Syntheses and crystal structures of four lanthanide complexes based on two tri-protonated hexacarboxylic acids of 1,2,3,4,5,6-cyclohexane-hexacarboxylic acid and mellitic acid

<div><p>Four lanthanide complexes with two tri-protonated hexacarboxylic acids [1,2,3,4,5,6-cyclohexane-hexacarboxylic acid (H₆chhc) and mellitic acid (H₆Mel)], [Pr(H₃chhc)(DMF)₃(H₂O)]·H₂O (<b>1</b>), Nd(H₃chhc)(DMF)₃ (<b>2</b>), [Er(H₂O)₈]·(H₃Mel)·9(H₂O) (<b>3</b>), and [Yb(H₂O)₈]·(H₃Mel)·8.5(H₂O) (<b>4</b>), have been synthesized in solution at room temperature and characterized by elemental analysis, IR spectrum, and single-crystal X-ray diffraction. The crystal structures of <b>1</b> and <b>2</b> are made up of a (4⁴, 6²) 2-D network extended infinitely parallel to the (1 0 0) plane. The H₃chhc³⁻ anions assume a <i>cis</i>-<i>e,a,e,a,e,a</i>-conformation with the central ring in chair-shaped configuration. In <b>3</b> and <b>4</b>, the H₃Mel³⁻ as counter ions are interconnected by hydrogen bonds to form 2-D organic supramolecular layers. The coordination modes and abilities of H₆chhc and mellitic acid are discussed and compared. The luminescences of <b>1–4</b> have been investigated.</p></div

Surfactant-Mediated One-Pot Method To Prepare Pd–CeO₂ Colloidal Assembled Spheres and Their Enhanced Catalytic Performance for CO Oxidation

A simple, one-pot method to fabricate ordered, monodispersed Pd–CeO₂ colloidal assembled spheres (CASs) was developed using the surfactant-mediated solvothermal approach, which involves a tunable self-assembled process by carefully controlling different chemical reactions. The evolution process and formation mechanism of the CASs were thoroughly investigated by time-controlled and component-controlled experiments. For CO oxidation, this CAS nanocatalyst exhibited much higher catalytic activity and thermal stability than Pd/CeO₂ prepared by an impregnation method, and its complete CO conversion temperature is ∼120 °C. The enhanced catalytic performance for CO oxidation could be attributed to the synergistic effect of highly dispersed PdO species and Pd²⁺ ions incorporated into the CeO₂ lattice. For this CAS catalyst, each sphere can be viewed as a single reactor, and its catalytic performance can be further improved after being supported on alumina, which is obviously higher than results previously reported. Furthermore, this method was used to successfully prepare M–CeO₂ CASs (M = Pt, Cu, Mn, Co), showing further that this is a new and ideal approach for fabricating active and stable ceria-based materials

Effect of One-Pot Rehydration Process on Surface Basicity and Catalytic Activity of Mg_<i>y</i>Al_1‑aREE_<i>a</i>O_<i>x</i> Catalyst for Aldol Condensation of Citral and Acetone

The liquid phase synthesis of pseudoionones (PS) by the cross-aldol condensation of citral and acetone was investigated over MgAl mixed oxides containing rare earth elements (REE = Y, La, Eu), which were obtained from corresponding REE-modified hydrotalcite materials after calcination. The results showed that the unmodified and La­(Eu)-modified MgAl mixed oxide catalysts showed relatively low activity, and Y-modified MgAl mixed oxides presented an unexpected high catalytic activity. PS selectivity of ∼85% and citral conversion of 100% were achieved at 60 °C for 3 h. On the basis of the characterizations of the structural, textural, and basic properties, it was found that Mg₃Al_1‑aY_aO_<i>x</i> catalysts exhibited relatively well-developed small flake morphology with high surface area and pore volume, resulting in exposure of more basic sites on the catalyst surface. The formation of PS over Mg₃Al_1‑aY_aO_<i>x</i> may be accompanied by gradual modification of the catalyst surface to form re-Mg₃Al_1‑aY_aO_<i>x</i> through a rehydration process with produced water, which reconverts the O^2– basic sites to OH^– basic groups. Unlike La and Eu elements, the presence of Y could promote this “one-pot” or <i>in situ</i> rehydration process of MgAl mixed oxides during the aldol reaction. This Y-modified MgAl mixed oxides after a one-pot rehydration process with active Brønsted basic sites is responsible for the high activity in the cross-aldol condensation of citral and acetone

