Abstract:Deep eutectic solvents (DESs), distinguished by their low volatility, high thermal stability, structural tunability, and environmental friendliness, have emerged as highly promising novel absorbents for carbon dioxide capture. This review categorizes DESs into four types based on their interaction mechanisms with CO2 and systematically evaluates their capture performance and underlying principles: (1) Physical DESs achieve reversible adsorption through van der Waals forces and hydrogen bonding, resulting in low regeneration energy consumption, although they require high-pressure conditions. These types of DESs can be further integrated with porous supports or membrane technologies to construct high-performance material systems. (2) Amine-functionalized DESs enhance capture capacity at low partial pressures via chemical absorption; however, they are challenged by high viscosity. Strategies such as introducing hydrogen bond regulators, increasing steric hindrance, and modulating reaction product structures can be employed to design low-viscosity systems. (3) Superbase-derived DESs utilize guanidine/amidine superbases to activate hydrogen bond donor (HBD), thereby generating highly reactive anions for efficient capture. However, they pose potential toxicity risks, requiring simultaneous evaluation and regulation of biocompatibility to balance performance and safety during optimization. (4) Ionic liquid-type DESs combine the advantages of ionic liquids and DESs to reduce viscosity and improve absorption efficiency. Nevertheless, further optimization of the synthesis pathway and reduction of absorbent costs are still required. The study further elucidates the influence of DES molecular structure, environmental parameters, and water content on CO2 capture performance. Specifically, (1) From a structural perspective, the basicity of the HBA and HBD components, the synergy between HBA and HBD, alkyl chain length, side-chain structure, and the introduction of specific functional groups also play critical roles in the CO2 capture performance of DESs. (2) In terms of operational parameters, the CO2 absorption capacity generally increases with pressure under constant temperature and decreases with increasing temperature under constant pressure. However, exceptions to this trend exist. Therefore, specific absorption operating conditions should be determined by comprehensively considering the structural features, physicochemical properties, and absorption mechanisms of DESs. (3) Regarding water content, an optimal range exists within DESs, necessitating a balance among various physicochemical properties during the capture process. Finally, the key challenges associated with DESs, the potential solutions, and the future development directions are discussed. (1) CO2 capture mechanisms remain incompletely understood, thus necessitating the development of models that correlate DES structures with CO2 capture performance. (2) Process development is hindered by a lack of physicochemical data, requiring the creation of a comprehensive DES database. (3) Formulation design suffers from low efficiency, which may be enhanced using machine-learning-assisted methods leveraging key structural parameters of DESs; (4) Engineering risks require systematic evaluation. It is suggested that a multi-dimensional assessment framework be established and that hybrid technologies and process intensification strategies be explored. Close-