Boosting trace SO₂ adsorption and separation performance by the modulation of the SBU metal component of iron-based bimetal MOFs

The development of effective adsorbents for the removal of trace SO2 from flue gas is extremely challenging. Herein, we investigated the effect of metal modulation on the SO2 adsorption and separation performance of MOF materials through PCN-250(Fe) (PCN stands for porous coordination network) and four bimetal PCN-250 materials, including PCN-250(Fe2Co), PCN-250(Fe2Ni), PCN-250(Fe2Mn) and PCN-250(Fe2Zn). Among the five materials, PCN-250(Fe2Ni) exhibited the highest SO2 uptake of 8.64 mmol g(-1) at 0.1 bar and 298 K, while PCN-250(Fe2Zn) showed the largest SO2/CO2 IAST selectivity of 49. Dynamic breakthrough experiments revealed that PCN-250(Fe2Zn) exhibited the most outstanding separation performances among the five materials, even with water vapor and real flue-gas compositions. Molecular simulations indicated that PCN-250(Fe2Zn) possessed additional adsorption sites and captured SO2 through multiple O & delta;-MIDLINE HORIZONTAL ELLIPSISH & delta;+ hydrogen bonds. Charge difference calculations showed that the non-overlapping charge distribution of Zn and O in PCN-250(Fe2Zn) made it more effective for SO2 capture.