Production of Ethylene Glycol and Its Monoether Derivative from Cellulose

The efficient usage of lignocellulosic biomass is of great significance for large-scale low-cost biomass conversion to biofuels and other useful chemicals. Here, an interesting catalytic process was reported related to converting cellulose into ethylene glycol (EG) and ethylene glycol monoether (EGME) in methanol over a Ru/NbOPO₄ catalyst, with the cleavage of a C–C bond by NbOPO₄ and further hydrogenation by supported Ru particles. The influence of reaction temperature, hydrogen pressure, and reaction time was systematically investigated and showed that a 54.5% total yield of EG and EGME could be obtained at 220 °C in 3 M Pa H₂, which was an exciting result. Meanwhile, the effect of solvent was also studied in detail. It was shown that methanol played an important role in the production of EG and EGME, especially in the cleavage of the C–C bond. Methanol could protect the CO bond in glucose produced from cellulose through acetalization, thus prevent its hydrogenation, and led to the production of EG and EGME. Furthermore, the influence of dopants (W, Sn, Ni, Cu) was further investigated, and it was found that only the Ru–Ni/NbOPO₄ catalyst was more effective through limiting the further hydrogenolysis of products (EG and EGME) to CO and alkanes, and as high as 64% total yield of EG+EGME was achieved. Moreover, the Ru–Ni/NbOPO₄ catalyst showed good reusability, which can be reused at least four times with a little loss in EG and EGME yield

A Highly Effective Catalyst of Sm-MnO_<i>x</i> for the NH₃‑SCR of NO_<i>x</i> at Low Temperature: Promotional Role of Sm and Its Catalytic Performance

Sm-Mn mixed oxide catalysts prepared by the coprecipitation method were developed, and their catalytic activities were tested for the selective catalytic reduction (SCR) of NO with ammonia at low temperature. The results showed that the amount of Sm markedly influenced the activity of the MnO_<i>x</i> catalyst for SCR, that the activity of the Sm-Mn mixed oxide catalyst exhibited a volcano-type tendency with an increase in the Sm content, and that the appropriate mole ratio of Sm to Mn in the catalyst was 0.1. In addition, the presence of Sm in the MnO_<i>x</i> catalyst can obviously enhance both water and sulfur dioxide resistances. The effect of Sm on the physiochemical properties of the Sm-MnO_<i>x</i> catalyst were investigated by XRD, low-temperature N₂ adsorption, XPS, and FE-SEM techniques. The results showed that the presence of Sm in the Sm-MnO_<i>x</i> catalyst can restrain the crystallization of MnO_<i>x</i> and increase its surface area and the relative content of both Mn⁴⁺ and surface oxygen (O_S) on the surface of the Sm-MnO_<i>x</i> catalyst. NH₃-TPD, NO-TPD, and in situ DRIFT techniques were used to investigate the absorption of NH₃ and NO on the Sm-MnO_<i>x</i> catalyst and their surface reactions. The results revealed that the presence of Sm in the Sm_0.1-MnO_<i>x</i> catalyst can increase the absorption amount of NH₃ and NO on the catalyst and does not vary the SCR reaction mechanism over the MnO_<i>x</i> catalyst: that is, the coexistence of Eley–Rideal and Langmuir–Hinshelwood mechanisms (bidentate nitrate is the active intermediate), in which the Eley–Rideal mechanism is predominant

Effect of Ceria Crystal Plane on the Physicochemical and Catalytic Properties of Pd/Ceria for CO and Propane Oxidation

Ceria nanocrystallites with different morphologies and crystal planes were hydrothermally prepared, and the effects of ceria supports on the physicochemical and catalytic properties of Pd/CeO₂ for the CO and propane oxidation were examined. The results showed that the structure and chemical state of Pd on ceria were affected by ceria crystal planes. The Pd species on CeO₂-R (rods) and CeO₂-C (cubes) mainly formed Pd_<i>x</i>Ce_1–<i>x</i>O_2−σ solid solution with −Pd²⁺–O^2––Ce⁴⁺– linkage. In addition, the PdO_<i>x</i> nanoparticles were dominated on the surface of Pd/CeO₂-O (octahedrons). For the CO oxidation, the Pd/CeO₂-R catalyst showed the highest catalytic activity among three catalysts, its reaction rate reached 2.07 × 10^–4 mol g_Pd^–1 s^–1 at 50 °C, in which CeO₂-R mainly exposed the (110) and (100) facets with low oxygen vacancy formation energy, strong reducibility, and high surface oxygen mobility. TOF of Pd/CeO₂-R (3.78 × 10^–2 s^–1) was much higher than that of Pd/CeO₂-C (6.40 × 10^–3 s^–1) and Pd/CeO₂-O (1.24 × 10^–3 s^–1) at 50 °C, and its activation energy (<i>E</i>_a) was 40.4 kJ/mol. For propane oxidation, the highest reaction rate (8.08 × 10^–5 mol g_Pd^–1 s^–1 at 300 °C) was obtained over the Pd/CeO₂-O catalyst, in which CeO₂-O mainly exposed the (111) facet. There are strong surface Ce–O bonds on the ceria (111) facet, which favors the existence of PdO particles and propane activation. The turnover frequency (TOF) of the Pd/CeO₂-O catalyst was highest (3.52 × 10^–2 s^–1) at 300 °C and its <i>E</i>_a value was 49.1 kJ/mol. These results demonstrate the inverse facet sensitivity of ceria for the CO and propane oxidation over Pd/ceria

