Layered sql-type cobalt triazine-carboxylate MOF for enhanced pseudocapacitance and visible-light hydrogen evolution

Abstract

A cobalt metal–organic framework (Co-MOF), {[Co₃(Tci)₂(μ₂-H₂O)₂(H₂O)₄]·2H₂O}_n, constructed from tris(2-carboxyethyl)isocyanurate (Tci) ligands, was synthesized by a slow evaporation method and structurally characterized by single-crystal X-ray diffraction, revealing a layered architecture built from cobalt paddle-wheel units and multicarboxylate ligands. When employed as a binder-supported electrode on nickel foam, the Co-MOF exhibited dominant pseudocapacitive behavior in 1.0 M KOH, arising from reversible Co²⁺/Co³⁺ redox processes. It delivered a high specific capacitance of 278.28 F g⁻¹ from cyclic voltammetry and 396.49 F g⁻¹ at 0.5 A g⁻¹ from galvanostatic charge–discharge measurements, along with good rate capability and low internal resistance. Electrochemical impedance spectroscopy confirmed fast interfacial charge-transfer kinetics governed primarily by surface-controlled faradaic processes. Beyond energy storage, the Co-MOF demonstrated efficient visible-light-driven hydrogen evolution, achieving a hydrogen production rate of 6.03 mmol h⁻¹ g⁻¹ and a cumulative yield of 24.13 mmol g⁻¹. These results underscore the potential of triazine-linked cobalt MOFs as multifunctional materials for integrated supercapacitor and hydrogen production applications.