Chiral MOF catalysts via post-synthetic functionalization: Cu(II)-amino acid complex on MIL-101(Fe) for CO2 cycloaddition

The catalytic conversion of carbon dioxide (CO₂) into value-added chemicals under mild and sustainable conditions, particularly with high stereocontrol, remains a key challenge in green chemistry. Herein, we report the design and synthesis of a novel chiral hybrid catalyst through post-synthetic functionalization of the amine-tagged metal-organic framework NH₂-MIL-101(Fe) with a Cu(II)-hydroxy- L -proline complex. The stereoselective Cu(hydroxy- L -proline)₂ moiety was covalently anchored to the pendant amine groups via an ethylene linker, affording a well-dispersed chiral active site within the highly porous and recyclable MOF framework. The resulting material, MIL-101(Fe)-NH-(CH₂)₂-Cu(hydroxy- L -proline)₂, was comprehensively characterized by FT-IR, PXRD, BET, FE-SEM, TEM, XPS, TGA, EDX, ICP, and CD, confirming successful immobilization while preserving the crystallinity and porosity of the parent MOF. In the asymmetric cycloaddition of CO₂ to a series of representative epoxides, the catalyst exhibited excellent performance under mild conditions (1 atm CO₂, 80 °C, solvent-free), delivering chiral cyclic carbonates in up to 99% conversion and 99% enantiomeric excess ( ee ). Moreover, the heterogeneous catalyst could be easily recovered and reused for at least five cycles without significant loss of activity or selectivity. This work presents an effective strategy for constructing MOF-based asymmetric catalysts by integrating well-defined chiral metal complexes, offering a promising platform for the stereoselective fixation of CO₂ into valuable cyclic carbonates and advancing sustainable carbon utilization.