The efficient removal of trace sulfur dioxide (SO2) from wet flue gas remains a critical challenge for porous adsorbents. In particular, high humidity imposes stricter requirements on the robustness of the framework and selective adsorption, degrading sorbent materials and SO2 capture performance under realistic conditions. Herein, we report a zirconium metal–organic framework (Zr-MOF), BUT-196 (BUT = Beijing University of Technology), isoreticular to UiO-68, constructed from a carbazole-containing dicarboxylate ligand, 4,4′-(5,11-dihydroindolo3,2-bcarbazole-6,12-diyl)dibenzoic acid, and 12-connected Zr6 cluster. Featuring a robust fcu network with a tailored pore environment, BUT-196 exhibits steep low-pressure SO2 uptake at ambient temperature. Postsynthetic modification of the carbazole NH site with bromoacetic acid introduces carboxylic acid groups without disrupting the framework integrity, yielding BUT-196-COOH. Notably, BUT-196-COOH achieves a dramatically enhanced SO2 adsorption capacity under humid conditions. Breakthrough experiments revealed that, at 90% relative humidity, the SO2 breakthrough time increases from ∼800 to ∼2300 min g–1, both for single-component SO2 and simulated quadruple flue gas mixtures. Further, BUT-196-COOH maintains excellent selectivity and stable cyclic performance. This study highlights that rational pore functionalization can transform high humidity from a competing factor into a cooperative contributor for trace SO2 capture within a robust framework, offering a viable strategy to MOF sorbent design for wet flue gas desulfurization.
He et al. (2026) studied this question.