Incorporating Rich Mesoporosity into a Ceria-Based Catalyst via Mechanochemistry

Ceria-based materials possessing mesoporous structures afford higher activity than the corresponding bulk materials in CO oxidation and other catalytic applications, because of the wide pore channel and high surface area. The development of a direct, template-free, and scalable technology for directing porosity inside ceria-based materials is highly welcome. Herein, a family of mesoporous transition-metal-doped ceria catalysts with specific surface areas up to 122 m² g^–1 is constructed by mechanochemical grinding. No templates, additives, or solvents are needed in this process, while the mechanochemistry-mediated restructuring and the decomposing of the organic group led to plentiful mesopores. Interestingly, the copper species are evenly dispersed in the ceria matrix at the atomic scale, as observed in high resolution scanning transmission electron microscopy in high angle annular dark field. The copper-doped ceria materials show good activity in the CO oxidation

Low-Temperature Methane Combustion over Pd/H-ZSM-5: Active Pd Sites with Specific Electronic Properties Modulated by Acidic Sites of H‑ZSM‑5

Pd/H-ZSM-5 catalysts could completely catalyze CH₄ to CO₂ at as low as 320 °C, while there is no detectable catalytic activity for pure H-ZSM-5 at 320 °C and only a conversion of 40% could be obtained at 500 °C over pure H-ZSM-5. Both the theoretical and experimental results prove that surface acidic sites could facilitate the formation of active metal species as the anchoring sites, which could further modify the electronic and coordination structure of metal species. PdO_<i>x</i> interacting with the surface Brönsted acid sites of H-ZSM-5 could exhibit Lewis acidity and lower oxidation states, as proven by the XPS, XPS valence band, CO-DRIFTS, pyridine FT-IR, and NH₃-TPD data. Density functional theory calculations suggest PdO_<i>x</i> groups to be the active sites for methane combustion, in the form of [AlO₂]­Pd­(OH)-ZSM-5. The stronger Lewis acidity of coordinatively unsaturated Pd and the stronger basicity of oxygen from anchored PdO_<i>x</i> species are two key characteristics of the active sites ([AlO₂]­Pd­(OH)-ZSM-5) for methane combustion. As a result, the PdO_<i>x</i> species anchored by Brønsted acid sites of H-ZSM-5 exhibit high performance for catalytic combustion of CH₄ over Pd/H-ZSM-5 catalysts

Synthesis of Nonspherical Mesoporous Silica Ellipsoids with Tunable Aspect Ratios for Magnetic Assisted Assembly and Gene Delivery

Despite the extensive application of ellipsoidal micro-/nanoparticles, the synthesis of shape anisotropic ellipsoids is rare because of the minimization of surface free energy that favors simple spherical shape rather than complex nonspherical shape. We present the synthesis of silica ellipsoids with hexagonal mesostructure via the organic–inorganic cooperative assembly in the presence of cosolvents (KCl and ethanol). The aspect ratio of ellipsoids can be tuned systematically by controlling the concentration of ethanol. Transmission electron microscopy (TEM) shows that the ellipsoid possesses one-dimensional (1-D) pore channels parallel to the major axis, and the electron tomography (ET) technique shows that the ellipsoid has indeed hexagonal prism morphology in the middle and ellipsoidal morphology at two tips. A mechanism for the formation of mesoporous silica ellipsoids has been proposed. Importantly, magnetite/silica composite ellipsoids were prepared through a nanocasting route and can be used as building blocks to organize into ordered arrays in response to an external magnetic field. In addition, after functionalized with amino-groups, the amino-modified anisotropic magnetite/silica ellipsoids can be further used as carriers for delivering oligo-DNA-Cy3 into tumor cells, showing potential in directed self-assembly and drug/gene delivery

Synthesis of Nonspherical Mesoporous Silica Ellipsoids with Tunable Aspect Ratios for Magnetic Assisted Assembly and Gene Delivery

Despite the extensive application of ellipsoidal micro-/nanoparticles, the synthesis of shape anisotropic ellipsoids is rare because of the minimization of surface free energy that favors simple spherical shape rather than complex nonspherical shape. We present the synthesis of silica ellipsoids with hexagonal mesostructure via the organic–inorganic cooperative assembly in the presence of cosolvents (KCl and ethanol). The aspect ratio of ellipsoids can be tuned systematically by controlling the concentration of ethanol. Transmission electron microscopy (TEM) shows that the ellipsoid possesses one-dimensional (1-D) pore channels parallel to the major axis, and the electron tomography (ET) technique shows that the ellipsoid has indeed hexagonal prism morphology in the middle and ellipsoidal morphology at two tips. A mechanism for the formation of mesoporous silica ellipsoids has been proposed. Importantly, magnetite/silica composite ellipsoids were prepared through a nanocasting route and can be used as building blocks to organize into ordered arrays in response to an external magnetic field. In addition, after functionalized with amino-groups, the amino-modified anisotropic magnetite/silica ellipsoids can be further used as carriers for delivering oligo-DNA-Cy3 into tumor cells, showing potential in directed self-assembly and drug/gene delivery