In Silico Tuning of the Pore Surface Functionality in Al-MOFs for Trace CH₃I Capture

Aluminum (Al)-based metal-organic frameworks (MOFs) have been shown to have good stability toward γ irradiation, making them promising candidates for durable adsorbents for capturing volatile radioactive nuclides. In this work, we studied a series of existing Al-MOFs to capture trace radioactive organic iodide (ROI) from a gas composition (100 ppm CH₃I, 400 ppm CO₂, 21% O₂, and 78% N₂) resembling the off-gas composition from reprocessing the used nuclear fuel using Grand canonical Monte Carlo (GCMC) simulations and density functional theory (DFT) calculations. Based on the results and understanding established from studying the existing Al-MOFs, we proceed by functionalizing the top-performing CAU-11 with different functional groups to propose better MOFs for ROI capture. Our study suggests that extraordinary ROI adsorption and separation capability could be realized by -SO₃H functionalization in CAU-11. It was mainly owing to the joint effect of the enhanced pore surface polarity arising from -SO₃H functionalization and the μ-OH group of CAU-11.