Advances in the Structural Design of Covalent Organic Frameworks for Direct Air Capture of CO ₂

The increasing concentration of atmospheric carbon dioxide (CO2) poses a severe threat to global climate security, prompting an urgent demand for efficient carbon removal technologies. Among various carbon capture strategies, direct air capture (DAC) stands out due to its ability to extract CO2 directly from ambient air, making it a critical component of negative emissions approaches. Covalent organic frameworks (COFs), as a class of crystalline and porous organic polymers with tunable structures and high thermal and chemical stability, have emerged as promising candidates for DAC applications. Their well-defined architectures enable precise control over pore size, topology, surface area, and functional group incorporation, all of which are key to achieving selective and efficient CO2 adsorption under low-concentration conditions. This review systematically summarizes recent advances in the structural design and functional regulation of COFs for DAC. We first introduce the evolution of COF structural dimensionality─from 2D to 3D frameworks─and their impact on porosity and mass transfer. Subsequently, we discuss various strategies for functionalizing COFs with active sites, such as amines, ionic groups, and metal centers, to enhance the CO2-binding affinity and moisture resistance. Computational approaches, including grand canonical Monte Carlo (GCMC) simulations, density functional theory (DFT), and machine learning (ML), are also reviewed as powerful tools to guide the rational design of COF-based DAC materials. Finally, we evaluate the performance of representative COFs in DAC applications and outline the current challenges and future directions toward scalable, energy-efficient, and cost-effective COF-DAC systems. This review aims to provide a comprehensive reference for advancing COF-based materials toward practical deployment in carbon capture technologies.