(465e) Trivalent metals on MOFs for SO2 adsorption

SO₂ presents a threat to human health, industrial processes, and the environment. Metal-organic frameworks (MOFs) have been shown to be promising candidates for SO₂ adsorption due to their large surface area and structural tunability. However, developing MOFs with high SO₂ capacity especially at low partial pressure as well as excellent selectivity remains a challenge. Here, we report three pairs of Al-MOFs with ligands containing different N, O, and S functional sites. The introduced N, O, and S functional sites will enhance the SO₂ capacities for these MOFs at various degrees due to the different levels of binding strength between them with adsorbed SO₂ molecules. Powder X-ray diffraction results confirmed that these modified MOFs possessed the same topology and show strong chemical stability to SO₂. SO₂ adsorption from a stream of 0.1% SO₂ in balance N₂ was measured using a home-built breakthrough system. The results showed that all functionalized Al-MOFs presented higher SO₂ loadings than parent CAU-10. Interestingly, MOFs with heterocyclic functional sites exhibited high uptake of SO₂ than their corresponding ones with aryl functional sites. For example, CAU-10-3,5-PDC adsorbed 0.41 mmol/g of SO₂, higher than that of CAU-10-NH₂ (0.25 mmol/g). This talk will present SO₂ adsorption results for these pairs of Al-MOFs, and the mechanism governing the adsorption process will be explored through Attenuated total reflection infrared spectroscopy (ATR-IR) experiments. The results suggest that the introduced functional sites can act as favorable adsorption sites for SO₂. Additional density functional theory (DFT) simulation reveals which type of functional sites exhibit the best SO₂ adsorption behavior. Overall, this study provides insights into establishing basic rules for the design of Al-MOFs with N, O, or S-containing functional groups for SO₂ adsorption.