Highly Reversible and Selective Capture of Trace SO 2 in a Scalable Aluminum-Based Metal–Organic Framework

The desulfurization of flue gas requires sorbents capable of selective and reversible SO2 capture. However, top-performing materials operate through either strong binding sites or the use of narrow pores, leading to difficulties in desorption and materials regeneration. Here, we report the efficient capture of trace SO2 using a robust and scalable aluminum-based metal–organic framework, MIL-120, which shows an exceptional SO2 uptake of 2.1 mmol g–1 at 2500 ppm and 298 K, coupled with optimal heats of adsorption (19–42 kJ mol–1) and fully reversible desorption at room temperature. Direct visualization of adsorbed SO2 molecules reveals host–guest and guest–guest interactions, collectively affording an SO2 packing density of 1.92 g cm–3, formally surpassing that of solid SO2 (1.62 g cm–3). Breakthrough experiments demonstrate that MIL-120 exhibits remarkable trace SO2 capture in the presence of dry or wet NO2 (another corrosive gas present in flue gas) with a record dynamic selectivity of 124, confirming the potential for MIL-120 to separate SO2/NO2 mixtures. This work sets a new benchmark for sorbent materials for reversible trace SO2 capture and separation.