A facile approach was successfully developed for synthesis of cellulose nanocrystals (CNC)-supported magnetic CuFe2O4@Ag@ZIF-8 nanospheres which consist of a paramagnetic CuFe2O4@Ag core and porous ZIF-8 shell. The CuFe2O4nanoparticles (NPs) were first prepared in the presence of CNC and dispersant. Ag NPs were then deposited on the CuFe2O4/CNC composites via an in situ reduction directed by dopamine polymerization (PDA). The CuFe2O4/CNC@Ag@ZIF-8 nanocomposite was characterized by TEM, FTIR, XRD, N2adsorption-desorption isotherms, VSM, and XPS. Catalytic studies showed that the CuFe2O4/CNC@Ag@ZIF-8 catalyst had much higher catalytic activity than CuFe2O4@Ag catalyst with the rate constant of 0.64 min−1. Because of the integration of ZIF-8 with CuFe2O4/CNC@Ag that combines the advantaged of each component, the nanocomposites were demonstrated to have an enhanced catalytic activity in heterogeneous catalysis. Therefore, these results demonstrate a new method for the fabrication of CNC-supported magnetic core-shell catalysts, which display great potential for application in biocatalysis and environmental chemistry.Keywords:CuFe2O4nanoparticles;cellulose nanocrystals;Ag nanoparticles;ZIF-8 catalysis;4-nitrophenol reduction
Zhen-Hong He,Yuan-Yuan Wei,Na Li,Yong-Chang Sun,Shao-Yan Yang,Kuan Wang,Weitao Wang,Xiaoxue Ma,Zhao-Tie Liu
Chemical utilization of CO2 is one of the fundamental strategies to synthesize value-added chemicals and reduce the CO2 emission. N-formyl-1,2,3,4-tetrahydroisoquinoline derivatives (FTHIQs) are important chemicals for the synthesis of medical intermediates and alkaloids. N-formylation of isoquinoline derivatives (IQs) with CO2 is an ideal protocol to synthesize the FTHIQs and utilize the CO2 source. In the present work, we prepared a heterogeneous Ru/ZIF-8 catalyst with a Ru loading of 2 wt% by a simple impregnation method and assessed its performances in the N-formylation of IQs and CO2 with H2. The Ru/ZIF-8 catalyst offered high IQ conversion of 98% and FTHIQ selectivity of 93% in the reaction under relatively mild conditions (150 °C, 2 MPa CO2, and 6 MPa H2). The catalyst possessed good universality and reusability, showing a potential in wide application of N-formylation of highly unsaturated nitrogen-containing isoquinolines.
Zeolitic imidazolate framework-8 (ZIF-8) based catalysts are considered as promising candidates for the selective catalytic reduction of NO by CO (CO-SCR) reaction due to their large specific surface area. However, the structure of ZIF-8 will be damaged during the synthesis procedure of the catalyst, leading to a decrease in their physical properties, which in turn affects the catalytic performance of the catalyst. Herein, a CeO 2 -ZIF-8 core-shell structure was synthesized and doped with Fe, resulting in the formation of Fe@CeO 2 -ZIF-8, for CO-SCR reaction. Characterization results show that the Fe@CeO 2 -ZIF-8 core-shell catalyst has better morphology, thermal stability, and higher specific surface area than the FeCe co-impregnated ZIF-8 catalyst (FeCe@ZIF-8 (IM)). Moreover, the reducibility of the reactive Fe species in the Fe@CeO 2 -ZIF-8 core-shell catalyst is also enhanced. As a result, the Fe@CeO 2 -ZIF-8 core-shell catalyst exhibited higher low-temperature CO-SCR catalytic activity with its NO conversion reaching 99% at 250 °C versus the FeCe@ZIF-8 (IM) catalyst (89% at 250 °C). The experimental results were further verified by density functional theory (DFT) calculations including Electron Localization Function (ELF), Valence Charge Density Difference (VCDD), Projected Density of States (PDOS) and Bader charge analyses. The calculation results revealed that the core-shell configured Fe@CeO 2 -ZIF-8 catalyst has a stronger active metal-support charge transfer and better capacity for the adsorption of the reactants. The reaction mechanism over Fe@CeO 2 -ZIF-8 core-shell catalyst was investigated via in situ DRIFTS experiments, and results showed that the nitro compounds and formate species are critical intermediates in this reaction at a higher temperature range (300–350 °C). This work provides a new strategy for the synthesis of ZIF-8 based catalysts with better properties for CO-SCR reaction.
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