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

Abstract

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^δ−⋯H^δ+ 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.