Preparation of amino-functionalized CoAl-LDH/palygorskite hierarchical composites for CO2 capture

Layered double hydroxides (LDH) are regarded as an outstanding adsorbent with the ability to capture CO₂. Nevertheless, the stacking and curling of CoAl-LDH significantly impact the CO₂ adsorption performance. In this study, CoAl-LDH were synthesized on a rigid palygorskite (Pal) framework to form a hierarchical CoAl-LDH/Pal composite, which effectively reduced the original particle size of CoAl-LDH and addressed the drawbacks. Subsequently, polyethylene imine (PEI) was impregnated onto the surface of CoAl-LDH/Pal to fabricate PEI/CoAl-LDH/Pal adsorbent, further improving the CO₂ capture performance. Finally, the mechanism of CO₂ adsorption was also elaborated. The PEI/CoAl-LDH/Pal demonstrated a higher equilibrium adsorption capacity and a longer breakthrough time for CO₂ capture, with the adsorption capacity reaching 158.8 mg/g and increasing by 8 times compared to that of CoAl-LDH/Pal. Herein, CO₂ was adsorbed on the surface of PEI/CoAl-LDH/Pal in the forms of bicarbonate and amino carboxylate. Additionally, PEI/CoAl-LDH/Pal exhibited excellent regeneration performance and maintained the adsorption capacity over 9 cycles, which is anticipated to be a promising candidate for CO₂ capture.