Covalent Organic Frameworks for Energy Conversions: Current Status, Challenges, and Perspectives

Energy conversion into clean fuels is critical to society's health benefits and sustainable future; thus, exploring materials to enable and facilitate energy conversions with reduced climate-related emissions is a central subject of science and technology. Covalent organic frameworks (COFs) are a class of polymers that enables predesign of both primary- and high-order structures and precise synthesis of long-range structures through one-pot polymerization. Progress over the past 15 years in chemistry has dramatically enhanced our capability of designing and synthesizing COFs and deepening our understanding to explore energy-converting functions that originate from their ordered skeletons and channels. In this minireview, we summarize general strategies for predesigning skeletons and channels and analyze the structural requirements for each type of energy conversion. We demonstrate synthetic approaches to develop energy conversion functions, that is, photocatalytic and electrocatalytic conversions. Further, we scrutinize energy conversion features by disclosing interplays of COFs with photons, holes, electrons, and molecules, highlighting the role of structural orderings in energy conversions. Finally, we have predicted the challenging issues in molecular design and synthesis, and thought of future directions toward advancement in this field, and show perspectives from aspects of chemistry, physics, and materials science, aimed at unveiling a full picture of energy conversions based on predesignable organic architectures.