A series of self-assembled composites of POM with COF were constructed using a step-by-step one-pot thermal method. The composites were prepared using different precursor compositions, namely 1,4-Piperazinedicarboxaldehyde and 1-Formylpiperazine. Among the composites, POM@CIN-1 demonstrated the highest removal efficiency for DBT molecules, reaching 99 % at an oxygen-to-sulfur ratio of 5 and under mild conditions (60 degrees C). Furthermore, the composite exhibited excellent cycling stability. The characterization results demonstrated that the CIN-1 structure was more ordered and layered than that of CIN-2. Furthermore, the kinetic and thermodynamic analyses indicated that the POM@CIN-1 system exhibited a pseudo-secondary kinetic behavior and was well-represented by the Langmuir model. This suggests that the desulphurization mechanism may be a process of sulfide transfer by adsorption, in which chemisorption and physisorption coexist. Additionally, this study elucidates the underlying reasons for the discrepancies in sulfide removal rates from the vantage point of model structures and electron cloud densities, as revealed by DFT calculations. It also puts forth the concept of modulating the catalytic efficiency of ODS through the design of the LUMO and reaction path of the catalysts. Meanwhile, the intrinsic mechanism of the ODS reaction was elucidated in detail with regard to the elementary reaction steps and the electron transfer mechanism. Finally, a "Soil-Plant-Root" model was constructed with the aim of demonstrating the underlying principles and mechanisms of catalytic oxidative desulfurization in a more intuitive and vivid manner. It is anticipated that this work will provide new insights and avenues for the advancement of ultra-deep fuel desulfurization and the industrial implementation of ODS in the future.

The rubidium barium polyphosphate RbBa2(PO3)5 containing impurity bismuth monocations has been prepared via crystallization from a melt with the stoichiometric composition and melts containing excess of rubidium or barium. The samples thus obtained demonstrate broadband photoluminescence in the Near-IR. Analysis of their photoluminescence properties leads us to conclude that they contain two types of emission centers and that predominant formation of one of them depends on melt composition. Our results show that one of the emissive centers is a bismuth monocation substituting for a barium cation and that it forms mainly from barium-deficient melts. The other emissive center, a Bi+ monocation substituting on the rubidium site, results predominantly from crystallization of rubidium-deficient melts.

Catalysts based on high-silica zeolites with Si/Al ratios of 50 and 80 (ZSM-5-50 and ZSM-5-80) modified by Ca, Sr, Cr, Mn, and Sb ions are synthesized and studied in the reaction of the oxidation of benzene to phenol by nitrous oxide. It is shown that catalysts containing about 0.1–0.2 wt

We were able to observe an intense, broadband photoluminescence in different crystal hosts, doped with $\mathrm {C u}^{2+}$. These matrices include corundum (alpha-Al 2 O 3 ), different spinels: $\mathrm {M g A l}_{2} \mathrm{O}_{4}, \mathrm{MgGa}_{2} \mathrm{O}_{4}, \mathrm{ZnAl}_{2} \mathrm{O}_{4}, \mathrm{ZnGa}_{2} \mathrm{O}_{4}$, spinel-like compounds $\mathrm{LiAl}_{5} \mathrm{O}_{8}, \mathrm{LiGa}_{5} \mathrm{O}_{8}$, perovskites $\mathrm{LaAlO}_{3}, \mathrm{GdAlO}_{3}$. The main common feature of these materials is the large magnitude of the crystal field, which contributes to the appearance of photoluminescence. Otherwise, the strong electron-phonon coupling in the ground state due to the manifestation of the Jahn-Teller effect can lead to photoluminescence quenching due to the high rate of non-radiative relaxation. It has also been demonstrated that codoping with divalent ions dramatically enhances the photoluminescence of copper in corundum and perovskites.

— We have studied broadband (1000–1600 nm) IR photoluminescence of polycrystalline corundum (α-Al 2 O 3 ) samples containing copper impurity ions and additionally doped with ions of elements in the oxidation state 4+: Si 4+ , Ge 4+ , Ti 4+ , Zr 4+ , Hf 4+ , and Sn 4+ . The results demonstrate that the IR photoluminescence intensity in corundum singly doped with copper is rather low. Additional doping of corundum with some tetravalent cations sharply increases the luminescence intensity. The largest increase in Cu 2+ IR photoluminescence intensity is obtained in the case of additional doping with Ti 4+ , Ge 4+ , or Sn 4+ cations. It seems likely that these ions ensure charge compensation when incorporated into the corundum lattice together with Cu 2+ ions, so that the substitution process can be represented as 2Al 3+ → Cu 2+ + M 4+ (M 4+ = Ti 4+ , Ge 4+ , Sn 4+ ,…). In this way, the additional doping of corundum with tetravalent ions raises Cu 2+ solubility in α-Al 2 O 3 , leading to photoluminescence enhancement in the material.

