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., Cu-3[C6H3(CO2)(3)](2) (Cu-BTC), Cu[O2C-C6H4-CO2] (Cu-BDC), Cr(OH) [O2CC6-H-4-CO2] (Cr-BDC), and Cr3F(H2O)(3)O[C6H3(CO2)](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,pi-electron number and the electron density on the S-atom. Finally, the used MOF can be easily regenerated by solvent washing and recycled at least five times.