Copper(II)‐Doped ZIF‐8 as a Reusable and Size Selective Heterogeneous Catalyst for the Hydrogenation of Alkenes using Hydrazine Hydrate

Abstract

In recent years, synthesis of mixed-metal organic frameworks has received considerable attention due to their superior performance than with mono-metallic metal organic frameworks (MOFs). In the present manuscript, Cu 2 + ions are doped within the framework of ZIF-8 (ZIF: Zeolitic Imidazolate Frameworks) to obtain Cu@ZIF-8 and is characterized by powder X-ray diffraction (XRD), Fourier transform infrared (FT-IR), UV-Visible diffuse reflectance spectra (DRS), scanning electron microscope (SEM) and transmission electron microcope (TEM) studies. The reaction conditions are optimized with styrene as a model substrate using Cu@ZIF-8 as a solid catalyst. Heterogeneity of the reaction is confirmed by leaching test and the solid is reusable for three recycles with no diminishing activity. Further, the structural integrity of Cu@ZIF-8 is also retained after hydrogenation of styrene as evidenced by powder X-ray diffraction. The size selective catalysis of Cu@ZIF-8 is demonstrated by comparing the activity of Cu 2 + ions adsorbed over ZIF-8 solid (Cu/ZIF-8) in the hydrogenation of 1-hexene, 1octene, cyclohexene, cyclooctene and t-stilbene. The catalytic results indicate that Cu/ZIF-8 shows superior activity than Cu@ZIF-8 for all these olefins due to the lack of diffusion to access the active sites (Cu 2 + ). In contrast, Cu@ZIF-8 exhibits higher activity for those olefins with lower molecular dimensions (1-hexene, 1-octene) than the pores of ZIF-8 indicating the facile diffusion of these substrates inside the pores ZIF-8 while poor activity is observed with t-stilbene due to its larger molecular dimension than the pore apertures of ZIF-8. These catalytic data clearly establish the size selective hydrogenation of Cu@ZIF-8 due to the effective confinement provided by ZIF-8 framework and the presence of the active sites within the framework. Furthermore, this is the first report showing the size selective hydrogenation of olefins promoted by Cu@ZIF-8 (mixed-metal MOFs) compared to other noble metal nanoparticles (NPs) embedded over MOFs as catalysts.

Sustained Endogenous Nitric Oxide Catalytic System Endows Skin Scaffolds with Antibiofilm and Antibacterial Activities

“…The absorption peak at 423 cm –1 belonged to the Zn–N stretching mode, , indicating that Zn formed a ZIF coordination structure with the N atom on the 2-methylimidazole ligand. The stretching frequencies in the range of 1100–1300 cm –1 were related to the C–H vibration . The absorption peaks at 1466 and 1470 cm –1 and 1229 and 1231 cm –1 were the CN stretching vibration and the C–N vibrations on the imidazole ring, respectively .…”

“…The stretching frequencies in the range of 1100–1300 cm –1 were related to the C–H vibration . The absorption peaks at 1466 and 1470 cm –1 and 1229 and 1231 cm –1 were the CN stretching vibration and the C–N vibrations on the imidazole ring, respectively . The coexistence of C–N and CN indicated the presence of imidazole molecules.…”

Copper(II)-Doped Two-Dimensional Titanium-Based Metal–Organic Frameworks toward Light-Driven CO2Reduction to Value-Added Products

“…In general, the enhanced light absorption could be conducive to the improvement of the photocatalytic performance. It is documented that the DRS absorption band at around 600–1000 nm was usually caused by the d–d transition of Cu 2+ . − With the combination of the apparent color and DRS results of Cu 2+ -doped samples, a conclusion could be drawn that additional Cu ions were successfully introduced into the structure of the TM1 matrix in the form of positive divalent ions. In addition, the original DRS spectrum could be transformed into the corresponding Tauc plot by applying the conversion formula (α h ν) 1/ r = C ( h ν – E g ), where α, ν, and C represent the absorption coefficient, incident light frequency, and proportional constant, respectively, and the r value is 1/2 (direct semiconductors) or 2 (indirect semiconductors) .…”

Superoxide Dismutase‐like Activity of Zeolitic Imidazolate Framework Nanoparticles Comprising Biomimetic Imidazolato‐bridged CuZn Units

“…Schneider and colleagues first synthesized CuZn‐ZIF‐8 (also known as Cu‐doped ZIF‐8) and demonstrated its efficacy and reusability as a catalyst for [3+2] azide–alkyne cycloaddition [33] . Since then, CuZn‐ZIF‐8 has been utilized as catalysts for a wide range of reactions with redox‐active metal centers, including aerobic alkane oxidation [34] and alcohol, [35] β ‐ketosulfone synthesis from alkynes, [36] dehydrogenative coupling of silanes with alcohols, [37] and hydrogenation of alkenes, [38] and CO 2 reduction [39] …”