The occurrence of dry reforming of methane (DRM) in a steady-state mode and partial oxidation of methane (POM) in a self-oscillating mode over a nickel foil sample and the simultaneous occurrence of these two reactions have been studied. It has been shown that during the cooccurrence of the DRM and POM reactions, a kinetic coupling of these reactions takes place; it is evident as a change in the self-oscillation period and a significant acceleration of the DRM reaction in certain phases of the self-oscillation cycle compared with the DRM rate over this Ni sample in a steady-state mode. The DRM acceleration effect is observed in a temperature range of 600–750°C. The maximum increase in the CO2 conversion value averaged over the oscillation period is a factor of 2.6 at a temperature of 700°C for a feed gas mixture composition of CH4 : CO2 = 1 : 1 + 3.5

Catalytic activity of Co foil in ethylene oxidation was studied against oxidation degree of Co surface at stepwise foil oxidation. Experiments were conducted at temperatures of 500–800°C by a pulse method using alternative pulses of 0.2% C2H4–0.25% O2–1% Ar–He testing mixture and 1% O2–1% Ar–He oxidative mixture. Oxidation degree of Co foil varied from a totally reduced surface to an oxidation depth about a hundred of cobalt oxide “monolayers”. Using XRD, SEM and EDS, it was shown that CoO phase formed during a first stage of the stepwise oxidation (from 0 to ~60 oxide “monolayers”) at the all tested temperatures and modifications of surface morphology could be observed. At this stage the samples had a relatively high activity in both partial and total oxidation of ethylene at 500–600°C. On the contrary, at 700–800°C total oxidation was practically absent and the rate of partial oxidation was much lower than that at 500–600°C. During a second stage of Co surface oxidation (from ~60 to ~120 oxide “monolayers”) at 500–600°C also Co3O4 phase was found as well as a gradual ordering of the oxide crystals. In that state, the samples demonstrated a stationary (at 500°C) or an extremal (at 600°C) activity in total oxidation of ethylene. On the contrary, a temperature increase up to 800°C led to a sharp decrease of catalytic activity of the Co foil in this interval of oxidation degree.

Кристаллизацией из расплава получены образцы полифосфата рубидия-бария RbBa 2 (PO 3 ) 5 , содержащего примесные монокатионы висмута. Использовался расплав стехиометрического состава, а также расплавы с избытком рубидия или бария. Образцы демонстрируют широкополосную фотолюминесценцию в ближнем ИК-диапазоне. На основании анализа фотолюминесценции образцов сделан вывод о наличии в них двух типов излучающих центров, преимущественное образование которых зависит от состава расплава. Показано, что один из люминесцентных центров представляет собой монокатион висмута, замещающий катион бария, причем он в основном образуется из расплавов, обедненных барием. Второй люминесцентный центр, представляющий собой монокатион Bi + в положении рубидия, образуется преимущественно при кристаллизации расплавов, обедненных рубидием.

— The rubidium barium polyphosphate RbBa 2 (PO 3 ) 5 containing impurity bismuth monocations has been prepared via crystallization from a melt with the stoichiometric composition and melts containing excess of rubidium or barium. The samples thus obtained demonstrate broadband photoluminescence in the Near-IR. Analysis of their photoluminescence properties leads us to conclude that they contain two types of emission centers and that predominant formation of one of them depends on melt composition. Our results show that one of the emissive centers is a bismuth monocation substituting for a barium cation and that it forms mainly from barium-deficient melts. The other emissive center, a Bi + monocation substituting on the rubidium site, results predominantly from crystallization of rubidium-deficient melts.

Polycrystalline samples of the mixed cyclotriphosphates KMgP3O9, KCaP3O9, RbMgP3O9, RbCaP3O9, CsCaP3O9, and CsSrP3O9 containing Bi+ bismuth impurity monocations have been prepared via crystallization from a melt of appropriate composition. The presence of Bi+ is responsible for broadband bright near-IR luminescence in all of the materials. The shape of the photoluminescence and photoluminescence excitation spectra has been shown to be determined by the nature of the alkaline earth cation in the composition in the cyclotriphosphates and the symmetry of the local environment of the Bi+ ions under the assumption that they isomorphously substitute for alkali metal cations in the crystal lattice of the cyclotriphosphates. The characteristic photoluminescence decay time is also determined by the symmetry of the local environment of Bi+.

Self-oscillatory reactions of ethane oxidation (I) or CO oxidation (II) over Co foil at a temperature of 620 or 660°C, respectively, for 1 h caused the formation of a microporous surface layer composed of CoO crystals with sizes of 0.2–0.4 μm. In reaction (I), the crystals formed agglomerates with a size of ~1 μm with pores of the same size between them. The thickness of the microporous layer after type I treatment was ~0.7 μm. On the contrary, the agglomerates and pores were almost absent after type II treatment. The catalytic activity of foil samples with the microporous surface layers in the reactions of deep ethylene oxidation, CO oxidation, and CO methanation was measured. It was found that a maximal increase in the catalytic activity took place after type I treatment. The stability of the resulting porous layers in an inert (He), reducing (H2), or oxidizing (O2) atmosphere was studied upon heating to 750°C. A significant recrystallization and cracking of the layer were observed upon the inert-gas treatment. After heating in hydrogen, a strongly fixed surface layer with stable catalytic activity was formed. Finally, as a result of heating in an oxidizing atmosphere, the thickness of the surface layer increased to 6–8 µm; the main component was Co3O4, and its catalytic activity was minimal among the three cases.

