Reticular Synthesis of Covalent Organic Frameworks for Carbon Dioxide Adsorption

Comprehensive Summary The fast increase in atmospheric carbon dioxide (CO 2 ) concentration has become a pressing issue that requires immediate attention to mitigate the significant global warming and the associated environmental crisis. Although the ongoing development of renewable technologies provides long‐term solutions to reduce CO 2 emissions, the current global aim to cut emissions and reach near‐zero emissions by 2050 requires more effective complementary methods to achieve the goals. Sorbent‐based CO 2 capture offers a promising approach to realize massive carbon capture and storage due to its low cost. Central to the advantages of this method are porous solids, and an efficient capture process requires the materials to have high CO 2 capacity, fast kinetics, good selectivity, and long‐term stability under operating conditions. Guided by reticular chemistry, which enables the linking of molecular building blocks into crystalline frameworks through strong bonds, covalent organic frameworks (COFs) emerge as a new class of crystalline functional polymers and have demonstrated great potential as efficient CO 2 adsorbents due to their high porosity, tailor‐made pore environment, and excellent stability. The CO 2 uptake capacity of COF‐based sorbent exhibits a high value up to 6 mmol·g –1 at 273 K and 1 bar. Considering the impressive progress in this field, a timely review summarizing the past structural design strategies of COFs for CO 2 sorption and revealing the underlying structure‐function relationship can pave the way for developing the next‐generation COF‐based sorbents for practical CO 2 capture. This review provides the fundamental design principles of COFs and summarizes the recent de novo and post‐synthetic modification methods for designing suitable COFs toward CO 2 capture. The important role of the building units, the linkages, and the topologies of COFs that elucidate the basic structural properties of COFs during the formation of the crystalline frameworks and the CO 2 capture process is highlighted. Finally, the challenges and possible future development of this field are discussed. Key Scientists In 2009, Yaghi and co‐workers reported the first experimental study of CO 2 adsorption in COFs, opening the following works on applying COFs to CO 2 adsorption and advancing the development of this field over the past two decades. In 2015, Jiang and co‐workers developed several post‐synthetic modification methods to modify COFs toward CO 2 adsorption. The pore environment of COFs could be modified by the famous click reactions and the well‐developed ring‐opening reaction, thus enhancing the CO 2 capture performance of these COFs. In addition to post‐synthetic modification methods, Loh (2018), Lotsch (2019), and their co‐workers constructed several 2D COFs with unreacted functional groups for CO 2 adsorption through direct synthesis. Besides 2D COFs, Wang, Fang, and co‐workers designed a series of 3D COFs and applied them to CO 2 adsorption between 2016 and 2021. In 2023, Zhao and co‐workers reported a post‐synthetic modification method to modify the pore properties of COFs. They doped the COFs with metal salts and achieved an impressive enhancement of their CO 2 adsorption performance. In 2024, Yaghi and co‐workers reached a milestone by introducing the polyamine species into COFs. These new COF‐based CO 2 adsorbents could achieve direct CO 2 capture from the air with exceptional uptake capacity, high cyclic stability, and fast kinetics.