Unraveling the Structure-Activity-Stability Relationship over Gallium-Promoted HZSM-5 Nanocrystalline Aggregates for Propane Aromatization.

The aromatization of light alkane is an important process for increasing the aromatic production and utilization efficiency of light alkane resources simultaneously. Herein, Ga-modified HZSM-5 catalysts were prepared and investigated by a series of characterization techniques such as X-ray diffraction, nuclear magnetic resonance spectroscopy, transmission electron microscopy, N2 adsorption-desorption, and NH3 temperature-programmed desorption to study their physicochemical properties. The catalytic performance in propane aromatization was also tested. Importantly, the structure-activity relationship, reaction pathway, and coke formation mechanism in propane aromatization were systematically explored. It was found that different Ga introduction methods would affect the amounts of Brønsted and Lewis acid sites, and Ga-HZSM-5 prepared by the hydrothermal method exhibited higher amounts of Brønsted and Lewis acid sites but a lower B/L ratio. As a result, Ga-HZSM-5 showed higher propane conversion and benzene, toluene, and xylene yield compared with that of Ga2O3/HZSM-5. The propane aromatization reaction pathway indicated that propane dehydrogenation to propene was a crucial step for aromatic formation. The increase of the Lewis acid density in Ga-HZSM-5 can effectively improve the dehydrogenation rate and promote the aromatization reaction. Furthermore, the formation of coke species was studied by thermogravimetry-mass spectrometry and Raman approaches, the results of which indicated that the graphitization degree of coke formed over spent Ga-HZSM-5 is lower, resulting in enhanced anticoking stability.

Synergetic Regulation of the Microstructure and Acidity of HZSM-5/MCM-41 for Efficient Catalytic Cracking of n-Decane.

Alkane catalytic cracking is regarded as one of the most significant processes for light olefin production; however, it suffers from serve catalyst deactivation due to coke formation. Herein, HZSM-5/MCM-41 composites with different Si/Al2 ratios were first prepared by the hydrothermal method. The physicochemical properties of the prepared catalysts were analyzed by a series of bulk and surface characterization methods, and the catalytic performance was tested in n-decane catalytic cracking. It was found that HZSM-5/MCM-41 showed a higher selectivity to light olefins and a lower deactivation rate compared with the parent HZSM-5 due to an enhanced diffusion rate and decreased acid density. Moreover, the structure-reactivity relationship revealed that conversion, light olefin selectivity, and the deactivation rate strongly depended on the total acid density. Furthermore, HZSM-5/MCM-41 was further extruded with γ-Al2O3 to obtain the catalyst pellet, which showed an even higher selectivity to light olefins (∼48%) resulting from the synergy effect of the fast diffusion rate and passivation of external acid density.

Magnetically-separable acid-resistant CoFe2O4@Polymer@MIL-100 core-shell catalysts for the acetalization of benzaldehyde and methanol.

Novel reusable acid-resistant magnetic polymer nanospheres-immobilized MIL-100 (CoFe2O4@Polymer@MIL-100) catalyst was prepared by a layer-by-layer method to achieve a controllable structure. The obtained core-shell catalyst consisted of modified magnetic nanoparticles as the core, a carboxylic-functionalized polymer as the protective layer, and an MIL-100 shell as the active catalytic layer by chemical bonds on the polymer. The catalysts showed good stability, good magnetic saturation, and acid corrosion resistance. The thickness of the MIL-100 shell could be adjusted by controlling the metal salt concentration and the number of layer-by-layer cycles. Nano-sized MIL-100 showed better mass transfer efficiency and catalytic activity. A conversion of 97.7% after 10 min was observed during acetalization when using CoFe2O4@Polymer@MIL-100 as the catalyst. CoFe2O4@Polymer@MIL-100 could be reused at least five times. The use of a polymer layer on CoFe2O4@Polymer@MIL-100 prevented acidic ligands from corroding the magnetic core. Chemical bonds between MIL-100 and functional magnetic polymer cores improved the catalyst's stability. CoFe2O4@Polymer@MIL-100 exhibited high activity, excellent stability, and easy magnetic separation.

Novel Side-Chain Type Sulfonated Poly(phenylquinoxaline) Proton Exchange Membranes for Direct Methanol Fuel Cells.

