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

Abstract

Direct air capture (DAC) is becoming a technically feasible negative emission technology; however, the fabrication of affordable adsorbents with large CO 2 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 Mg x Al-CO 3 layered double hydroxide (LDH) nanosheets are used to efficiently and rapidly capture CO 2 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 CO 2 , which is 30% higher than equivalent amine-functionalized SBA-15 supports. CO 2 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. Amine monolayer-tethered, exfoliated layered double hydroxides are synthesized The adsorbent shows an CO 2 capacity of 1.05 mmol g −1 in simulated air CO 2 uptake reaches 70% of this maximum capacity within 30 min Negligible performance degradation is observed after 50 cycles Zhu et al. synthesize modified layered double hydroxides (LDHs) to capture CO 2 from ambient air. Exposed hydroxyl groups on LDHs react with aminosilanes to form amine monolayer grafted nanosheets, allowing ultrafast CO 2 capture. Platelet size, thickness, and exfoliated morphology have a significant impact on obtaining the optimal amine grafting.