The growing anthropogenic CO 2 emission to the atmosphere over the past decades has raised a series of concerns over its environmental impacts, 1 such as global warming 2 and food security. Among the existing technologies to attack this problem, direct air capture (DAC) can effectively reduce the current amount of CO 2 already present in air and is specially suitable to remove distributed emission of CO 2 (from transportation vehicles, for example). DAC employs highly efficient sorbents to extract CO 2 from ultradilute sources (such as ambient air), and the extracted CO 2 can be further coupled with geological sequestration or conversion into value-added products. An increasingly popular class of DAC sorbents consists of amines supported into solid matrices. Supported amines composites can efficiently capture CO 2 from air at ambient conditions, are not adversely affected by water vapor and can be regenerated by relatively mild temperature swings. Since the amine chemical structure is known to influence both the CO 2 absorption capacity and the degradation of the supported amines, the development of new methods to understand CO 2 adsorption under experimentally-relevant condition is desirable. However, up-to-date, the mechanism of CO 2 binding in condensed phase amines at ambient conditions is still lacking.