Adsorption of 2-Chloroethyl Ethyl Sulfide on Silica: Binding Mechanism and Energy of a Bifunctional Hydrogen-Bond Acceptor at the Gas–Surface Interface

Abstract

This work investigates the fundamental nature of sulfur mustard surface adsorption by characterizing interfacial hydrogen bonding and other intermolecular forces for the surrogate molecule (simulant) 2-chloroethyl ethyl sulfide (2-CEES). Adsorption at the surface of amorphous silica is the focus of this work because of silica’s low chemical reactivity, well-known properties, and abundance in the environment. 2-CEES has two polar functional groups, the chloro and thioether moieties, available to accept hydrogen bonds from free surface silanol groups. Diethyl sulfide and chlorobutane are also investigated to independently assess the role of the chloro and thioester functionalities in the overall adsorption mechanism and to explore the interplay between the charge transfer and electrostatic contributions to total hydrogen-bond strength. Our approach utilizes infrared spectroscopy to study specific surface–molecule interactions and temperature-programmed desorption to measure the activation energy for desorption of adsorbed molecules. Our results indicate that 2-CEES adsorbs to silica by hydrogen bonding through either the chloro or thioether moieties but is unable to form a more stable configuration in which both polar groups interact simultaneously with adjacent silanol groups. The activation energy for desorption of 2-CEES is nearly 43 kJ/mol, driven by both strong hydrogen bonding and other non-bonding interactions. A systematic study of chloroalkanes reveals that each methylene group contributes approximately 5–8 kJ/mol to the overall desorption energy.

A molecular picture of surface interactions of organic compounds on prevalent indoor surfaces: limonene adsorption on SiO2

“…1a). Based on similar results, previous infrared studies have also reported the presence of hydrogen bonding between other molecules and the SiO 2 surface 20,33,34. A detailed peak assignment for limonene adsorbed on hydroxylated SiO 2 is provided in the ESI (Table S1†) and shows that the vibrational frequencies are close to that for limonene in the gas and liquid phases.…”

Reaction Mechanism of Nerve-Agent Decomposition with Zr-Based Metal Organic Frameworks

“…The defective UiO-66 SBU used in this work is based on that described by Ling and Slater, and exhibits a hydroxide ligand saturating one of the undercoordinated Zr atoms, with the nerve agent bound on the other undercoordinated Zr atom (Figure a). This SBU is used to simulate future ultrahigh-vacuum (UHV) experiments in which a customary thermal treatment of the surface removes physisorbed water and other adsorbates prior to exposure to the nerve agent. , In UHV conditions, the Zr–OH catalyst in Figure a can also be generated via dissociation of a coordinated aqua ligand on the defective SBU, as shown in the figure. The water dissociation reaction is exothermic by 19.0 kJ/mol and proceeds over a low barrier of 30.0 kJ/mol.…”

“…A final note in our discussion of the general base hydrolysis mechanism is that under ambient conditions, the presence of atmospheric water will likely facilitate this pathway with respect to the one not mediated by water described before. On the other hand, the dry mechanism will likely be operational in fundamental gas-surface experiments under ultrahigh vacuum, where customary thermal treatment cleans the surface of the catalyst prior to exposure to nerve agents or simulants. , …”

Effective removal of chemical warfare agent simulants using water stable metal–organic frameworks: mechanistic study and structure–property correlation

“…Among several methods to remove toxic chemicals, adsorptive removal is signicant, due to its simple operation and cost effectiveness. 34,[41][42][43][44][45][46][47][48][49] There are few reports where MOFs are used for this purpose, but the mechanism of these types of adsorption processes is still ambiguous. In the present work, we have used Zr-based MOFs (NU-1000 and UiO-67) for the efficient adsorption and removal of CWA simulants, (or namely) 2-CEES and DMMP from the aqueous medium.…”