Molecular engineering to fabricating dinuclear-crossed secondary building units in metal-organic frameworks for aromatic sulfur-containing compounds adsorption

Aromatic sulfur-containing compounds are main constraints for liquid hydrocarbon fuels upgrading furtherly. Efficient adsorption of the sulfur-containing compounds by metal–organic frameworks (MOFs) is still a challenging because of single and inert adsorptive sites. We herein represent a new strategy, constructing dinuclear-crossed secondary building units (SBUs) in MOFs, for generating Cu(I) and Cu-coordination-unsaturated sites (Cu-CUS). The high-performance Cu(I) and Cu-CUS sites are controllable by modulating the organic ligands molar ratio of 1,3,5-benzenetricarboxylic acid / 4-pyrazolecarboxylic acid (BTC/PyC). The optimal Cu-BTC/PyC-1/1 with abundant Cu(I), Cu-CUS, and large surface areas thus exhibits dibenzothiophene adsorption capacity of 51.11 mg S/g. The result shows 100.3% and 47.8% increased adsorption capacity comparison with that of sole Cu-PyC (25.52 mg S/g) and Cu-BTC (34.57 mg S/g) respectively. The high adsorption capacity originates from electron-transfer mechanism between empty-electron-orbital Cu(I)/Cu-CUS and electron-enriched aromatic sulfur-containing compounds. The molecular engineering for building multiple adsorptive sites by dinuclear-crossed SBUs strategy exhibits great promising for MOFs-based adsorbents design.