Side-chain type sulfonated poly(phenylquinoxaline) (SPPQ)-based proton exchange membranes (PEMs) with different ionic exchange capacity (IEC) were successfully synthesized by copolymerization from 4,4'-bis (2-diphenyletherethylenedione) diphenyl ether, 4,4'-bis (2-phenylethylenedione) diphenyl ether and 3,3',4,4'-tetraaminobiphenyl, and post-sulfonation process. The sulfonic acid groups were precisely grafted onto the p-position of phenoxy groups in the side chain of PPQ after the convenient condition of the post-sulfonation process, which was confirmed by 1H NMR spectra and FTIR. The sulfonic acid groups of side-chain type SPPQ degraded at around 325 °C, and their maximum stress was higher than 47 MPa, indicating great thermal and mechanical stability. The water uptake increased with the increasing IEC and temperature. The size change in their plane direction was shown to be lower than 6%, indicating the stability of membrane electrode assembly. The SPPQ PEMs displayed higher proton conductivity than that of main chain. In the single cell test, the maximum power density of side-chain type SPPQ-5 was 63.8 mW cm-2 at 20 wt% methanol solution and O2 at 60 °C, which is largely higher than 18.4 mW cm-2 of NR212 under the same conditions. The SPPQ PEMs showed high performance (62.8 mW cm-2) even when the methanol concentration was as high as 30 wt%.

Metal - organic frameworks derived Ni5P4/NC@CoFeP/NC composites for highly efficient oxygen evolution reaction.

As an efficient non-precious metal catalyst for the oxygen evolution reaction (OER), phosphides suffer from poor electrical conductivity, so it is still a challenge to reasonably design their structures to further improve their conductivity and OER performances. Here, we present a novel Ni5P4/N-doped carbon@CoFeP/N-doped carbon composite (Ni5P4/NC@CoFeP/NC) as electrocatalysts for OER. This elaborate structure consists of Ni5P4/NC derived from Ni-MOF and CoFeP/NC derived from CoFe-Prussian blue analog MOF (Co-Fe PBA). The cube-like CoFeP/NC are scattered and uniformly coated on the sheet of Ni5P4/NC flowers. Among them, NC can enhance the conductivity of phosphides, while CoFeP/NC can increase the electrochemical active area, which benefit the properties of Ni5P4/NC@CoFeP/NC. Notably, the Ni5P4/NC@CoFeP/NC catalyst possesses outstanding OER performances with a low overpotential of 260 and 303 mV at a current density of 10 and 100 mA·cm-2, an ultra-low Tafel slope of 31.1 mV·dec-1 and excellent stability in 1 M KOH. XPS analysis shows that proper chemical composition promotes the oxidation of transition metal species and the chemisorption of OH-, thus accelerating the OER kinetics. Therefore, this work provides a hopeful method for designing and preparing transition metal phosphide/carbon composite as OER electrocatalysts.

Cu/NC@Co/NC composites derived from core-shell Cu-MOF@Co-MOF and their electromagnetic wave absorption properties.

Metal-organic-frameworks (MOFs) derived carbon or nitrogen-doped carbon (NC) materials are usually used as electromagnetic wave (EMW) absorbers. However, the effective control of the composition and structure of composites is still a major challenge for the development of high-performance EMW absorbing materials. In this work, core-shell structure and bimetallic composition Cu/nitrogen doped carbon @Co/ nitrogen doped carbon (Cu/NC@Co/NC) composites were designed and synthesized through the thermal decomposition of Cu-MOF@Co-MOF precursor. Cu/NC@Co/NC composites with different compositions were obtained by changing the ratio of Co-MOF and Cu-MOF. The composite (Cu/NC@Co/NC-3.75) prepared using 3.75 mmol of Co(NO3)2·6H2O exhibits outstanding EMW absorption properties due to the optimized impedance matching and strong attenuation ability, which is caused by enhanced interfacial and dipolar polarization as well as multiple reflection and scattering. With the filler loading in paraffin of 35 wt%, the minimum reflection loss (RLmin) is up to -54.13 dB at 9.84 GHz with a thin thickness of 3 mm, and the effective absorption bandwidth (EAB, RL≤ - 10 dB) reaches 5.19 GHz (10.18-15.37 GHz) with the corresponding thickness of 2.5 mm. Compared with the Cu/NC and Co/NC, the Cu/NC@Co/NC-3.75 composite exhibits much better EMW absorbing performances caused by the bimetallic composition and the unique core-shell structure. This work provides a rational design for MOF-derived lightweight and broadband EMW absorbing materials.

