Improving the adsorption capacity of amino-modified Mg-Al LDH using a combined DFT and experiment

Abstract

The adsorption of CO2 using layered double hydroxides (LDHs) such as Mg-Al LDH is both technically feasible and economical. Although some approaches to the modification of LDHs have proved fruitful, there is still a need for further improvement in the adsorption capacity of modified LDHs. Here, a new optimization direction for amino-modified Mg-Al-LDHs is proposed based on using DFT and AIMD simulations to elucidate the mechanism of CO2 diffusion. The proposed approach was then evaluated experimentally. Theoretical calculations showed that the adsorption energy of ordinary amino-modified LDHs was low, at − 0.56 eV. DFT simulations showed that the number of interlayer water molecules affects the CO2 adsorption energy, with the optimum adsorption energy of − 0.78 eV obtained in the presence one interlayer water molecule. Experimental analysis showed that the drying time affects the amount of interlayer water and thus the CO2 adsorption capacity, with the maximum adsorption capacity of 1.7424 mmol/g obtained after drying for 5 h. This study provides useful insights towards the development of materials such as Mg-Al LDHs for efficient CO2 adsorption and highlights the critical role of interlayer-bound water on the adsorption performance.