State-of-the-Art Membrane Solutions for Direct Air Carbon Capture (DACC): An Overview on the Current Status and Future Directions

Most efforts for carbon dioxide (CO2) emission reduction are focused on sequestering CO2 from large point sources such as power plants and the process industries. However, a quarter of global CO2 emissions (nearly 8 billion tons) emanate from small-point sources such as agriculture, waste management, domestic sector, and land use. These sources are distributed over vast areas and individually so small that conventional capture processes cannot filter the CO2 out, yet they still require active decarbonization. A solution to this problem is to pull CO2 directly from the free air. The UK Parliament’s climate change committee suggests that direct air carbon capture (DACC) could remove 1 billion tons of CO2 globally. The same report raises concerns over the inflated costs of CO2 removal associated with DACC (£250–400/ton of CO2). Indeed, the highly diluted concentration of CO2 in air (0.04%) imposes a high energy penalty and increases processing costs. The current state-of-the-art DACC involves an adsorption process that uses an amine adsorbent to remove CO2 from the air. The literature review reveals very few investigations reported on membranes for DACC until recently. Theoretically, membrane-based CO2 removal presents several advantages over conventional sorbent methods, including higher energy efficiency and lower operational costs. This Review summarizes recent advancements in membrane-based CO2 capture, focusing on innovations in structure and materials for improved direct air carbon capture (m-DACC). In addition, it systematically links membrane performance metrics with economic feasibility and scalability, providing a comparative framework for assessing industrial potential. Furthermore, it explores emerging trends in m-DACC applications, identifying key process optimizations and challenges that influence large-scale deployment. By synthesizing recent breakthroughs, this Review serves as a comprehensive guide for researchers and industry stakeholders seeking to advance the field of m-DACC.