An effective strategy for creating asymmetric MOFs for chirality induction: a chiral Zr-based MOF for enantioselective epoxidation

• Published in: Catalysis science & technology 2019, Vol.9 (13), p.3388-3397
• Main Authors: Berijani, Kayhaneh, Morsali, Ali, Hupp, Joseph T
• Format: Article
• Language: English
• Subjects: Asymmetry; Catalysis; Catalysts; Chirality; Enantiomers; Epoxidation; Lewis acid; Metal-organic frameworks; Molybdenum oxides; NMR; Nuclear magnetic resonance; Oxidation; Pore size distribution; Porosity; Selectivity; Styrenes; Synthesis; Tartaric acid; Zirconium
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/c9cy00565j

Recently the construction of chiral MOFs (CMOFs) has been very challenging and complex. For the first time, we synthesized a chiral Zr-based MOF with l -tartaric acid by solvent-assisted ligand incorporation (SALI). We show that a CMOF can be postsynthetically generated by a simple method: incorporating chiral carboxylic groups on the achiral NU-1000. The post-synthesized chiral NU-1000 was used as an asymmetric support for producing a chiral catalyst with molybdenum catalytic active centers as Lewis acid sites. Enantioselective epoxidation of various prochiral alkens to epoxids by using [C-NU-1000-Mo] is comparable to that using other asymmetric homogeneous and heterogeneous catalysts, along with high enantiomeric excess and selectivity to epoxide (up to 100%). The CMOF could be reused in the styrene oxidation after five cycles without substantial deterioration in the CMOF crystallinity or catalytic performance. A simple and rapid procedure was used to prepare chiral NU-1000 as a robust Zr-based MOF without complexity. The functionalization of NU-1000 was performed by utilizing chiral l -(+)-tartaric acid via solvent-assisted linker incorporation, resulting in [C-NU-1000]. A Mo-complex was immobilized onto chiral NU-1000 for enantioselective epoxidation.