Postsynthetic metal exchange of Ti(IV) into a series of mixed ligand UiO-MOFs: study of their catalytic applications

Abstract

Herein, we report mixed-ligand, mixed-metal highly porous UiO-derivatives (UiO = University of Oslo) obtained by postsynthetic metal exchange (PSE)1. Ti atoms were embedded into the Zr-cluster of UiOs (Zr6O4(OH)4) by treatment with TiCl4(THF)2, obtaining up to 50% atom exchanged. After PSE, the crystallinity and morphology of the UiO-materials were maintained, indicating that Zr-Ti exchange did not alter the structural properties of the MOFs. Post-functionalized MOFs have demonstrated attractive properties for catalytic applications2. Herein Zr- and ZrTi-UiO-MOFs have been applied as catalysts for the isomerization of -pinene epoxide and citronellal. High conversions and good selectivities were obtained for both substrates (70 and 80% respectively in 24 hours). The presence of Ti into the catalyst improves the reactivity obtaining higher conversions, particularly in the case of citronellal, while the presence of NH2 group has minor effect on the reactions.