Interfacial modulation of oil microdroplets via ¹O₂ stimulated by exposed Fe clusters catalyzing ozonation of 1-adamantanecaboxylic acid for destabilization

Reactive oxygen species (ROS) generated on or near the oil droplet surface have remarkable potential in altering the structure of 1-adamantanecaboxylic acid (ACA) at the oil-water interface, facilitating separation of oil and water. To stimulate confined multi-phase ROS, a thermodynamic control strategy for ozone catalysis by Fe clusters anchored on nanoscale supports was developed. This strategy explored interfacial pollutant redistribution within film of microdroplets (10–20 μm in size) prepared with a high-speed shear emulsifier. Experimental results indicated that ¹O₂ selectively attacked carboxylic groups confined at the oil-water interface and two-electron migration pathway from ACA to adsorbed O₃ at interfacial oxygen vacancies (O_v) led to spatial redistribution with hydrophilic dihydroxylated intermediates via synchronous electrophilic substitution. ACA attached to interface of microdroplet is fueled by •OH and ¹O₂, achieving degradation at 89.84% within 30 min, and pseudo-first-order kinetics rate constants (k_obs) of 0.0793 min^–1. Thermodynamic analysis revealed that ¹O₂ reduced the Gibbs free energy (ΔG) by 23.98 kJ mol⁻¹ relative to that of •OH. This phenomenon is attributed to the narrow site distribution of Fe clusters, which enhances the overall electron utilization efficiency. These findings demonstrate the feasibility of manipulating ROS to regulate the distribution of interfacial species, representing a promising strategy for promoting the coalescence of oil microdroplets.