It is important to develop an efficient noble-metal-based catalyst that has a wide work temperature window and good stability for CO preferential oxidation in H 2 (CO-PROX), a key step to purify industrial hydrogen resource. Herein, a catalyst of Fe-substituted hexaaluminatesupported Ir nanoparticles with a mean size of ∼1.4 nm (Ir/BaFeAl 11 O 19 ) is synthesized. It can exhibit total CO conversion for the CO-PROX reaction in an unprecedented temperature range from 20 to 200 °C, high stability, and good resistance to CO 2 and H 2 O in a simulated practical atmosphere. Detailed characterizations coupled with density functional theory (DFT) calculations show that the interaction between Ir species and framework Fe cations in mirror planes of hexaaluminate promotes the formation of a certain amount (8%) of Fe 2+ species for low-temperature CO oxidation, while the Ir species interacting with these Fe 2+ provide moderate CO bond strength that is critical to maintaining the preferential oxidation of CO rather than H 2 at high temperatures.
All chemical reagents were obtained from commercial suppliers and used directly. The other organic solvents and inorganic reagents were purified by the standard anhydrous methods before use. TLC analysis was carried out using pre-coated glass plates. Column chromatography was done by using silica gel (200-300 mesh). NMR spectra were recorded in CDCl3 on a Bruker-ARX 400 instrument at 25 o C. Chemical shifts are reported in ppm with internal standard of tetramethylsilane (TMS). MS spectra were performed from Bruker MALDI-TOF mass spectrometer. The phase transitions were examined by POM (Leica DMRX) with a hot stage (Linkam THMSE 600). Thermal analysis was performed by DSC (Thermal Analysis Q100) at a scanning rate of 10 o C/min under N2 atmosphere. XRD experiments were done on SEIFERT-FPM (XRD7), using Cu Kα 1.5406Å as the radiation source with 40 kV, 30 mA power. UV-Vis were performed on Varian spectrometer. Fluorescence spectra were measured on a Hitachi F-4500 spectrometer equipped with excitation and emission slits 10nm wide. The fluorescence absolute ΦF values were obtained on an Edinburgh Instruments FLS920 Fluorescence Spectrometer with a 6-inch integrating sphere. Compound 1 was synthesized by the reported procedures (Tetrahedron Letters, 2015, 56(6), 866-870). Compounds 5, 6 and 7 were prepared according to the published literature (Dyes and Pigments 2016, 133, 387-394).
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