Trace SO₂ capture and conversion by a zirconium MOF

Whereas 95 % of SO₂ from flue gas streams is removed by conventional flue-gas desulfurization (FGD) technologies, multi-stage energy-intensive and waste-generating scrubbing is needed to meet current emission standards (≤35 ppm) and requirements for processes such as CO₂ capture and denitrification (<10 ppm). Despite the availability of numerous methods and materials for desulfurization, the integrated capture and conversion of trace SO₂ remains challenges. Herein, we report that the layered metal-organic framework (MOF) BUT-86 captures trace (100 ppm) SO₂ from simulated flue gas to afford effluent SO₂ levels < 10 ppb. Performance is driven by exceptional SO₂/CO₂ selectivity at 80 % RH. Captured SO₂ can be subsequently removed by room temperature conversion to 2-hydroxypropane-2-sulfonic acid to regenerate BUT-86. Reactive SO₂ binding involving bisulfite formation that requires the presence of adsorbed water drives the performance of BUT-86, the first sorbent that enables integrated trace SO₂ capture and conversion from flue gas.