Thermal Chemisorption and Reduction of Carbon Dioxide on UiO-66(Zr) and MIL-100(Fe)

The continuous increase in global energy consumption has caused a considerable increase in CO₂ emissions and environmental problems. To address these challenges, adsorbents and catalytic materials that can effectively reduce the CO₂ levels in the atmosphere should be developed. Metal-organic frameworks (MOFs) have emerged as promising materials for CO₂ capture owing to their high surface areas and tunable structures. Herein, the CO₂ adsorption properties of MIL-100(Fe) and UiO-66(Zr) were investigated. Both MOFs exhibited excellent thermal stability and high CO₂ adsorption capacities at 300 K, and they maintained good adsorption properties at 500 K compared to those of activated carbon fiber owing to their high adsorption potentials. A slight change in the UiO-66(Zr) structure and no change in the MIL-100(Fe) structure were observed under the CO₂ atmosphere at 500 K. At that time, CO emissions and changes in the carboxyl and OCO functional groups were observed on MIL-100(Fe), suggesting a mechanism of CO₂ reduction to CO on the bare Fe(II) sites. These findings confirm the potential of MOFs for the thermo-catalytic reduction of CO₂ to achieve effective CO₂ capture and conversion.