Review on covalent organic frameworks and derivatives for electrochemical and photocatalytic CO2 reduction

With increasing potential for environmental volatility in the wake of increasing atmospheric pollutants, the need for sustainable approaches towards renewable energy and pollution reduction is ever-expanding. In recent years, research has geared towards utilizing carbon dioxide, which is seen as the largest threat of climate change, to produce various other useful chemicals while decreasing carbon dioxide levels. Considering this recent research, covalent organic frameworks (COFs) have jumped into the spotlight as promising and exciting new catalysts development to drive efforts towards easing climate change. As a relatively new class of materials, COFs are high surface area crystalline networks with a large degree of fine-tunable chemistry and the capability of metallic hybridization and functional group modifications. This review is a comprehensive and detailed discussion of the recent research accomplishments and goals of both photocatalytic and electrocatalytic carbon dioxide reduction using COFs as catalysts. Recent COF electrochemical catalysis is thoroughly discussed through different metal-based and pristine COFs along with the material design principles necessary to reduce carbon dioxide effectively and selectively. COF photocatalysis is discussed namely on the remarkable ability of irradiation-induced carbon dioxide reduction for pristine metal-free, metalated, and hybrid COFs along with the ability of photocoupled electrocatalytic reduction. Additionally, final conclusions on the state of COF research are provided along with future suggestions towards expanding and improving the investigation and application of COFs for CO2 reduction.