Density functional theory study on the enhanced adsorption mechanism of VOCs by Cu4 cluster decorated UiO-66

Abstract

Volatile organic compounds (VOCs) are a class of air pollutants that greatly harm human health and the ecological environment, convenient and effective treatment of VOCs has become a challenge. This work proposed a transition metal cluster decorated UiO-66 (a typical type of metal-organic framework) as the effective adsorbent for the purification of VOCs with typical functional groups based on density functional theory (DFT) calculations. The results show that the VOCs adsorption energy on the modified UiO-66 increased significantly, especially for Cu4 cluster-modified UiO-66, and the adsorption energy of trichloroethene is greater than that of the other considered VOCs, which may be induced by halogens or carbon-carbon double bond in trichloroethene. We compared chloromethane, chloroethylene, and ethylene and found that VOCs with carbon-carbon double bond have stronger adsorption energy, increasing with the number of chlorine atoms. The density of states (DOS), Hirshfeld charge analysis, and orbital distribution further confirm the charge distribution in UiO-66 after the decoration of the Cu4 cluster. Cu4 cluster can act as a bridge to promote the formation of chemical bonds between UiO-66 and VOCs molecules. Therefore, Cu4 cluster-modified UiO-66 can be a promising VOCs adsorption material, especially for vinyl chloride molecules.