Fabrication of ZC-bimetallic MOF derived ZCO/Co3O4 by different zinc source anions and the effect on photocatalytic performance

Abstract

The morphology and structure of photocatalysts play a critical role in determining their performance. Consequently, synthesizing nanomaterials with specific morphologies through simple, cost-effective, and controllable methods has emerged as a central research focus in the field of photocatalysis in recent years. In this study, we designed and synthesized ZnCo₂O₄/Co₃O₄ (ZCO/Co₃O₄) nanostructures with specific morphologies, controlled by altering the anion species (SO₄²⁻, NO₃⁻, Cl⁻, or CH₃COO⁻) in zinc precursor salts. This anion-regulated synthesis yielded four distinct ZCO/Co₃O₄ samples, designated as S-ZCO/Co₃O₄ (sulfate-derived), N-ZCO/Co₃O₄ (nitrate-derived), C-ZCO/Co₃O₄ (chloride-derived), and A-ZCO/Co₃O₄ (acetate-derived). The effect of different anions on the surface morphologies and photocatalytic activities of ZCO/Co₃O₄ samples was investigated by scanning electron microscopy (SEM) and photocatalytic degradation experiments. The results demonstrated that the anion species not only exerted a significant effect on the morphology of the ZCO/Co₃O₄ nanostructures but also significantly influenced their particle size and porosity. BET analysis revealed that C-ZCO/Co₃O₄ exhibited a significantly larger average pore size (52.5 nm) than other samples, while all samples demonstrated distinct degradation efficiencies for methyl orange (MO). The ZCO/Co₃O₄ sample synthesized using zinc chloride exhibited small, uniformly sized particles and demonstrated the best photocatalytic performance among the four samples, achieving a high degradation rate of 93.8% within 40 minutes. Pseudo-first-order kinetic analysis demonstrated that the C-ZCO/Co₃O₄ sample exhibited a rate constant (k = 0.0687 min⁻¹) approximately four times higher than those of the other samples (k_A-ZCO/Co3O4 = 0.0164 min⁻¹, k_N-ZCO/Co3O4 = 0.018 min⁻¹, k_S-ZCO/Co3O4 = 0.0182 min⁻¹). Finally, a possible degradation pathway for MO was proposed using LC–MS. In addition, the catalyst demonstrated broad applicability for degrading various organic dyes. This study proposes a novel strategy to synergistically control the morphology of transition bimetallic oxides through anion-regulated synthesis, improving the catalytic performance of the materials.