Highly Stable Chiral Zirconium-Metallosalen Frameworks for CO2 Conversion and Asymmetric C-H Azidation.

The engineering of highly stable metal-organic frameworks (MOFs) will unveil the intrinsic potential of these materials for practical applications, especially for heterogeneous catalyzes. However, it is fairly challenging to rationally design robust MOFs serving as highly effective and reusable heterogeneous catalysts. Here, for the first time, we report the construction of four robust UiO-type chiral zirconium-metallosalen frameworks, denoted ZSF-1-4. Single-crystal X-ray-diffraction reveals that the frameworks consist of twelve-connected Zr6O8 clusters with privileged chiral metallosalen ligands anchored at ideal positions, generating confined chiral cages that enable synergistic activation. Unlike UiO-68 that is highly sensitive to aqueous solutions, ZSF-1-4 exhibit excellent chemical stability in aqueous solutions with a wide range of pH owing to the abundant hydrophobic groups within metallosalen ligands. These features render ZSF-1 and ZSF-2 to be excellent recycled heterogeneous catalysts for the conversion of imitated industrial CO2 with epoxides into cyclic carbonates with the highest reported turnover numbers in Zr-MOFs. With regard to asymmetric catalysis, ZSF-3 and ZSF-4 can effectively catalyze C-H azidation reaction in water medium with ee value up to 94%. Moreover, these robust ZSFs can be further extended to other analogues with various metal centers through demetallization-remetallization strategy, which renders them to be an excellent platform for broader fields.