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Systematic Engineering of Single Substitution in Zirconium Metal–Organic Frameworks toward High-Performance Catalysis

Huang, Ning, Yuan, Shuai, Drake, Hannah, Yang, Xinyu, Pang, Jiandong, Qin, Junsheng, Li, Jialuo, Zhang, Yingmu, Wang, Qi, Jiang, Donglin, Zhou, Hong-Cai
Journal of the American Chemical Society 2017 v.139 no.51 pp. 18590-18597
alcohols, byproducts, catalytic activity, coordination polymers, ketones, models, oxidation, porphyrins, zirconium
Zirconium-based metal–organic frameworks (Zr-MOFs) exhibit great structural tunability and outstanding chemical stability, rendering them promising candidates for a wide range of practical applications. In this work, we synthesized a series of isostructural PCN-224 analogues functionalized by ethyl, bromo, chloro, and fluoro groups on the porphyrin unit, which allowed us to explicitly study the effects of electron-donating and electron-withdrawing substituents on catalytic performance in MOFs. Owing to the different electronic properties of ethyl, bromo, chloro, and fluoro substitutes, the molecular-level control over the chemical environment surrounding a catalytic center could be readily achieved in our MOFs. To investigate the effects of these substitutes on catalytic activity and selectivity, the oxidation of 3-methylpentane to corresponding alcohols and ketones was utilized as a model reaction. Within these five analogues of PCN-224, an extremely high turnover number of 7680 and turnover frequency of 10 240 h–¹ was achieved by simply altering the substitutes on porphyrin rings. Moreover, a remarkable 99% selectivity of the tertiary alcohol over the five other possible by-products are realized. We demonstrate that this strategy can be used to efficiently screen a suitable peripheral environment around catalytic cores in MOFs for catalysis.