Exploring MIL-101 (Cr) and Its Polymeric Composites as Potential Adsorbents for Volatile Iodine from Nuclear Off-gas: A Detailed Experimental and Computational Study

Abstract

Owing to the rapid growth of nuclear energy as a sustainable, affordable, and clean energy source, the entrapment of radioactive iodine released from the nuclear off-gas stream is considered a vital concern. We view MOFs as potential futuristic adsorbents for this remedy. Herein, we examined the gravimetric iodine adsorption characteristics of radiation and chemically stable MIL-101(Cr) and its polymeric composites with variation of temperatures. The saturation adsorption capacity shown by pristine MIL-101(Cr) is 4.1 g I₂ g^–1, and the saturation capacity of composites varies based on MIL-101(Cr)’s concentrations. MIL-101(Cr)@PES 2:1 shows an uptake capacity of 2.1 g I₂ /g_bead, which is ∼ 350% superior to the reported HKUST-1@PES and ∼150% higher compared to MOF-808@PVDF_0.7. Based on various spectroscopic studies and DFT calculations, probable host–guest interactions leading to enhanced I₂ adsorption have been elucidated. The open Cr metal site acts as the initial adsorption site for I₂ that gets converted into iodide and afterward to higher polyiodide through the transfer of charge from the host matrix. These findings suggest that MIL-101(Cr) can be considered one of the potential alternate adsorbents for radioactive iodine.