Pomegranate-like Core-Shell Ni-NSs@MSNSs as a High Activity, Good Stability, Rapid Magnetic Separation, and Multiple Recyclability Nanocatalyst for DCPD Hydrogenation.

A novel pomegranate-like Ni-NSs@MSNSs nanocatalyst was successfully synthesized via a modified Stöber method, and its application in the hydrogenation of dicyclopentadiene (DCPD) was firstly reported. The Ni-NSs@MSNSs possessed a high specific area (658 m2/g) and mesoporous structure (1.7-3.3 nm). The reaction of hydrogenation of DCPD to endo-tetrahydrodicyclopentadiene (endo-THDCPD) was used to evaluate the catalytic performance of the prepared materials. The distinctive pomegranate-like Ni-NSs@MSNSs core-shell nanocomposite exhibited superior catalytic activity (TOF = 106.0 h-1 and STY = 112.7 g·L-1·h-1) and selectivity (98.9%) than conventional Ni-based catalysts (experimental conditions: Ni/DCPD/cyclohexane = 1/100/1000 (w/w), 150 °C, and 2.5 MPa). Moreover, the Ni-NSs@MSNSs nanocatalyst could be rapidly and conveniently recycled by magnetic separation without appreciable loss. The Ni-NSs@MSNSs also exhibited excellent thermal stability (≥750 °C) and good recycling performance (without an activity and selectivity decrease in four runs). The superior application performance of the Ni-NSs@MSNSs nanocatalyst was mainly owing to its unique pomegranate-like structure and core-shell synergistic confinement effect.

Synthesis of Surface-Active Heteropolyacid-Based Ionic Liquids and Their Catalytic Performance for Desulfurization of Fuel Oils.

Surface-active heteropolyacid-based ionic liquids with varying alkyl carbon chains were synthesized, which were subsequently analyzed. The desulfurization of fuels was investigated utilizing various surface-active heteropolyacid-based ionic liquids, and acetonitrile was used as the extractant for the coupling of ODS and EDS. The influences of the alkyl group, surface activity, and hydrophobicity of ionic liquids on sulfur removal were studied. The results suggested that the ionic liquids were stable. Among these ionic liquids, [C4ImBS]3[PW12O40] exhibited the best catalytic performance. Using [C4ImBS]3[PW12O40] as the catalyst, the influences of the catalyst amount, aqueous hydrogen peroxide amount, and reaction temperature on the sulfur removal were explored. Under the optimum conditions, the sulfur removal could achieve 100% efficiency. The recycle experiments also proved that the ionic liquid could be reused.

Rational Design of Hierarchical Structural CoSe@NPC/CoSe@CNT Nanocomposites Derived from Metal-Organic Frameworks as a Robust Pt-free Electrocatalyst for Dye-Sensitized Solar Cells.

Transition-metal compounds/carbon hybrids with high electrocatalytic capability possess attractive potential as a counter electrode (CE) for dye-sensitized solar cells (DSSCs). However, the simple structure and agglomeration always result in poor performance. Herein, cobalt selenides confined in hollow N-doped porous carbon interconnected by carbon nanotubes (CNTs) with cobalt selenides encapsulated inside (denoted as CoSe@NPC/CoSe@CNTs) are formed through in situ pyrolysis and selenization process. In this strategy, ZIF-67 is used as the precursor, structure inducer, and carbon source for the orientated growth of CNTs. Such a rational architecture provides a stable interconnected conductive network and a hierarchically porous structure, with more available active sites and a shortened pathway for charge transport, synergistically enhancing the electrocatalytic activity. Specifically, the DSSCs based on CoSe@NPC/CoSe@CNTs demonstrate a high efficiency of 7.36%, even superior to that of Pt (7.16%). Furthermore, the CoSe@NPC/CoSe@CNT CE also demonstrates a good long-term stability in the iodine-based electrolyte.

Structural Regulation of Magnetic Polymer Microsphere@Ionic Liquids with an Intermediate Protective Layer and Application as Core-Shell-Shell Catalysts with High Stability and Activity.

