Harnessing humidity for direct air capture: Moisture-swing sorbent design and mechanisms

Direct Air Capture (DAC) and Post-Combustion CO₂ capture (PCC) using liquid and solid amine sorbents, received enormous attention due to worsening weather and climate change. Enhancing the efficiency of CO₂ capture and removal technologies is crucial, with a primary focus on reducing the energy demand for continuous capture-release cycles. Low-energy CO₂ removal strategies offer promising durability and low operational costs, and a low levelized cost per ton of CO₂ removal is preferred for large-scale implementation. This review highlights low-energy CO₂ removal approaches, such as moisture/humidity swing sorbents. This discussion covers the influence of structural and molecular characteristics, the effect of counter anions on CO₂ removal efficiency and kinetics, the impact of different operational factors on performance, and the long-term stability of these materials. Continuous exploration and optimization of these materials and methods are vital for advancing the moisture swing method, contributing to global efforts to combat climate change and promoting environmental sustainability. Finally, recommendations are provided for the design of innovative materials.