Molecular simulation study of all-silica zeolites for the adsorptive removal of airborne chloroethenes

Chloroethenes are produced and consumed in various industrial processes. As the release of these compounds into air, water, and soils can pose significant risks to human health and the environment, different techniques have been exploited to prevent or remediate chloroethene pollution. Although several previous experimental and computational studies investigated the removal of chloroethenes using zeolite adsorbents, their structural diversity in terms of pore size and pore topology has hardly been explored so far. In this work, molecular simulations using validated empirical force field parameters were used to study the gas-phase adsorption of chloroethenes in 16 structurally distinct zeolite frameworks. As all these frameworks are synthetically accessible in high-silica form, the simulations used purely siliceous zeolite models. In the most relevant concentration range (0.1 to 10 ppm by volume), substantial uptakes of tri- and tetrachloroethene were computed for several zeolite frameworks, prominently EUO, IFR, MTW, MOR, and BEA. In contrast, vinyl chloride uptakes were always too low to be of practical relevance for adsorptive removal. For selected frameworks, simulation snapshots were analyzed to investigate the impact of pore shape and, at higher uptakes, guest-guest interactions on the adsorption behavior. Hence, this study not only identifies zeolites that should be prioritized in future investigations, but also contributes to the microscopic understanding of chloroethene adsorption in crystalline microporous materials.