Chiral Proline-Decorated Bifunctional Pd@NH₂-UiO-66 Catalysts for Efficient Sequential Suzuki Coupling/Asymmetric Aldol Reactions

Abstract

The design and development of site-isolating and multifunctional catalysts for multistep sequential reactions at the molecular level is a significant challenge. Herein, we first report bifunctional metal NPs@chiral MOFs catalysts for asymmetric sequential reactions. Pd nanoparticles and chiral proline were successfully added to NH 2 -UiO-66 to construct two chiral bifunctional catalysts, in which active Pd nanoparticles were encapsulated into the frameworks via the "bottle-around-ship" method, and chiral proline was introduced into NH 2 -UiO-66 by coordination to zirconium nodes and postsynthetic modification (PSM) of the organic linkers. The chiral proline-decorated bifunctional Pd@NH 2 -UiO-66 catalysts were applied to sequential Suzuki coupling/asymmetric aldol reactions with excellent coupling performance (yields up to 99.9%) and good enantioselectivities (ee anti values up to 97%). The heterogeneous catalyst by coordination of proline can be reused, and the reaction activity was not significantly reduced after four cycles.

Palladium‐Based Metal Organic Frameworks as Heterogeneous Catalysts for C−C Couplings

“…Recently, a bifunctional heterogeneous catalyst was prepared consisting of Pd NPs and chiral proline on NH 2 ‐UiO‐66 solid to obtain Pd@NH 2 ‐UiO‐66(pro)‐1 solid catalyst (Figure 11). [93] Pd NPs were encapsulated inside the framework of NH 2 ‐UiO‐66 by employing the “bottle‐around‐ship” method, while chiral proline was decorated to the zirconium nodes and the organic linkers via coordination and PSM, respectively. The catalytic activity of Pd@NH 2 ‐UiO‐66(pro)‐1 was checked in the Suzuki‐Miyaura coupling of 4‐bromobenzaldehyde and phenylboronic acid using K 2 CO 3 as a base in EtOH/H 2 O (1 : 1) mixture at 80 °C after 10 min with quantitative yield of 4‐formylbiphenyl.…”

Rational Functionalization of UiO-66 with Pd Nanoparticles: Synthesis and In Situ Fourier-Transform Infrared Monitoring

“…Industrial catalytic reactions require high stability and porosity of support materials. The UiO MOF family is characterized by strong covalent Zr–O bonds and highly coordinated clusters resulting in exceptional stability of the material. − Various functionalization strategies have been applied to demonstrate the importance of the uniform distribution of NPs inside MOFs for catalytic applications. , Strong reduction agents such as NaBH 4 often lead to the formation of Pd NPs on the surface of UiO-66 crystals . Reduction in a hydrogen flow favored the formation of Pd NPs about 2–3 nm inside the UiO-66 matrix, although larger particles were still observed on the surface .…”

“…16−18 Various functionalization strategies have been applied to demonstrate the importance of the uniform distribution of NPs inside MOFs for catalytic applications. 19,20 Strong reduction agents such as NaBH 4 often lead to the formation of Pd NPs on the surface of UiO-66 crystals. 21 Reduction in a hydrogen flow favored the formation of Pd NPs about 2−3 nm inside the UiO-66 matrix, although larger particles were still observed on the surface.…”

Ni2P NPs loaded on methylthio-functionalized UiO-66 for boosting visible-light-driven photocatalytic H2production

“…24 Different modified functional groups of BDC organic links 25,26 can be modified to regulate the properties of UiO-66. 27 In recent years, BDC linkage agents have been functionalized with a variety of substituents, including -NH 2 , -OH, -SH, -SCH 3 , [28][29][30][31] and halogen atoms, to construct functionalized UiO-66-X compounds. 32 The band structure and light sensitivity of UiO-66 are significantly affected by the BDC ligand modification.…”