Rational Engineering of Pillar‐Layered Co‐MOFs Through the Hard‐Soft Acid–Base Principle: Elucidating Highly Robust Flue Gas Desulfurization Under Dynamic Dry and Humidity

Efficient and selective SO 2 capture from flue gas, particularly under humid conditions, remains a significant challenge. Herein, we report the successful molecular design and construction of Pillar‐Layered Co 6 Cluster MOF (PLC‐Co), an ultramicroporous columnar layered MOF featuring a unique tfz‐d topology. Comprehensive studies revealed remarkable performance: single‐component isotherms showed a record SO 2 /CO 2 selectivity ratio exceeding 22 (5.71 mmol/g SO 2 vs. 0.36 mmol/g CO 2 at 0.1 bar), the highest reported among crystalline porous materials. Its high performance was validated in multicomponent breakthrough simulations and experiments, demonstrating sustained high‐efficiency SO 2 removal even under challenging 50% RH conditions. A combined experimental and computational study on the interaction between SO 2 and PLC‐Co single crystals has revealed the true adsorption sites of SO 2 within the material. This research elucidates the molecular adsorption mechanism and identifies specific interaction sites responsible for the observed unique selectivity. Furthermore, PLC‐CO exhibits excellent thermal and chemical stability, along with outstanding repeatability and regenerability. These findings highlight PLC‐CO as a highly promising material for practical flue gas desulfurization and showcase the effectiveness of topological design strategies for developing high‐performance porous materials for demanding gas separations.