Engineering Zigzag-Arranged Guest Chains in One-Dimensional Nanochannels Featuring Open Metal Sites for Trace SO2 Capture.

The design of adsorbents for efficient trace SO2 capture from flue gas is critical in flue gas pollution control. Fully exploiting the synergy of host-guest and guest-guest interactions in porous adsorbents holds promise for boosting trace guest molecule capture, yet remains challenging. Herein, we report a stable metal-organic framework, [Cu3(Fuma)2(OH)2] (denoted as Cu-Fuma), featuring ultramicroporous one-dimensional channels densely functionalized with open metal sites for efficient trace SO2 capture. At 298 K and 1 bar, Cu-Fuma exhibits a high SO2 uptake capacity (81 cm3·g-1) and pronounced affinity over CO2 at low pressure. It demonstrates a high IAST-predicted selectivity for SO2/CO2 (72 for a V:V = 0.2:99.8 mixture) coupled with a moderate isosteric heat of adsorption (Qst = 31.7 kJ·mol-1), indicating an optimal balance between adsorption selectivity and regeneration energy. Dynamic breakthrough experiments confirm its capability to selectively capture trace SO2 (∼0.2%) from a CO2-rich stream. Moreover, Cu-Fuma exhibits excellent stability and regeneration, rendering it a promising candidate for industrial SO2 capture. Computational simulations reveal that the confined pore environment strengthens electrostatic host-guest interactions for polar SO2, while the high-density arrangement of open metal sites facilitates favorable guest-guest interactions, synergistically enhancing SO2 adsorption selectivity and capture performance.