Key factors influencing direct CO₂ capture from air

Excessive CO₂ emission into the atmosphere has caused serious climate change that draws global concerns. Direct air capture (DAC) plays a crucial role in reducing atmospheric CO₂ concentration and mitigating climate change. In this review, we summarize the latest advances and emerging opportunities in DAC through three key aspects. First, we introduce two different types of air contactors (adsorption- and absorption-based) and their functions, unveiling their critical roles in DAC. Second, we discuss a number of effective capture agents for DAC, including solid adsorbent materials and liquid absorbent solutions, with emphasis on the capture mechanism and efficiency. Third, we present three typical methods for CO₂ release and capture agent regeneration that match DAC effectively, including temperature swing, precipitation-phase separation, and electrolysis, focusing on the CO₂ release process and energy consumption. In the end, we provide insights into the existing challenges, potential solutions, and future directions for advancing DAC technologies.