Probing the correlations between the defects in metal–organic frameworks and their catalytic activity by an epoxide ring-opening reaction

Abstract

Seven Zr/Hf-based MOFs with different degrees of defects were obtained by modulating the synthetic conditions. The number of missing linkers in these MOFs was calculated based on potentiometric acid-base titration. The number of defects was found to correlate quantitatively with the catalytic activity of UiO-type MOFs for an acid-catalyzed epoxide ring-opening reaction. More importantly, we were able to identify a MOF with inherent defective Zr6 nodes, which showed great activity and regio-selectivity for the epoxide ring-opening reaction.

Catalytic Transfer Hydrogenation of Biomass‐Derived Carbonyls over Hafnium‐Based Metal–Organic Frameworks

“…UiO‐66‐NH 2 (Hf) is reported here for the first time, as far as we know. UiO‐67(Hf) with biphenyl‐4,4‐dicarboxylate as organic linker was prepared by following the reported procedure and by using benzoic acid as modulator . As for the related UiO‐66(Zr), the synthetic procedure used here is the same as the one employed in the synthesis of UiO‐66(Hf) to assure a similar degree of defects in both frameworks and a fair comparison of metal activity.…”

“…This fact has probably slowed down development of practical applications of Hf‐MOFs. The use of “modulators” in MOFs synthetic procedures allows the construction of crystalline solid materials along with the intentional positioning of defects in the framework that, in several cases, appear to correlate with their catalytic activity . This modulator strategy is particularly successful for building crystalline Hf‐MOFs.…”

“…Acetic acid, water, and formic acid have been used as modulators in the synthesis of MOF UiO‐66(Hf). Benzoic acid is reported to allow the synthesis of MOF UiO‐67(Hf). Hf‐MOF‐808 with the trimesate linker makes use of formic acid for its preparation …”

“…Benzoic acid is reported to allow the synthesis of MOF UiO‐67(Hf). Hf‐MOF‐808 with the trimesate linker makes use of formic acid for its preparation …”

Postsynthetic ionization of an imidazole-containing metal–organic framework for the cycloaddition of carbon dioxide and epoxides

“…7 e On the other hand, the catalytic activities of 1 for the coupling reactions of 1,2-epoxyhexane or styrene oxide and CO 2 were investigated, which further confirmed the existence of Brønsted-acid (Zr–OH/Zr–OH 2 ) sites in 1 (Table S5†). 16 Moreover, it was noted that halohydrocarbons, such as epichlorohydrin, could react with the imidazole-based framework to form a complex ionic catalyst that self-catalyzes the reaction based on a similar mechanism. 18 b …”