Adsorption Desulfurization via π-Complexation with Ag+-Exchanged Anionic Metal–Organic Framework

The anionic metal–organic framework (Cu-BTC-DMA) was synthesized by the hydrothermal method. The extra-framework (CH3)2 NH2+ cations in Cu-BTC-DMA structure are movable and can be easily exchanged with Ag+. The Ag+-exchanged Cu-BTC-DMA was characterized through FT-IR, XRD, SEM, ICP, and N2 adsorption–desorption isotherms. The adsorption properties of Ag+-exchanged Cu-BTC-DMA with different Ag cation content were studied for the model fuel with different concentrations of thiophene. The results show that the Ag+-exchanged adsorbents show higher adsorption capacity for thiophene, which was ascribed to the introduction of Ag+ into Cu-BTC-DMA. Thiophene can interact with Ag+ via π-complexation. In addition, the Ag@Cu-BTC-DMA still shows the good performance of adsorption desulfurization in the presence of toluene. Ag@Cu-BTC-DMA (0.02 M) shows the highest adsorption capacity among the three adsorbents due to the high Ag+ amount and the almost integrated crystalline structure. In the process of regeneration, approximately 86% of the adsorptive capacity of Ag@Cu-BTC-DMA (0.02 M) can be recovered after four cycles.