Benign Synthesis of Metal-organic Framework (MIL-101-Cr) and Evaluation of Carbon-dioxide Adsorption Behaviour Employing Adsorption Isotherm Models

Background: In today's world, rising temperature due to global warming is caused by higher concentration of carbon dioxide (CO2) emissions in the atmosphere. Metal-Organic Framework (MOF) materials have the potential to be used in carbon dioxide capture and utilization technology. Objective: The purpose of this work is to prepare metal-organic framework materials by a benign synthesis method using water as the solvent, followed by the characterization and property evaluation for CO2 adsorption study. Methods: MIL-101-Cr metal-organic framework and its derivatives with alkali ion dopants were prepared by benign hydrothermal synthesis route, which were characterized by powder X-ray diffraction method. The adsorption isotherms of CO2 for MIL-101-Cr and its derivatives were studied to comprehend the influence of alkali dopants on CO2 sorption behaviour. The equilibrium uptakes of CO2 were further evaluated by fitting the isotherms with Langmuir, Toth and Dubinin - Astakohv adsorption models to determine the adsorption parameters. Results: The crystalline structural integrity of MIL-101-Cr is not affected by doping with alkali ions. The isosteric heat of CO2 adsorption is diminished with an increase in alkali dopant size, while the induced surface structural heterogeneity increases with increasing alkali dopant size. Conclusion: The equilibrium and thermodynamic parameters calculated from this study are useful for applications in carbon dioxide capture and utilization technology.