Electrochemical purification of a cobalt-catecholate framework to suppress non-radiative recombination boosts...

Photocatalytic CO₂ reduction represents a fundamental route for solar-to-fuel conversion, yet its efficiency is often limited by rapid non-radiative recombination of photogenerated charge carriers induced by intrinsic deep-level defects. While extrinsic modifications have been widely explored, the targeted elimination of intrinsic deep-level defects remains a challenge. Herein, we report an electrochemical purification strategy that fundamentally resolves this issue in a conductive cobalt catecholate framework (Co-CAT). Starting from a mixed-valence Co²⁺/Co³⁺-CAT precursor containing electrochemically unstable Co³⁺ oligomers, precise potential control enables their selective removal, yielding a structurally relaxed and highly pure Co²⁺-CAT framework. Beyond defect removal, integrated GCMC, MD, and DFT simulations reveal that this purification process restores a uniform charge distribution, thereby achieving a well-balanced electronic-adsorptive-kinetic synergy. Endowed with localized Co 3d orbitals, selective CO₂ capture, rapid mass transport, and suppressed competitive adsorption, the purified Co²⁺-CAT thus achieves markedly enhanced charge-transfer kinetics and reaction turnover. Consequently, the photocatalytic CO₂-to-CO conversion rate improves by ∼80% (48 mmol g^-1 h^-1), surpassing all reported MOF-based CO₂RR photocatalysis. This work establishes electrochemical purification as an effective strategy for enhancing intrinsic catalytic activity and proposes a simple materials design strategy to maximize photocatalytic performance through defect elimination and charge-distribution regulation.