as catalysts for CO₂ reduction to CO, in photocatalytic systems with [Ru(bpy)₃]Cl₂ as photosensitizer (PS) and triethanolamine (TEOA) as sacrificial electron donor (SED), under simulated solar irradiation. CoBpe achieved a CO production rate of 287 mmol g⁻¹ h⁻¹ (4-hour experiment) and 410 mmol g⁻¹ h⁻¹ (8-hour experiment), placing itself as a competitive candidate among similar systems.