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1.
J Org Chem ; 85(5): 3101-3109, 2020 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-31944763

RESUMO

Precise catalytic regulation of carbon radical generation by a highly active oxygen radical to abstract the H atom in a C-H bond is an effective method for the selective activation of C-H synthetic chemistry. Herein, we report a facile catalyst system with commercially available copper(II)/{PMo12} to form a tert-butanol radical intermediate for the selective oxidation of benzylic C-H bonds. The reaction shows a broad range of substrates (benzyl methylene, benzyl alcohols) with good functional group tolerance and chemical selectivity. The corresponding carbonyl compounds were synthesized with good yields under mild conditions. DFT calculations and experimental analysis further demonstrated a reasonable carbon radical mechanism for this type of organic transformation reaction.

2.
J Nanosci Nanotechnol ; 19(9): 5999-6005, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-30961773

RESUMO

The structural and textural properties of the Ce0.9Pr0.1O2-δ (CP) and Ce0.9Pr0.1O2-δ (CT) solid solutions were investigated by X-ray diffraction (XRD), BET surface area, transmission electron microscopy (TEM-HRTEM), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), Raman spectra, and X-ray photoelectron spectroscopy (XPS). The redox recoverability and catalytic activity were analyzed by temperature-programmed reduction (TPR) and oxidation reaction using carbon monoxide as a probe molecule. It was found that the CP solid solution exhibited better structural thermal stability, oxygen storage/release capacity, as well as redox ability than that of CT solid solution, since that the microstructure and oxygen vacancy concentration of CP sample under actual using process could recover to its initial status more easily in oxygen, even at room temperature. Therefore, the CP sample presented better CO oxidation activity compared with that of CT solid solution.

3.
Dalton Trans ; 48(16): 5285-5291, 2019 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-30869728

RESUMO

The Keggin-type mono-transition-metal-substituted [PW11M(H2O)O39]5- (PW11M, M = Ni, Co, Cu) were intercalated into Zn2Cr-based layered double hydroxide (Zn2Cr-LDH) by an exfoliation-reassembly method and the synthesized Zn2Cr-LDH-PW11M composites were thoroughly characterized by Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (PXRD), solid state 31P nuclear magnetic resonance (31P NMR) spectroscopy, thermogravimetric analysis (TGA), inductively coupled plasma atomic emission spectroscopy (ICP-AES), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The three composites can be used as heterogeneous catalysts to promote the oxidative decontamination of the sulfur mustard simulant 2-chloroethyl ethyl sulfide (CEES). Interestingly, a cooperative effect between the PW11M cluster and Zn2Cr-LDH is evidenced by the fact that the composites have a higher catalytic performance than either of the individual constituents alone. The catalytic activity of Zn2Cr-LDH-PW11M is significantly influenced by the substituted transition metals, showing the order: Zn2Cr-LDH-PW11Ni > Zn2Cr-LDH-PW11Co > Zn2Cr-LDH-PW11Cu. Under ambient conditions, the Zn2Cr-LDH-PW11Ni composite can convert 98% of CEES in 3 h using nearly stoichiometric 3% aqueous H2O2 with the selectivity of 94% for the nontoxic product 2-chloroethyl ethyl sulfoxide (CEESO). Moreover, the decontaminating material, Zn2Cr-LDH-PW11Ni, is stable to leaching and can be readily reused for up to ten cycles without obvious loss of its activity.

4.
Chemistry ; 24(72): 19208-19215, 2018 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-30353931

RESUMO

A decontaminating composite, Mg3 Al-LDH-Nb6 , has been successfully prepared by immobilizing Lindqvist [H3 Nb6 O19 ]5- (Nb6 ) into a Mg3 Al-based layered double hydroxide (Mg3 Al-LDH). To our knowledge, this represents the first successful approach to the immobilization of polyoxoniobate. As a versatile catalyst, Mg3 Al-LDH-Nb6 can effectively catalyze the degradation of both vesicant and nerve agent simulants by multiple pathways under mild conditions. Specifically, the sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES), is converted into the corresponding nontoxic 2-chloroethyl ethyl sulfoxide (CEESO) by selective oxidation, whereas the Tabun (G-type nerve agent) simulant, diethyl cyanophosphonate (DECP), and the VX (V-type nerve agent) simulant, O,S-diethyl methylphosphonothioate (OSDEMP), are detoxified through hydrolysis and perhydrolysis, respectively. A possible mechanism is proposed on the basis of control experiments and spectroscopic studies. The Mg3 Al-LDH-Nb6 composite exhibits remarkable robustness and can be readily reused for up to ten cycles with negligible loss of its catalytic activity. More importantly, a protective "self-detoxifying" material has easily been constructed by integrating Mg3 Al-LDH-Nb6 into textiles. In this way, the flexible and permeable properties of textiles have been combined with the catalytic activity of polyoxoniobate to remove 94 % of CEES in 1 h by using nearly stoichiometric dilute H2 O2 (3 %) as oxidant with 96 % selectivity.

