TpyCo²⁺-Based Coordination Polymers by Water-Induced Gelling Trigged Efficient Oxygen Evolution Reaction

Though the use of conventional self-assembled architectures in functional applications involving advanced energy chemistries is an important research area, it remains largely unexplored. The self-assembly of the threefold and sixfold-symmetric terpyridines (tpy) with Co(II) salts results in a novel morphological and structural characteristics, regardless of the nature of the self-assembled fragments. Herein, such metallopolymers are achieved by one-pot synthesis in CH₃OH/CHCl₃ (v/v = 5:1) mixture ambient. It is found, for the first time, that Co-containing polymers can be well dispersed in deionized water to form gel-like self-assemblies that consist of a highly interconnected 3D network and exhibit enhanced electrical conductivity and thus are attractive as electrocatalysts. As expected, the optimized Co-based polymeric structures exhibit a low overpotential of 320 mV at 10 mA cm⁻² and high stability over 2000 cycles toward oxygen evolution reaction (OER), surpassing commercial RuO₂/C, single-site Co catalysts, polymer, and metal–organic framework-based OER catalysts reported to date. X-ray absorption spectroscopy and density functional theory calculations reveal that the tpy-Co²⁺ (3N-Co or tpy-Co²⁺) configurations act as highly active sites. Importantly, this work demonstrates the functional application of the self-assembled metallopolymers as electrocatalysts for energy conversion.