Metal-organic frameworks and their composites for carbon dioxide capture: Recent advances and challenges

The excessive carbon dioxide (CO2) emission has gained global concerns due to its potential effects on climate change, species extinction, and plant nutrition deterioration. Metal-organic frameworks (MOFs) featured with high specific surface area, large porosity, and excellent structure tailorability have attracted much attentions, and they have witnessed significant advancements in their design and implementation for CO2 adsorption. In this review, the synthesis strategies (e.g., solvothermal method, hydrothermal reaction method, solution precipitation method, microwave method, and sonochemical method) of developing MOFs and their composites are first introduced. Second, the recent progress in the fabrication of different types of MOFs composites (e.g., MOFs/carbon materials, MOFs/ionic liquids, MOFs/nanofibers, MOFs/aerogels, and MOFs/other materials) is summarized. Third, typical modification approaches including pore windows and pore size optimization, regulation of MOFs topology, introduction of open metal sites, functionalized ligands, increase of basicity, and enhancement of hydrophobicity of MOFs and their composites for the enhancement of CO2 adsorption are further highlighted. Finally, the challenges and some suggestions for the future development of MOFs and their composites-based CO2 adsorbents are summed up. It is expected that these useful insights will be helpful for the future development of related MOFs and their composites with excellent CO2 adsorption performances.