A comprehensive study about functionalization and de-functionalization of MOF-808 as a defect-engineered Zr-MOFs for selective catalytic oxidation.

In metal-organic frameworks (MOFs), confined space as a chemical nanoreactor is as essential as coordinatively unsaturated metal site catalysis. The properties of MOFs can be adjusted through the incorporation of functional groups and open metal sites in frameworks that can modify the catalytic performance. In this regard, a set of defect-engineered MOFs, Ex-MOF-808(NH, NO, H) and Mix-MOF-808(NH, NO, H), were synthesized by ultrasonic-assisted linker exchange approach (Ex-MOFs) and solvothermal mixing ligand method (Mix-MOFs), respectively. Further, the relationship between the preparation method, structural properties, and catalytic efficiency of the prepared materials in the selective oxidation of methyl phenyl sulfide (MPS) has been investigated. By analyzing zeta potential, it was found that in the exchange method, the amount of defect and functional groups on the surface of MOFs are more than in the mixing method, which also affects the catalytic activity. In our contribution, mix-MOF-808(NO) carrying nitro groups at their organic linkers, which has a well-dispersion of nitro groups at the framework exhibits selective conversion of MPS to sulfone (91 %). Furthermore, the performance of stable heterogeneous catalysts was investigated for three cycles, which demonstrated their great potential for advanced catalytic oxidation.