Use of molecular simulation to design modification of a chromium-based MOF for adsorptive removal of inhalation anaesthetic agents

MIL-101-Cr-X (X = OH⁻, F⁻) has been reported to be the most suitable material so far for adsorptive removal of inhalation anaesthetic agents (IAA) sevoflurane and desflurane at the working conditions in hospital operation rooms. To further enhance its affinity and uptake capacity towards IAA, several structural modifications were proposed, and their isotherms were predicted using our molecular simulation approach adopted in our previous publication for the case of the pristine MIL-101-Cr (X = F⁻, OH⁻) structure. The proposed modifications include (1) grafting the metal-cluster site with coordinated NH₃ ligands to produce MIL-101-Cr@NH₃ (X = F⁻, OH⁻), (2) anion exchange of the fluorine atom bonded to chromium with chlorine to synthesize MIL-101-Cr (X = Cl⁻), and (3) functionalization of the benzene rings of the ligand linkers in the MOFs with amino- and nitro- groups in order to form NH₂-MIL-101-Cr (X = Cl⁻) and NO₂-MIL-101-Cr (X = Cl), respectively. Simulated adsorption isotherms of IAA on these modifications were verified by the experimental results using the standard volumetric technique and they clearly demonstrated that MIL-101-Cr@NH₃ (X = F⁻, OH⁻) possesses the highest equilibrium capacity for IAA. This observation can be attributed to the electron-transfer contribution of the coordinated ammonium molecules to the unsaturated coordinated sites of the MOF while doing away with steric hindrance inside the pore cages. The new compound can significantly enhance the economy of adsorptive removal of IAA from vented gas mixtures.