Synthesis and Characterization of Cobalt and Nickel‐Based Coordination Polymers: Advanced Materials for Dye Degradation

ABSTRACT This study presents the synthesis, structural characterization, and photocatalytic evaluation of three polymeric complexes: [Co(L) 2 (phen)(H 2 O) 2 ] n ( 1 ), [Co(L) 2 (bip)(H 2 O) 2 ] n ( 2 ), and [Ni(L) 2 (bip)(H 2 O) 2 ] n ( 3 ). Single‐crystal X‐ray diffraction analysis revealed that all complexes exhibit distorted octahedral coordination geometries, with Co (II) and Ni (II) centers coordinated by L 2− , bipyridine/phenanthroline ligands, and water molecules. The three‐dimensional frameworks are stabilized by intramolecular hydrogen bonding, resulting in robust polymeric networks. Thermogravimetric analysis (TGA) demonstrated excellent thermal stability for the complexes, with decomposition observed at high temperatures in a nitrogen atmosphere. UV–visible spectroscopy revealed band gaps of 2.9, 2.8, and 3.2 eV for 1 , 2 , and 3 , respectively, highlighting their potential as photocatalysts. Photocatalytic experiments using Erythrosin B under optimized conditions (30 mg/L, pH = 7, 4 mg catalyst) revealed that 2 achieved a remarkable degradation efficiency of 92.5% under UV light and 90.8% under sunlight within 20 min. Trapping experiments confirmed that superoxide radicals were the dominant reactive species in the degradation process. This comprehensive investigation underscores the potential of these metal–organic complexes as efficient and environmentally friendly photocatalysts for dye degradation under various light sources.