Linker-Functionalized Zr-Based UiO-66 Metal-Organic Frameworks: Tuning Acidity for Enhanced Catalytic Dimerization of Cyclohexanone

The precise manipulation of pore structure, organic linkers, and disposition of active and coactive sites in metal-organic frameworks (MOFs)-based materials allows the designing of materials with tailored catalytic properties. However, studies that address their kinetic, dynamic, and mechanistic roles in target reactions are scarce. The development of a new functionalization method to introduce acidity into MOFs is established for heterogeneous catalysis. Exploring the effect of ligand functionalization in MOF type UiO-66(Zr) impacts its ability to catalyze the dimerization reaction of cyclohexanone. Upon treatment with a series of linkers and the addition of HCl, chemically stable MOF structures such as UiO-66 can be protonated, resulting in an acidic group attached to aromatic terephthalate linkers in the structure. A general synthetic strategy has been developed to produce functionalized UiO-66-FG compounds [FG = NH₂, NO₂, Br, OH, and (OH)₂]. The functionalized acidic frameworks present enhanced catalytic activity toward the self-condensation of cyclohexanone. Investigating these aspects can provide valuable insights into how the functionalization of MOFs performs in real-world self-condensation scenarios and help in optimizing their practical applications.