Interrogating the Metal Identity Effect of Isostructural NU-1801 Frameworks on Toxic Gas Capture with Moisture-Enhanced Feature

The effective capture of toxic industrial chemicals (TICs), particularly at low concentrations and under humid conditions, is essential for industrial chemical waste management and environmental hazard remediation. Among existing sorbents, metal-organic frameworks (MOFs) are promising materials for TIC capture, yet a significant gap remains in the design principles. Herein, we leveraged reticular chemistry to construct isostructural NU-1801 frameworks with Y₆, Zr₆, Hf₆, Ce₆, and Th₆ clusters, providing a systematic platform to elucidate the structure-property relationships among metal identity, framework stability, and adsorption performance for TICs. Among the five analogs, NU-1801(Zr) had the highest structural stability and adsorption performance for SO₂ and NH₃. Breakthrough experiments demonstrated that NU-1801(Zr) exhibited moisture-enhanced behavior for SO₂ and NH₃ capture driven by the formation of sulfate and ammonium species, respectively. Molecular studies revealed that the binding pockets of SO₂ and NH₃ were located at the metal carboxylic cluster, with μ₃-OH species serving as the main binding sites. Additionally, coadsorption binding geometries of H₂O + SO₂ and H₂O + NH₃ are more thermodynamically favorable than the formation of a pure H₂O network, explaining the experimentally observed formation of sulfate and ammonia species. This work demonstrates the critical role of metal identity in the rational design of isostructural MOF adsorbents for practical TIC capture.