Modified layered double hydroxides for efficient and reversible carbon dioxide capture from air

Direct air capture (DAC) is becoming a technically feasible negative emission technology; however, the fabrication of affordable adsorbents with large CO2 capacities, fast kinetics, and high sorption-desorption stability are of critical importance for the large-scale deployment of the DAC process. In this study, amine functionalized, aqueous miscible organic MgxAl-CO3 layered double hydroxide (LDH) nanosheets are used to efficiently and rapidly capture CO2 from ambient air. 3-[2-(2-Aminoethylamino)ethylamino]propyl-trimethoxysilane (TRI) treatment of highly dispersed LDH nanosheets produces a sorbent exhibiting an impressive adsorption capacity of 1.05 mmol g−1 at 25°C when exposed to 400 ppm CO2, which is 30% higher than equivalent amine-functionalized SBA-15 supports. CO2 uptake reaches 70% of this maximum capacity within 30 min and is twice as fast as supported polyamines. The highly dispersed LDH nanosheets provide excellent thermal, hydrothermal, and chemical stability, with negligible performance degradation after 50 adsorption-desorption cycles.