Direct air capture: Advances in materials, processes, and engineering

Direct air capture (DAC) is one of the few viable negative-emission technologies capable of removing carbon dioxide directly from ambient air. Despite rapid advances, most DAC systems remain at early stages of technological readiness, with deployment largely limited to pilot or demonstration scales. Their widespread commercial application is primarily constrained by high capital expenditure (CAPEX) as well as elevated operational expenditure (OPEX) resulting from the energy-intensive regeneration of sorbents. This review critically evaluates key areas driving the advancement of DAC technology, focusing on the design of next-generation sorbents and the development of energy-efficient, cost-effective DAC processes. We summarize recent advances in DAC processes and materials, covering solid adsorbents (amine-functionalized sorbents, metal organic frameworks, covalent organic frameworks, porous carbons), liquid absorbents (alkaline and amine solutions, ionic liquids), and emerging electrochemical capture approaches. For each class, structural features, capture performance, benefits, and limitations are outlined. Regeneration strategies are reviewed, with emphasis on low-energy and efficient pathways, such as Joule heating and electrochemical regeneration. Finally, the major technical, economic, and engineering challenges hindering large-scale DAC deployment are discussed. Overall, this review underscores that overcoming current material, process, and economic barriers is crucial to unlock the full potential of DAC as an effective and scalable climate intervention strategy. • Advancements of direct air capture (DAC) technologies were evaluated. • DAC processes and materials covering adsorbents, absorbents, and electrochemical capture approaches were summarized. • Structural features, capture performance, benefits, and limitations are outlined. • Major technical, economic, and engineering challenges hindering large-scale DAC deployment are discussed.