A novel ionic liquid immobilized on a magnetic polymer microsphere catalyst is reported in this paper. The obtained core-shell-shell catalyst consisted of magnetic nanoparticles (MNPs) as the core, catalytic inert St-co-DVB as the intermediate protective layer, and cross-linked polyaryl imidazole ionic liquids as the active catalytic layer located at the outermost [Im[OH]/MNPs@P(St-DVB)@P(VBC-DVB)]. This catalyst exhibited a high ion-exchange rate (64.65%), high saturation magnetic strength, and excellent acid and alkali corrosion resistance. In the catalyzed Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, the conversion of benzaldehyde maintained at 92.1% during six times reuse. Optimizing the materials of the protective layer and regulating the thickness of the inert protective layer decreased the corrosion ratio of MNPs in acidic media from 44.82 to 0.44%. Adjusting the thickness of the catalytic layer realized excellent catalytic activity (97%) and high magnetic response performance. In summary, introducing an inert protective layer to the structure of ionic liquids immobilized on the magnetic polymer microsphere catalyst, regulating its thickness, and optimizing its structure achieved a catalyst with high activity, excellent stability, and easy magnetic separation.

Rational Construction of Hierarchically Porous Fe-Co/N-Doped Carbon/rGO Composites for Broadband Microwave Absorption.

Developing lightweight and broadband microwave absorbers for dealing with serious electromagnetic radiation pollution is a great challenge. Here, a novel Fe-Co/N-doped carbon/reduced graphene oxide (Fe-Co/NC/rGO) composite with hierarchically porous structure was designed and synthetized by in situ growth of Fe-doped Co-based metal organic frameworks (Co-MOF) on the sheets of porous cocoon-like rGO followed by calcination. The Fe-Co/NC composites are homogeneously distributed on the sheets of porous rGO. The Fe-Co/NC/rGO composite with multiple components (Fe/Co/NC/rGO) causes magnetic loss, dielectric loss, resistance loss, interfacial polarization, and good impedance matching. The hierarchically porous structure of the Fe-Co/NC/rGO enhances the multiple reflections and scattering of microwaves. Compared with the Co/NC and Fe-Co/NC, the hierarchically porous Fe-Co/NC/rGO composite exhibits much better microwave absorption performances due to the rational composition and porous structural design. Its minimum reflection loss (RLmin) reaches - 43.26 dB at 11.28 GHz with a thickness of 2.5 mm, and the effective absorption frequency (RL ≤ - 10 dB) is up to 9.12 GHz (8.88-18 GHz) with the same thickness of 2.5 mm. Moreover, the widest effective bandwidth of 9.29 GHz occurs at a thickness of 2.63 mm. This work provides a lightweight and broadband microwave absorbing material while offering a new idea to design excellent microwave absorbers with multicomponent and hierarchically porous structures.

Green Synthesis of Porous Cocoon-like rGO for Enhanced Microwave-Absorbing Performances.

A novel porous cocoon-like reduced graphene oxide (rGO) with high porosity and low density was fabricated by a simple and green reduction reaction using ascorbic acid as the reductant in combination with a freeze-drying process without annealing. The bulk density of porous cocoon-like rGO is only 28.49 mg/cm3, and the porosity reaches 94.57%. The reaction times have an important influence on the formation of porous cocoon-like rGO and the reduction degree of rGO. The porous cocoon-like rGO exhibits an excellent microwave-absorbing property with a low mass filling ratio of 7.0 wt %; its minimum reflection loss (RL) is -29.05 dB at 15.96 GHz with a sample thickness of 2.0 mm and the effective absorption bandwidth (RL < -10 dB) is 5.27 GHz. The microwave-absorbing property of porous cocoon-like rGO is much better than that of GO and other porous rGO. The in-depth analyses of the reduction degree, porosity, and microwave-absorbing performance illustrate that the microwave-absorbing performance of rGO is significantly related to the reduction degree and porosity. In addition, the synthetic route for porous cocoon-like rGO is simple, has low energy consumption, and is environmentally friendly. Our work demonstrates that the porous cocoon-like rGO is a promising lightweight microwave absorber with high performance.

A convenient four-component one-pot strategy toward the synthesis of pyrazolo[3,4-d]pyrimidines.

An efficient one-pot synthesis of pyrazolo[3,4-d]pyrimidine derivatives by the four-component condensation of hydrazines, methylenemalononitriles, aldehydes and alcohols has been developed via two different reaction pathways. The structures of target products were characterized by IR spectroscopy, NMR ((1)H and (13)C) spectroscopy and HRMS (ESI) spectrometry. The crystal structure of 4-ethoxy-6-(2-nitrophenyl)-1-phenyl-1H-pyrazolo[3,4-d]pyrimidine was determined by single crystal X-ray diffraction.

