Mixed-Linker Isoreticular Zn(II) Metal-Organic Frameworks as Br?nsted Acid-Base Bifunctional Catalysts for Knoevenagel Condensation Reactions

Multicomponent metal-organic frameworks (MOFs) have received an increasing amount of attention due to their potential to produce new topologies, pore metrics, and functionalities compared to MOFs with a single metal cluster and one organic linker. Herein, five isoreticular Zn MOFs were obtained by mixing two types of linear ditopic linkers in a one-pot solvothermal synthesis. Interestingly, in the resulting Zn MOFs a six-connected cyclic trinuclear Zn(II) cluster and an eight-connected linear trinuclear Zn(II) cluster coexist, leading to an uncommon (6,8)-connected network. Catalytic activities toward the solvent-free Knoevenagel reactions were observed for all of these MOFs. Further experimental and computational studies suggest that they are Bronsted acid-base bifunctional catalysts. Through chemical modifications of dicarboxylate ligands, including their aromatic backbones and substituents, we have successfully implemented reticular chemistry for the modulations of pore sizes, surface areas, and catalytic performances in a series of four-component isoreticular MOFs.

Automated summary

Multicomponent metal-organic frameworks (MOFs) have attracted attention for their potential to create new topologies, pore metrics, and functionalities compared to MOFs with a single metal cluster and organic linker. In this study, five isoreticular Zn MOFs were synthesized using a one-pot solvothermal synthesis method by mixing two types of linear ditopic linkers. The resulting MOFs exhibited catalytic activity in solvent-free Knoevenagel reactions and were found to be Bronsted acid-base bifunctional catalysts. Chemical modifications of dicarboxylate ligands were used to modulate the pore sizes, surface areas, and catalytic performances of a series of four-component isoreticular MOFs.