Engineering Zigzag-Arranged Guest Chains in One-Dimensional Nanochannels Featuring Open Metal Sites for Trace SO ₂ Capture

The design of adsorbents for efficient trace SO 2 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, [Cu 3 (Fuma) 2 (OH) 2 ] (denoted as Cu-Fuma), featuring ultramicroporous one-dimensional channels densely functionalized with open metal sites for efficient trace SO 2 capture. At 298 K and 1 bar, Cu-Fuma exhibits a high SO 2 uptake capacity (81 cm 3 ·g –1 ) and pronounced affinity over CO 2 at low pressure. It demonstrates a high IAST-predicted selectivity for SO 2 /CO 2 (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 SO 2 (∼0.2%) from a CO 2 -rich stream. Moreover, Cu-Fuma exhibits excellent stability and regeneration, rendering it a promising candidate for industrial SO 2 capture. Computational simulations reveal that the confined pore environment strengthens electrostatic host–guest interactions for polar SO 2, while the high-density arrangement of open metal sites facilitates favorable guest–guest interactions, synergistically enhancing SO 2 adsorption selectivity and capture performance.