CuCo Nanoparticle, Pd(II), and l-Proline Trifunctionalized UiO-67 Catalyst for Three-Step Sequential Asymmetric Reactions

Abstract

Metal−organic frameworks (MOFs) have become a promising support for different active sites to construct multifunctional and heterogeneous catalysts. However, the related investigation mainly focuses on introducing one or two active sites into MOFs and trifunctional catalysts have been very rarely reported. Herein, non-noble CuCo alloy nanoparticles, Pd 2+ , and L-proline, as encapsulated active species, functional organic linkers, and active metal nodes, respectively, were successfully decorated to UiO-67 to construct a chiral trifunctional catalyst by the one-step method, which was further applied to asymmetric three-step sequential oxidation of aromatic alcohols/Suzuki coupling/asymmetric aldol reactions with excellent oxidation and coupling performance (yields up to 95 and 96%, respectively), as well as good enantioselectivities (ee anti value up to 73%) in asymmetric aldol reactions. The heterogeneous catalyst can be reused at least five times without obvious deactivation due to the strong interaction between the MOFs and the active sites. This work provides an effective strategy to construct multifunctional catalysts via the introduction and combination of three or more of active sites, including encapsulated active species, functional organic linkers, and active metal nodes, into stable MOFs.

Mechanistic Insights into a Co(II)-Coordinated “Free” Metal Site of 2D Zinc-Based MOFs for β-Alkylation of Secondary Alcohols with Primary Alcohols

“…Metal–organic framework (MOF)-based materials, especially for functional MOFs with unsaturated coordination metal sites and functional organic ligand, have long been a research hotspot in the field of catalysis due to unique properties. − Because the presence of unsaturated coordination metal sites in MOF structures enables the effective fixation of introduced metals onto the ligands, thereby enhancing the stability of the metal introduced in the catalyst preparation process and minimizing the loss of active components during the reaction. Moreover, of utmost importance is that MOF structures containing these unsaturated coordination sites can selectively coordinate with different active metals to prepare catalysts with varying activities for catalyzing different organic reactions. − This feature allows the prepared MOF materials with unsaturated coordination sites to serve as universal templates, simplifying the catalyst preparation process and ultimately improving the overall efficiency of the catalytic process. − Furthermore, this aligns with the current goal of achieving carbon neutrality. Therefore, the development of MOFs as carriers for the preparation of efficient catalysts supported by MOFs has become crucial in heterogeneous catalytic reactions …”

Improving the Bioactivity and Stability of Embedded Enzymes by Covalent Organic Frameworks

“…Immobilizing enzymes on solid supports is an effective strategy to enhance their stability, reusability, and easy operation, which are desired for the development of enzyme catalysts. − Due to the advantages of reticular chemistry materials (such as high porosity, stability, and tunability), metal–organic frameworks (MOFs) and covalent organic frameworks (COFs) have recently been regarded as excellent supports for enzyme immobilization. − To date, a series of MOFs, especially ZIFs, have been widely explored for de novo immobilizing enzymes; however, the bioactivity of immobilized enzymes is sometimes far from satisfactory, which is caused by the diffusion barriers of ZIFs (pore size of the commonly used ZIF-8: 0.34 nm) and the unavoidable activity loss during the immobilizing process, such as harmful metal ions. − Meanwhile, a lot of research has successfully enhanced the activity of the immobilized enzyme, such as modulating the microenvironment, shortening diffusion paths, and enabling biocatalytic cascades. − However, there is still an essential problem that has not been solved in enzyme@MOF biocomposites, which is the unavoidable influence of metal ions on enzymatic activity. Some reports have proved that metal ions can coordinate with enzymes, which may perturb their conformation or cover their active sites, leading to unpredictable changes in activity and even the complete inactivation of enzymes. − …”