Single-chain polymer nanoparticles-encapsulated chiral bifunctional metal-organic frameworks for asymmetric sequential reactions

Abstract

• Pd(II) was stably loaded in the channels of MOFs using Pd(II) cross-linked single-chain nanoparticles. • A bifunctional catalyst Pd-SCNP@DUT-67-Pro was prepared by the “one-pot” method. • The catalyst was used for Suzuki coupling/asymmetric aldol sequential reactions. • The catalyst can be used for 3 cycles without activity loss and structural changes. Among multitudinous development methods of the active sites of MOFs, the encapsulation method is widely used. However, metal ions with excellent catalytic performance are not suitable for being directly encapsulated in MOFs. Because metal ions are much smaller than the pore sizes of MOFs, they will move in and out of the channels of MOFs haphazardly rather than being stably loaded in the channels like that of enzymes and metal nanoparticles. Here, to solve the above-mentioned problem, the metal ion Pd(II) was introduced into the single-chain polymer nanoparticles (SCNP) to form Pd(II) cross-linked SCNP (Pd-SCNP). A bifunctional heterogeneous catalyst Pd-SCNP@DUT-67-Pro was prepared by introducing Pd-SCNP and chiral proline into the channels and on the Zr-clusters of DUT-67, respectively. The catalyst displayed excellent enantioselectivity and good coupling performance in Suzuki coupling/asymmetric aldol sequential reactions. Besides, Pd-SCNP@DUT-67-Pro still retained good catalytic activity within three cycles of reuse.