Morphology dependence of zeolitic imidazolate framework-67 nanoreactor for carbon dioxide reduction and hexavalent chromium immobilisation

Energy conversion and pollutant remediation are essential means of environmental protection. Zeolitic imidazolate framework-67 (ZIF-67) is an ideal catalyst for these processes. In this study, four morphologies of ZIF-67 were synthesised for the photocatalytic conversion of carbon dioxide (CO₂) and adsorption of hexavalent chromium (Cr(VI)). Under light irradiation, rhombic ZIF-67 (ZIF-R) converted carbon dioxide to carbon monoxide (CO) and methane (CH₄), with production rates of 1182.62 and 27.21 μmol g⁻¹ h⁻¹, respectively. Furthermore, comprehensive experiments were conducted to examine the effects of reaction duration, pH, starting concentration, coexisting ions and temperature, along with corresponding kinetic and thermodynamic analyses. Results demonstrated that ZIF-R exhibited outstanding Cr(VI) adsorption capacity (46.87 mg g⁻¹). After four cycles of adsorption and photocatalytic experiments, ZIF-R maintained excellent reusability. Thus, ZIF-R is an efficient photocatalyst and stable adsorbent, offering a promising solution for mitigating greenhouse gas emissions and removing environmental pollutants.