N-(2-Methyl-3-oxo-1,3-diphenyl-prop-yl)acetamide.

In the title compound, C18H19NO2, the dihedral angle between the benzene rings is 42.0 (1)°. In the crystal, mol-ecules are linked by N-H⋯O and C-H⋯π inter-actions.

Pseudoaglycone of spinosyn a.

THE TITLE COMPOUND [SYSTEMATIC NAME: 9-ethyl-13-hy-droxy-14-methyl-2-(3,4,5-trimeth-oxy-6-methyl-tetra-hydro-2H-pyran-2-yl-oxy)-3,3a,5b,6,9,10,11,12,13,14,16a,16b-dodeca-hydro-1H-as-indaceno[3,2-d][1]oxacyclo-dodecine-7,15(2H,5aH)-dione], C(33)H(50)O(9), was obtained by hydrolysis of Spinosyn A. The fused cyclo-pentene ring adopts a twisted conformation, while the fused cyclo-hexene and cyclo-pentane rings are in envelope conformations with the same C atom at the flaps. In the crystal, mol-ecules are linked by O-H⋯O and C-H⋯O hydrogen bonds into a layer parallel to the ab plane.

7'-Amino-1'H-spiro-[cyclo-heptane-1,2'-pyrimido[4,5-d]pyrimidin]-4'(3'H)-one.

The title compound, C(12)H(17)N(5)O, was obtained by cyclo-condensation of 2,4-diamino-pyrimidine-5-carbonitrile with cyclo-hepta-none. The tetra-hydro-pyrimidine ring has a dis-torted boat conformation and the cyclo-heptane ring adopts a chair conformation. In the crystal, molecules are linked via N-H⋯O and N-H⋯N hydrogen bonds generating a three-dimensional network.

6'-Bromo-1'H-spiro-[cyclo-hexane-1,2'-pyrido[2,3-d]pyrimidin]-4'(3'H)-one.

The title compound, C(12)H(14)BrN(3)O, is built up from two fused six-membered rings and one six-membered ring linked through a spiro C atom. The hydro-pyrimidine ring has an envelope conformation and the cyclo-hexane ring is in a chair conformation. In the crystal, mol-ecules are linked by N-H⋯O and N-H⋯N hydrogen bonds, forming a mol-ecular tape along the b axis.

5'-Methyl-sulfanyl-4'-oxo-7'-phenyl-3',4'-dihydro-1'H-spiro-[cyclo-hexane-1,2'-quinazoline]-8'-carbonitrile dimethyl-formamide monosolvate.

In the title compound, C(21)H(21)N(3)OS·C(3)H(7)NO, the carbonitrile mol-ecule is built up of two fused six-membered rings and one six-membered ring linked through a spiro C atom. The 1,3-diaza ring adopts an envelope conformation and the cyclo-hexane ring adopts a chair conformation. The dihedral angle between the aromatic rings is 46.7 (3)°. In the crystal, the components are linked by N-H⋯O hydrogen bonds.

5'-Methyl-4'-oxo-7'-phenyl-3',4'-dihydro-1'H-spiro-[cyclo-hexane-1,2'-quinazoline]-8'-carbonitrile.

The title compound, C(21)H(21)N(3)O, was obtained by cyclo-condensation of 3-amino-5-methyl-[1,1'-biphen-yl]-2,4-di-car-bo-nitrile with cyclo-hexa-none. The six-membered 1,3-diaza ring assumes an envelope conformation [with the flap atom displaced by 0.511 (7) Šfrom the plane through the other ring atoms] and the cyclo-hexane ring displays a chair conformation. The dihedral angle between the aromatic rings is 42.61 (7)°.In the crystal, the mol-ecules form hydrogen-bonded bands along [011].

Spiro-[cyclo-pentane-1,2'(1'H)-pyrido[2,3-d]pyrimidin]-4'(3'H)-one.

The title compound, C(11)H(13)N(2)O, was obtained by cyclo-condensation of 2-amino-pyridine-3-carbonitrile with cyclo-penta-none. The mol-ecule is built up from two fused six-membered rings and one five-membered ring linked through a spiro C atom. Both the pyrimidine and the cyclo-pentane rings adopt envelope conformations. In the crystal structure, mol-ecules are linked by inter-molecular N-H⋯O hydrogen bonds.