Three novel coordination polymers as bifunctional materials for the photocatalytic degradation of dyes and the oxygen evolution reaction in alkaline solutions

Abstract

Herein, three new coordination polymers (CPs), namely {Ni (4,4′-abpt)(2,5-fdca)H₂O]_n (1), [Co(4,4′-abpt)(2,5-fdca)H₂O]_n (2) and [Co(4,4′-abpt)(1,3-abc)]_n (3) {4,4′-abpt = 3,5-di-4-pyridinyl-4H-1,2,4-triazol-4-amine, 2,5-fdca²⁻ (the fully deprotonated forms of 2,5-furandicarboxylic acid), 1,3-abc²⁻ (the fully deprotonated forms of 1,3-adamantanedicarboxylic acid)} were synthesized under solvothermal conditions and were characterized by elemental analysis, thermogravimetric analysis, powder X-ray diffraction, and single crystal X-ray diffraction (1 and 3) techniques. Structural analyses revealed that 1 is a two-dimensional structure with quadrilateral holes, while 3 is a two-dimensional rhombus network configuration with a binuclear metal center. Three as-prepared compounds exhibited efficient photocatalytic performance for the degradation of organic dyes of crystal violet (CV), methylene blue (MB), and rhodamine B (Rh-B) under UV irradiation, among which, 1 exhibited the best photocatalytic activity with a percentage degradation of more than 96% for the three dyes in 30 min. In addition, in the free radical capture experiment involving 3, it was found that both, the hydroxyl radical OH˙ and superoxide radical (˙O₂⁻) were involved in the degradation process of dyes, among which, the OH˙ radical is the main species to trigger the photocatalytic degradation experiment. Finally, the electrocatalytic performance of the catalysts was investigated in 1 M alkaline KOH solution, and the results showed that all three catalysts had certain electrocatalytic performance, and the catalytic performance of 1 was slightly better than that of 2 and 3. It exhibited a low overpotential of 367 mV at a current density of mA cm⁻².