Multifunction magnetic chiral MOF composite: A novel post-synthetic super catalyst for enhancing the asymmetric CO2 fixation

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Here in, a novel neutral Chiral Metal−Organic Framework (CMOF) composite, Cu(II)-l-proline/TCT/APTES/Fe3O4/MIL-101(Fe) (Cu(II)-HPro/TCT/APTES/Fe3O4/MIL-101(Fe)), has been derived from the chiral Cu(II)-l-proline complex (Cu(II)-HPro) attached to TCT/APTES/Fe3O4 and MIL-101(Fe). Achiral MIL-101(Fe) was chiralized by the incorporation of chiral Cu(II)-HPro complex anchored to TCT/APTES/Fe3O4 using ultrasonic-assisted electrostatic self-assembly technique (postsynthetic modification). The resulted super catalyst has chiral species acting as Lewis base sites, together with two active metal sites (Fe and Cu) acting as Lewis acid centers leading to multifunctionality. Due to chiral auxiliary Lewis bases and Lewis acids, the catalytic activity of the Cu(II)-HPro/TCT/APTES/Fe3O4/MIL-101(Fe) composite was evaluated in asymmetric catalysis of prochiral substrates. This asymmetric super catalyst has proved to be highly active in CO2 fixation reaction at ambient pressure, low-temperature, solvent-free medium with high conversion and enantioselectivity. Based on the results, enantiomeric excess (ee) [97 % (S)], carbonate selectivity (>99 %), and conversion (>99 %) all demonstrate the superior performance of the investigated catalytic system. Furthermore, the magnetic characteristic, together with excellent structure stability, leads to high recyclability for 7 runs without a significant reduction of catalytic activity. The outcomes showed that chiralization of MIL-101(Fe) could occur through a simple and green approach, which may be a practical way to create chiral multifunctionalized metal−organic frameworks (MOFs).