(456h) A Systematic Study of MOFs Containing Different N-Sites for Hydrogen Sulfide Adsorption

Hydrogen sulfide (H₂S), a corrosive toxic gas, presents a threat to human health, industrial processes, and the environment. Metal-organic frameworks (MOFs) have been shown to be promising candidates for H₂S adsorption due to their large surface area and structural tunability. However, efficiency, selectivity, and cyclability of H₂S capture present challenges that no group of MOFs has yet satisfied. Here, we report a series of N-modified UiO-66 type MOFs synthesized with ligands containing different N sites (amino, nitro, pyridine, pyrazine, and pyrazole). The introduced N sites with lone pair electrons will enhance the H₂S capacities for these MOFs at various degrees due to the different levels of binding strength between N sites and adsorbed H₂S molecules. Powder X-ray diffraction results confirm that all N-modified MOFs possess the same topology and show strong chemical stability to H₂S. H₂S adsorption from a stream of 1% H₂S in balance N₂ was measured using H₂S-thermal gravimetric analysis (H₂S-TGA). The results showed that all N-modified UiO-66 MOFs presented higher H₂S loadings. For example, UiO-66-3,5-PzoDC (pyrazole-modified UiO-66) adsorbed 0.958 mmol/g of H₂S, a loading five times higher than that of pristine UiO-66 (0.16 mmol/g). This talk will present H2S adsorption results fro this family MOFs, and the mechanism governing the adsorption process will be explored through in-situ infrared spectroscopy (in-situ IR) and X-ray photoelectron spectroscopy (XPS) experiments. The results suggest that the introduced N sites can act as favorable adsorption sites for H₂S. Additional density functional theory (DFT) simulation reveal which type of N sites exhibit the best H₂S adsorption behavior. Overall. this study provides insights into establishing basic rules for the design of MOFs with N-containing functional groups for H₂S adsorption.