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The hydroamination of alkynes is an atom-economy process in the organic synthesis for the C-N bond formation, thereby allowing the production of fine chemicals and intermediates. However, direct interaction between alkynes and amines is complicated due to the electron enrichment of both compounds. Therefore, efficient hydroamination catalysts, especially heterogeneous ones, are in great demand. This work aimed at the development of novel heterogeneous catalysts based on zeolite-like metal-organic frameworks for phenylacetylene hydroamination. The sodalite (SOD) type zeolitic imidazolate framework ZIF-67 (Co(meim) 2 , meim = 2-methylimidazolate) and boron imidazolate framework BIF-66 ({Co[B(im) 4 ] 2 } n , im = imidazolate) were studied as the carriers for the gold nanoparticles (Au-NPs). Au-NPs were embedded in the ZIF-67 and BIF-66 matrices by incipient wetness impregnation. Au@ZIF-67 and Au@BIF-66 hybrids were studied for the first time in the liquid phase hydroamination of phenylacetylene with aniline in an air atmosphere and have shown high activity and selectivity in respect to imine in this process. The pronounced impact of the nature of the metal-organic carrier, Au source, and reducing agent on the catalytic performance of the synthesized nanomaterials was found. To the best of our knowledge, it is the first example of using the zeolitic imidazolate framework and boron-imidazolate framework as the components of the gold-containing catalytic systems for the alkyne hydroamination.

Here, we report the structures and properties of biocatalysts based on glucose oxidase (GOx) macromolecules immobilized on the mesoporous zirconia surface with or without magnetic iron oxide nanoparticles (IONPs) in zirconia pores. Properties of these biocatalysts were studied in oxidation of d-glucose to d-gluconic acid at a wide range of pH and temperatures. We demonstrate that the calcination temperature (300, 400, or 600 °C) of zirconia determines its structure, with crystalline materials obtained at 400 and 600 °C. This, in turn, influences the catalytic behavior of immobilized GOx, which was tentatively assigned to the preservation of GOx conformation on the crystalline support surface. IONPs significantly enhance the biocatalyst activity due to synergy with the enzyme. At the same time, neither support porosity nor acidity/basicity shows correlations with the properties of this biocatalyst. The highest relative activity of 98% (of native GOx) at a pH 6-7 and temperature of 40-45 °C was achieved for the biocatalyst based on ZrO 2 calcined at 600 °C and containing IONPs. This process is green as it is characterized by a high atom economy due to the formation of a single product with high selectivity and conversion and minimization of waste due to magnetic separation of the catalyst from an aqueous solution. These and an exceptional stability of this catalyst in 10 consecutive reactions (7% relative activity loss) make it favorable for practical applications., Competing Interests: The authors declare no competing financial interest., (Copyright © 2020 American Chemical Society.)

Here, we report on the development of novel Zn-, Zn-Cr-, and Zn-Cu-containing catalysts using magnetic silica (Fe 3 O 4 -SiO 2 ) as the support. Transmission electron microscopy, powder X-ray diffraction, and X-ray photoelectron spectroscopy (XPS) showed that the iron oxide nanoparticles are located in mesoporous silica pores and the magnetite (spinel) structure remains virtually unchanged despite the incorporation of Zn and Cr. According to XPS data, the Zn and Cr species are intermixed within the magnetite structure. In the case of the Zn-Cu-containing catalysts, a separate Cu 2 O phase was also observed along with the spinel structure. The catalytic activity of these catalysts was tested in methanol synthesis from syngas (CO + H 2 ). The catalytic experiments showed an improved catalytic performance of Zn- and Zn-Cr-containing magnetic silicas compared to that of the ZnO-SiO 2 catalyst. The best catalytic activity was obtained for the Zn-Cr-containing magnetic catalyst prepared with 1 wt % Zn and Cr each. X-ray absorption spectroscopy demonstrated the presence of oxygen vacancies near Fe and Zn in Zn-containing, and even more in Zn-Cr-containing, magnetic silica (including oxygen vacancies near Cr ions), revealing a correlation between the catalytic properties and oxygen vacancies. The easy magnetic recovery, robust synthetic procedure, and high catalytic activity make these catalysts promising for practical applications.

The reduction of Cu(II) oxide species in siliceous matrixes of different porosity (MFI, FAU, MCM-48) and in alumosilicate MFI was studied by temperature-programmed reduction in hydrogen (TPR), by X-ray absorption fine structure (after stationary hydrogen treatments), and by transmission electron microscopy. It was found that the reduction may proceed in one or in two reduction steps. The two-step scheme known for zeolites was observed also for Cu(II) in siliceous microporous matrixes, with similar temperature of Cu(II) reduction onset as for the alumosilicate MFI. Therefore, the two-step scheme cannot be explained by the stabilization of Cu ions by intra-zeolite electrical fields. CuOx clusters in MCM-48 were reduced in a one-step scheme (similar to bulk CuO) at high Cu content (6 wt %) but in a two-step scheme at low Cu content (1 wt %). The two reduction steps observed with most samples cannot be identified with the transitions of all Cu(II) to Cu(I) and of Cu(I) to Cu(0). Instead, Cu(0) nuclei were observed already at low reduction temperatures and were found to coexist with Cu ions over temperature ranges of different extension. This coexistence range was narrow in materials that favor aggregation of the Cu nuclei into particles: Cu-MCM-48 of low Cu content and Cu-ZSM-5. In the latter, metal segregation from the pore system was found to be accompanied by an autocatalytic initiation of the second reduction step. In the siliceous microporous matrixes, the Cu(0) nuclei were observed to coexist with Cu ions over wide temperature ranges (100 K for MFI) at temperatures far above that of Cu reduction in the bulk oxide. These observations suggest that oligomeric Cu metal nuclei which may have been formed, e.g., at the intersections of the MFI channel system, may be unable to activate hydrogen, which would be required for rapid reduction of the coexisting Cu ions.