Water-Triggered Direct Air Capture by Strong Organic Bases

Abstract

A key challenge for sorbent-mediated temperature-swing direct air capture remains to maximize the difference in CO₂ loading under capture and regeneration conditions (i. e. the working capacity) while minimizing the thermal energy input required to alternate between the two equilibrium states. Herein, peralkylated guanidines were shown to capture close to 1 molar equivalent (or up 4.5 mol CO₂/kg absorbent) directly from moist air (>60 % RH) at room temperature and completely release the entire quantity of captured CO₂ upon co-evaporation of water at 70 °C affording concentrated CO₂ with a vapor content of 3 mol% and achieving a high working capacity with minimum temperature swing of 45 °C.