Preparation of metal–organic framework nanosheets with electron-rich groups for SO₂ adsorption

Metal–organic frameworks (MOFs), as a new type of porous crystalline materials, hold great promise for gas purification in electrical insulation equipment, especially for the selective capture of SO₂ produced from the decomposition of SF₆. However, challenges remain in the design and synthesis of MOF-based adsorbents with salient SO₂ adsorption performance due to the limited effective interactions with SO₂ molecules. This study reports the successful direct synthesis of two-dimensional (2D) MOFs nanosheets coordinated by Zr⁴⁺ and tridentate carboxylic organic ligands with nitrogen-containing electron-rich groups within the organic ligands. The resulting MOF nanosheets exhibit enhanced interactions with SO₂ molecules due to the spatial location and electronic properties of the nitrogen groups, thereby conducing to the adsorption of SO₂. Additionally, by precisely controlling the positioning of nitrogen groups, the Zr-BTB-NH₂ (BTB-NH₂: 1,1′:3′,1″-Terphenyl]-4,4″-dicarboxylic acid, 3,3″-diamino-5′-(3-amino-4-carboxyphenyl) and Zr-TPY (TPY: 4′-(4-carboxyphenyl)-[2,2′:6′,2″-terpyridine]-5,5″-dicarboxylic acid) MOFs synthesised in this study achieve differentiated SO₂ adsorption capacities of 39.3 cm³·g⁻¹ and 66.3 cm³·g⁻¹, respectively, surpassing those of several previously reported MOFs. This strategy provides a novel design strategy for developing efficient SO₂ absorbents and lays a foundation for the further development of absorbents promising for gas remediation in electrical insulation equipment.