Environmentally friendly synthesis and morphology engineering of mixed-metal MOF for outstanding CO₂ capture efficiency

Abstract

Fossil fuels are a major source of energy, but they significantly contribute to CO2 emissions, exacerbating climate change. In this study, a sustainable CO2 adsorbent based on Mixed-Metal MOF-74 was developed using cobalt (Co) and nickel (Ni), demonstrating superior adsorption performance. To address the environmental concerns associated with conventional synthesis methods that often rely on toxic solvents and salts, a green synthesis approach was employed, utilizing environmentally friendly solvents. The synthesized material, engineered to adopt a rod-like morphology, demonstrates an enhanced surface area-to-volume ratio, thereby providing a greater number of accessible active sites for CO2 molecules. Comprehensive characterization confirmed the porous nature of the material. Among the compositions tested, the CoNiMOF-74 (1:1) exhibited the highest CO2 adsorption capacity, reaching 7.55 mmol/g at 25 °C and 9.36 mmol/g at 5 °C, demonstrating a strong interaction with CO2 (isosteric heat of adsorption: 40.7 kJ/mol). The experimental data were well represented by established adsorption models, including the Hill isotherm and fractional-order kinetic models, with R2 values above 0.95 for all metal compositions. Under simulated flue gas conditions, the adsorbent displayed excellent selectivity for CO2 over N2 (selectivity values: 25–28). DFT calculations revealed significant interaction with CO2, with an adsorption energy of −0.25 eV, underscoring the potential of material for effective CO2 capture. The material also demonstrated robust stability over ten adsorption–desorption cycles, indicating its suitability for industrial applications in CO2 capture.

Group Members

William A. Goddard III

Charles and Mary Ferkel Professor