Recent advances on metal-organic frameworks (MOFs) and their applications in energy conversion devices: technical review

Metal-organic frameworks (MOFs) have enticed huge interest over the years in a wide range of applications, including electrochemical energy storage/conversion devices, due to their controllable porous structure, tuneable composition, excellent thermal/chemical stabilities, and facile synthesis. However, conductivity enhancement and synthesis of redox-active MOFs are two key challenges hindering their large-scale applications in electrochemistry. Redox-active MOFs can be prepared using redox-active ligands and metal ions, which in turn leads to an additional benefit of π-stacking interactions. Conductivity improvements through favourable overlap of energy and orientation of both metal and ligand, π-π stacking, and the incorporation of a guest molecule to induce free charge carriers and reduce band gaps are key strategies. This review provides a detailed assessment of various synthesis techniques followed by post-production treatments to improve MOF's conductivity. The use of MOFs and MOF-based nanomaterials in electrochemical devices, including batteries, supercapacitors, and fuel cells, as well as the progress in using MOF and MOF-based catalysts for CO2 reduction and as a photocatalyst for hydrogen production, have been scrutinized by highlighting their benefits and shortcomings. Finally, the challenges MOFs and MOF-based materials face and their prospects when adopted as active materials in energy storage/conversion devices, as well as CO2 reduction and green hydrogen production, have also been elaborated.