Unveiling Mechanisms of Chlorinated Volatile Organic Compounds (CVOCs) and 1,4-Dioxane Sorption in Macrocyclic Materials: A DFT, MD, and Experimental Study.

The rational design of selective sorbents for removing contaminants such as chlorinated volatile organic compounds (CVOCs) and 1,4-dioxane from groundwater requires an in-depth understanding of the interplay between host-guest affinity and aqueous solvation. In this study, we integrate multiscale atomistic simulations with laboratory experiments to provide a comprehensive picture of adsorption onto five macrocycles. Our molecular dynamics (MD) simulations predict a marginal selectivity for CVOCs over 1,4-dioxane. To decipher critical phenomena such as cooperative adsorption and hydrophobic interactions that drive adsorption in various motifs, we simulate a range of adsorbate compositions and concentrations in water. Through density functional theory (DFT) calculations, we further examine the intrinsic host-guest binding affinities and study the interplay between underlying interactions such as hydrogen bonding, van der Waals interactions, and steric effects. Laboratory experiments reveal the high adsorption selectivity of CVOCs over 1,4-dioxane across the examined macrocycles at dilute, environmentally relevant concentrations. By resolving the model-experiment discrepancy, we demonstrate that the high energetic penalty of desolvating the hydrophilic 1,4-dioxane from water is the dominant factor controlling the relative uptake of adsorbates by macrocycles in water. This work establishes a design framework for next-generation sorbents, demonstrating that while strong intrinsic affinity is a prerequisite, the adsorption performance of macrocycles is governed by a complex interplay between host-guest chemistry, dynamic solvent effects, and multiple adsorption mechanisms.