The paper is devoted to the experimental and theoretical studies of self-sustained oscillations and wave phenomena during CO oxidation on Ni foil. A new type of spatial structures arising due to the redox processes of the catalyst and observed under isothermal conditions at atmospheric pressure were studied. A 3D distributed mathematical model was constructed, which describes the color change and the propagation of kinetic waves of nickel oxidation–reduction in a flow-through reactor. The main reason for the wave phenomena and their propagation during CO oxidation on nickel was shown to be the presence of an oxygen concentration gradient in the flow-through reactor due to the effect of mass transfer on the reaction rate.

Low valence bismuth cationic centers were introduced into hydrogen forms of ZSM-5 and mordenite zeolites via impregnation of zeolites in aqueous solution of bismuth salts and subsequent reductive solid state ion exchange (SSIE). It has been found that Near IR photoluminescent bismuth monocations Bi+ and cluster ions are formed in the exchange positions and their optical properties in ZSM-5 and mordenite depend mainly on a zeolite Si/Al ratio and, to a lesser extent, on the amount of loaded bismuth. The photoluminescence emission and excitation spectra of bismuth cationic species (monocations or clusters) are markedly different in ZSM-5 and mordenite. This difference can be explained, taking into the account, that extraframework (exchanged) cations in mordenite zeolite, unlike ZSM-5, can occupy only several distinct positions relative to the mordenite framework structure.

Samples of (0.5–15)%CoO/CeO2, Co3O4, and CeO2 have been studied in the oxidation of CO to CO2 in a CO+O2+H2 mixture in a range of 40–340°C. The highest activity in CO oxidation is exhibited by 10%CoO/CeO2 with a characteristic conversion of CO to CO2 of γ50 = 50% at Т50 ≈ 140°С and γ ≈ 100% at Т = 180–220°С. The СО2 yield decreases at 220–240°C due to competition for oxygen in the CO and H2 oxidation reactions; at Т > 240°C, it decreases due to the consumption of CO in the methanation reaction. According to XRD and H2-TPR, cobalt oxide in the 10%CoO/CeO2 sample is present in two forms of a highly dispersed Co3O4 oxide (CoxOy clusters) interacting with the support and in the form of a Co3O4 phase. Carbon monoxide oxidation in a range of 60–180°C occurs on CoxOy clusters. Under these conditions, the activity of particles of the Co3O4 phase in pure oxide and the 10%CoO/CeO2 catalyst is lower than that of the clusters. The effect of the properties of adsorption complexes formed involving the oxygen contained in the clusters and in the gas phase on the temperature dependence of CO conversion has been studied.

The self-oscillatory mode of methane oxidation over Pd foil at temperature of 400°C for 1 h caused the formation of a surface layer containing bulky porous agglomerates of nanocrystals. According to SEM data, the agglomerates with diameters of 1–20 μm consisted of crystals ~100 nm in size with pores of similar sizes between them. The agglomerates projected over the surface by 5–10 μm. The catalytic activity of the treated samples in a CO oxidation reaction was measured. The temperature of the onset of the catalytic reaction (CO conversion, 3%) decreased from 400°C for the initial Pd foil to 200°C for the Pd foil after the self-oscillatory oxidation of methane. Results of X-ray diffraction analysis and energy-dispersive X-ray spectroscopy (EDS) allowed us to conclude that the agglomerates observed consisted of the crystals of palladium oxide (PdO). On the contrary, the oxidation of Pd foil surface in a stationary mode was found to promote the formation of a smooth layer of palladium oxide without noticeable porous structures, and the catalytic activity of this layer was lower than that of the Pd sample after self-oscillations. The stability of the obtained porous layers in an inert (He), reducing (H2), or oxidative (air) atmosphere on heating to 700°C was studied. Under the inert or reducing conditions, both the disappearance of palladium oxide and the destruction of nanoparticle agglomerates took place to cause a decrease in the catalytic activity of Pd foil in the CO oxidation reaction. On the contrary, the oxidative treatment caused both an increase in the PdO content of the sample and a growth of the number of porous nanocrystal agglomerates on the surface to result in an additional increase in the catalytic activity of Pd foil.

Polycrystalline samples of rubidium magnesium cyclotriphosphate RbMgP3O9 phase were prepared by crystallization from the melt. It was shown, that reductive conditions throughout crystallization process lead to the appearance of strong photoluminescence in the Near-IR. The photoluminescence spectrum contains the single band with maximum at 913 nm (300 K), while photoluminescence excitation spectrum consists of five bands in visible spectral diapason. The kinetic of photoluminescence decay after the pulse excitation can be fitted by single exponent with characteristic lifetime 525 mu s (300 K). We suppose, that univalent bismuth cation Bi+, substituted for Rb+, is the single Near-IR emissive center in RbMgP3O9 phase. This material and the similar bismuth-doped cyclotriphosphate phases can be the new optical materials with potential applications in photonics and laser physics.