Knowledge Mapping of Direct Air Capture Technologies: Bibliometric Insights and Technological Evolution

Direct air capture (DAC) has attracted growing attention as a key CO2 removal technology for carbon neutrality, yet its knowledge structure and technological evolution remain fragmented. This study analyzed 1979 publications from 2000 to 2026 using DDA, VOSviewer, CiteSpace, and chronological milestone analysis. Research accelerated after 2021, with annual output reaching 460 publications in 2025. The United States (641 publications) and China (443) led national output, while the Georgia Institute of Technology (86) and Oak Ridge National Laboratory (75) led institutional output. MIT, Imperial College London, and ETH Zurich recorded higher average citations per publication. Seven themes were identified through keyword clustering and statistics, comprising five technological pathways, namely solid sorbent (894), liquid absorption (768), electrochemical (258), membrane separation (368), and low-temperature (142), together with two cross-cutting themes covering DAC performance (1165), techno-economic assessment/life-cycle assessment (243). Solid sorbent and liquid absorption remained dominant, electrochemical DAC developed rapidly, and membrane and low-temperature followed increasingly differentiated trajectories. Unlike previous bibliometric studies, this analysis integrates collaboration networks, data-driven theme identification, technological milestones, and quantitative TEA/LCA comparisons across all pathways. The resulting knowledge map links publication patterns with technological performance, economic feasibility, and life-cycle impacts, supporting research prioritization, technology development, deployment, and policy formulation.