Adsorption Behavior of Metal–Organic Frameworks for Thiophenic Sulfur from Diesel Oil

Four metal–organic frameworks (MOFs) are synthesized using two different metal centers and two different organic ligands, viz., Cu3[C6H3(CO2)3]2 (Cu-BTC), Cu[O2C–C6H4–CO2] (Cu-BDC), Cr(OH)[O2C–C6H4–CO2] (Cr-BDC), and Cr3F(H2O)3O[C6H3(CO2)3]2 (Cr-BTC). Their adsorption behaviors for thiophenic sulfurs in model diesel oils are systematically investigated at mild temperatures and follow the order Cu-BTC > Cr-BDC > Cr-BTC ≫ Cu-BDC. Meanwhile, the adsorption capacity of different sulfur compounds follows the order dibenzothiophene (DBT) > benzothiophene (BT) > 3-methylthiophene (3-MT). The MOFs adsorption mechanism is regarded as a combined effect of many factors involving appropriate framework structure, suitable pore size and shape, and exposed Lewis acid site matching the S-compound to be adsorbed. The difference in adsorptive activity among the organosulfurs is mainly ascribed to their π-electron number and the electron density on the S-atom. Finally, the used MOF can be easily regenerated by solvent washi...