Phenanthroline‐Engineered Cyclophosphazene‐Based 1D and 2D Co(II) Coordination Architectures for Visible‐Light Photocatalysis: Insights Into Structure–Property Relationships

Abstract

Pnictogen‐rich cyclotriphosphazene‐based Co(II) coordination polymers (PCPs), (PCPs; PCP  =  phosphazene coordination polymer), namely PCP‐14 and PCP‐15 , were synthesized using multicarboxylic acids ( H 4 L1 and H 8 L1 ) and a phenanthroline (phen) co‐ligand under solvothermal conditions. Single‐crystal X‐ray diffraction analysis shows that PCP‐14 adopts a one‐dimensional (1D) chain structure, whereas PCP‐15 exhibits a two‐dimensional (2D) undulating layered framework. Both materials exhibit semiconductive behavior and show photocatalytic activity toward the degradation of organic dyes (MB, RhB, and MO) under visible‐light irradiation. PCP‐14 displays enhanced photocatalytic performance, which can be attributed to its lower bandgap and more efficient charge‐transfer properties. In contrast, PCP‐15 shows comparatively lower activity, consistent with its electronic structure. A clear relationship between crystal structure and photocatalytic performance is observed, where framework dimensionality and intermolecular interactions, including π − π stacking, likely facilitate charge transport and suppress recombination. Both materials retain a significant portion of their activity after multiple cycles, indicating reasonable stability. These findings demonstrate the potential of cyclotriphosphazene‐based coordination polymers as visible‐light‐responsive photocatalysts for dye degradation.