Research progress in CO₂ capture and in situ methanation conversion technologies

In the context of global carbon neutrality, the efficient capture and utilization of carbon dioxide （CO₂） has become a key technological pathway for mitigating climate change. Conventional carbon capture, utilization and storage （CCUS） technologies still face significant challenges in terms of transportation costs, storage safety, and high energy consumption across the entire process. Integrating CO₂ capture with in situ methanation through a “capture-conversion” integrated process enables the direct production of methane, providing a promising route for the synergistic realization of CO₂ emission reduction and energy storage. This review systematically summarizes the fundamental principles, material systems, and performance characteristics of three major CO₂ capture technologies, namely absorption, membrane separation, and adsorption, with a particular focus on their coupling strategies and recent advances in in-situ methanation. Representative materials and process designs for absorption-methanation, membrane separation-methanation, and adsorption-methanation coupling systems are discussed, with further attention to the specific challenges of capture-methanation coupling under low-concentration CO₂ and direct air capture （DAC） conditions. The differences among these coupling routes in terms of energy consumption, conversion efficiency, stability, and applicable scenarios are comparatively analyzed. Finally, the key challenges faced by current coupled systems, including energy synergy, material stability, thermodynamic and kinetic matching, and hydrogen supply, are summarized, and future research directions are proposed, such as the development of low-energy-consumption materials, integration of diversified hydrogen sources, and expansion toward multi-scenario applications. This review aims to provide a reference for the engineering development and large-scale implementation of CO₂ capture and methanation coupling technologies.