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

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 (Q_st = 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.