Post modification of Oxo-clusters in robust Zirconium-Based metal organic framework for durable SO2 capture from flue gas

Abstract

• SO 2 capture from flue gas in MOF-808 and multi-amine carboxylic acid (EDTA) decorated MOF-808 is examined. • Ultra-high SO 2 capture efficiency and highly reversible SO 2 capture ability are achieved in EDTA-MOF-808 under real condition. • The SO 2 adsorption configuration in EDTA-MOF-808 is explained in detail by DFT theoretical calculations. The efficient capture of SO 2 after the combustion of fossil fuels is of great challenge as the low SO 2 concentration (<500 ppm) and coexisting with CO 2 , water, O 2 in flue gas. Robust zirconium-based MOFs possessing accessible polar sites usually have high SO 2 adsorption capacity but poor durably in adsorption desulfurization due to the acidic sulfate deposition on the Zr-O cluster. Herein, a Zr-O cluster post-modification method was introduced in a Zr-MOF (MOF-808) to form EDTA-MOF-808 (EDTA, ethylene diaminetetraacetic acid) for selective and durable removal of SO 2 . The introduction of EDTA not only improve their SO 2 adsorption capacity, but also sharply increase their SO 2 /CO 2 selectivity (57.2 vs 8.9) and SO 2 /N 2 selectivity (1915.8 vs 292.7) at low SO 2 partial pressure. Moreover, the synergistic effects of dipole and hydrogen bonding interaction between SO 2 and EDTA in EDTA-MOF-808 make the capture of SO 2 in a reversible manner, which can prevent the formation of S(VI) species in Zr-MOF. DFT calculation confirmed that SO 2 was interacted with EDTA through moderate dipole–dipole interaction (S(SO 2 ) with N(EDTA)) and hydrogen bonds (H(–COOH) with O(SO 2 )). Systematic investigations including thermodynamic SO 2 adsorption, dynamic breakthrough experiments, stability tests and DFT-calculations in both MOF-808 and EDTA-MOF-808 confirmed the efficient performance of post modification of Zr-O clusters with EDTA in Zr-MOFs for durable SO 2 capture.