Microwave-driven transformation of CO₂ adsorbents regeneration: A comprehensive review from principles to system designs

Conventional temperature-swing adsorption (TSA) for CO₂ capture is energy intensive, typically requiring more than 3.5 MJ/kg CO₂. Microwave-assisted regeneration technology has emerged as a promising alternative strategy due to the unique volumetric heating and selective heating advantages of microwave heating. This review provides a comprehensive analysis of the mechanisms and applications of microwave-enhancedregeneration of CO₂ adsorbents. First, the fundamental principles of microwave-induced TSA process intensification are elucidated by establishing correlations between the dielectric loss factor ε″ of CO₂ adsorbents and key performance metrics, including regeneration energy demand and desorption rate, thereby highlighting the role of microwave-induced hotspots. Following this, the review summarizes the design principles and synthesis strategies from diverse fields for engineering microwave-responsive adsorbents with tailored microwave-absorbing properties. Next, this review expands the scope to reactor-scale considerations and process integration, where the impact of system design, including impedance matching, cavity geometry, power feeding strategies, and gas-solid hydrodynamics, on overall energy utilization and temperature uniformity is examined. A comparative analysis of fixed-bed, fluidized-bed, and moving-bed configurations within microwave fields is presented, highlighting their respective synergies and operational constraints for scalable regeneration. Moreover, significant scientific and engineering challenges of microwave-assisted regeneration technology are reviewed, including insufficient fundamental understanding of quantitative relationships between hotspot intensity, desorption kinetics and long-term adsorbent deactivation, as well as scale-up problems associated with heating uniformity and limited microwave penetration depth. There remains a critical need to develop unified engineering guidelines by bridging advanced multiphysics modelling with practical reactor design, with the aim of achieving large scale and low energy CO₂ capture by establishing a competitive technological pathway.