In this review we focus on the catalytic removal of a series of N-containing exhaust gases with various valences, including nitriles (HCN, CH3CN, and C2H3CN), ammonia (NH3), nitrous oxide (N2O), and nitric oxides (NO(x)), which can cause some serious environmental problems, such as acid rain, haze weather, global warming, and even death. The zeolite catalysts with high internal surface areas, uniform pore systems, considerable ion-exchange capabilities, and satisfactory thermal stabilities are herein addressed for the corresponding depollution processes. The sources and toxicities of these pollutants are introduced. The important physicochemical properties of zeolite catalysts, including shape selectivity, surface area, acidity, and redox ability, are described in detail. The catalytic combustion of nitriles and ammonia, the direct catalytic decomposition of N2O, and the selective catalytic reduction and direct catalytic decomposition of NO are systematically discussed, involving the catalytic behaviors as well as mechanism studies based on spectroscopic and kinetic approaches and molecular simulations. Finally, concluding remarks and perspectives are given. In the present work, emphasis is placed on the structure-performance relationship with an aim to design an ideal zeolite-based catalyst for the effective elimination of harmful N-containing compounds.

The mechanism on interfacial synergistic catalysis for supported metal catalysts has long been explored and investigated in several important heterogeneous catalytic processes (e.g., water-gas shift (WGS) reaction). The modulation of metal-support interactions imposes a substantial influence on activity and selectivity of catalytic reaction, as a result of the geometric/electronic structure of interfacial sites. Although great efforts have validated the key role of interfacial sites in WGS over metal catalysts supported on reducible oxides, direct evidence at the atomic level is lacking and the mechanism of interfacial synergistic catalysis is still ambiguous. Herein, Ni nanoparticles supported on TiO (denoted as Ni@TiO) were fabricated via a structure topotactic transformation of NiTi-layered double hydroxide (NiTi-LDHs) precursor, which showed excellent catalytic performance for WGS reaction. In situ microscopy was carried out to reveal the partially encapsulated structure of Ni@TiO catalyst. A combination study including in situ and operando EXAFS, in situ DRIFTS spectra combined with TPSR measurements substantiates a new redox mechanism based on interfacial synergistic catalysis. Notably, interfacial Ni species (electron-enriched Ni site) participates in the dissociation of HO molecule to generate H, accompanied by the oxidation of Ni-O -Ti (O : oxygen vacancy) to Ni-O-Ti structure. Density functional theory calculations further verify that the interfacial sites of Ni@TiO catalyst serve as the optimal active site with the lowest activation energy barrier (∼0.35 eV) for water dissociation. This work provides a fundamental understanding on interfacial synergistic catalysis toward WGS reaction, which is constructive for the rational design and fabrication of high activity heterogeneous catalysts.

The electronic metal–support interaction (EMSI) plays a crucial role in promoting catalytic performance toward interface electronic structure sensitive reactions, such as the low temperature water gas shift reaction (LT-WGSR). Herein, a mixed metal oxide support (ZnTi-MMO) was obtained via structural topological transformation from a zinc–titanium layered double hydroxides (ZnTi-LDHs) precursor, which was used for the immobilization of Au nanoparticles (NPs). Following a reduction pretreatment at 300 °C in a H2 atmosphere, the resulting optimal catalyst Au@TiO2–x /ZnO­(H300) exhibits a WGSR rate up to 0.15 molco molAu –1 s–1, which is at a high level compared with previously reported gold-based catalyst systems. Ac-HAADF-STEM combined with CO pulse chemisorption measurements verifies a TiO2–x overlayer on the surface of Au NPs. Quasi in situ XPS, EPR, in situ EXAFS, and in situ DRIFTS demonstrate the formation of interface dual-active-site (Auδ−–Ov–Ti3+; Ov: oxygen vacancy) based on electron transfer from the TiO2–x overlayer to Au atoms, in which the electron-enriched Auδ− species enhance CO chemisorption while Ov–Ti3+ accelerates the dissociation of the H2O molecule, accounting for the largely enhanced catalytic activity and stability of Au@TiO2–x /ZnO­(H300) compared with the traditional Au/TiO2 system. In situ/operando EXAFS further confirms that Auδ−–Ov–Ti3+ interfacial site serves as the optimal active site toward WGSR: both Auδ− species and Ov directly participate in the rate-determining step of LT-WGSR (water dissociation). The discovery and identification of the interfacial active site in this system can be extended to other metal catalysts with largely promoted performance in heterogeneous catalysis.

In this study, an economical way for SSZ-13 preparation with the essentially cheap choline chloride as template has been attempted. The as-synthesized SSZ-13 zeolite after ion exchange by copper nitrate solution exhibited a superior SCR performance (over 95% NOx conversion across a broad range from 150 to 400 °C) to the traditional zeolite-based catalysts of Cu-Beta and Cu-ZSM-5. Furthermore, the opportune size of pore opening (∼3.8 Å) made Cu-SSZ-13 exhibiting the best selectivity to N2 as well as satisfactory tolerance toward SO2 and C3H6 poisonings. The characterization (XRD, XPS, XRF, and H2-TPR) of samples confirmed that Cu-SSZ-13 possessed the most abundant Cu cations among three investigated Cu-zeolites; furthermore, either on the surface or in the bulk the ratio of Cu(+)/Cu(2+) ions for Cu-SSZ-13 is also the highest. New finding was announced that CHA-type topology is in favor of the formation of copper cations, especially generating much more Cu(+) ions than the others, rather than CuO. The activity test of Cu(CuCl)-ZSM-5 (prepared by a solid-state ion-exchange method) clearly indicated that Cu(+) ions could make a major contribution to the low-temperature deNOx activity. The activity of protonic zeolites (H-SSZ-13, H-Beta, H-ZSM-5) revealed the topology effect on SCR performances.

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