5.
Chem Commun (Camb) ; 54(88): 12471-12474, 2018 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-30338321

RESUMO

The method described herein is a general, efficient and green approach to synthesize α-ketoamides from arylacetic acids and amines. Employing a simple copper(i)/{Nb6O19} catalyst system, the reaction offers a facile process to give functionalized α-ketoamides from readily available arylacetic acids under aerobic conditions. The merit of this new strategy is that it expands the syntheses of α-ketoamides from stable, inexpensive and widely available acylation reagents such as arylacetic acids in one step.

6.
Nanoscale ; 10(43): 20313-20320, 2018 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-30375608

RESUMO

Engineering compositions, structures, and defects can endow nanomaterials with optimized catalytic properties. Here, we report that cobalt oxide (CoOx) ultrathin nanosheets (UTNS, ∼1.6 nm thick) with a large number of oxygen defects and mixed cobalt valences can be obtained through a facile one-step hydrothermal protocol. The large number of oxygen defects make the ultrathin CoOx nanosheet a superior OER catalyst with low overpotentials of 315 and 365 mV at current densities of 50 and 200 mA cm-2, respectively. The stable framework-like architectures of the UTNS further ensure their high OER activity and durability. Our method represents a facile one-step preparation of CoOx nanostructures with tunable compositions, morphologies, and defects, and thus promotes OER properties. This strategy may find its wider applicability in designing active, robust, and easy-to-obtain catalysts for OER and other electrocatalytic systems.

7.
J Hazard Mater ; 344: 994-999, 2018 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-30216973

RESUMO

Amphiphilic polyoxoniobates (PONbs), [CnH2n+1N(CH3)3]7HNb6O19 (for 1, n=14; for 2, n=16; and for 3, n=18), were successfully prepared by the electrostatic interaction of hexaniobate anions with quaternary ammoniums containing long alkyl chain, and thoroughly characterized by using various techniques including Fourier transform infrared (FT-IR), 1H nuclear magnetic resonance (1H NMR), 13C nuclear magnetic resonance (13C NMR), thermogravimetric analysis (TGA), and elemental analysis. All three PONbs were used in the emulsion systems to catalytically decontaminate chemical warfare agent simulants and the influences of quaternary ammonium cations, polyanions, and amount of catalyst on the catalytic efficiency have been evaluated. Under optimal conditions, catalyst 3 in emulsion can completely convert both a the nerve agent simulant, diethyl cyanophosphonate (DECP), in 2h by hydrolysis and a sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES), in 20min by oxidation using nearly stoichiometric 3% aqueous H2O2. Moreover, the amphiphilic catalyst 3 can be simply separated and readily reused for five recycles without obvious losing its activity. To the best of our knowledge, this study represents the first example where the emulsions of PONbs are used in the catalysis.

8.
Inorg Chem ; 57(15): 8831-8840, 2018 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-30015477

RESUMO

The generation of five types of Ln(III)-containing tungstotellurates(VI), dimeric (DMAH)12Na2[H10(WO2){Ln(H2O)5(TeW18O65)}2]· nH2O (abbreviated as {Ln2Te2W37}; Ln = Eu, Gd, or Tb; DMAH = dimethylammonium), tetrameric (DMAH)21Na7[H16{Ln(H2O)5(TeW18O64)}4]· nH2O (abbreviated as {Ln4Te4W72}, Ln = Eu or Gd), 2:2 dimeric (DMAH)12[H6{Tb(H2O)3(TeW17O61)}2]·25H2O (abbreviated as {Tb2Te2W34}), 1:1 monosubstituted (DMAH)7Na2[H2Tb(H2O)4(TeW17O61)]·21H2O (abbreviated as {TbTeW17}), and three-dimensional polymer (DMAH)2[HTb(H2O)4{TeW6O24}]·14H2O (abbreviated as {TbTeW6} n), provides insight into the rich condensation chemistry of lacunary and other Dawson-type polyoxometalates. The pH and the type of Ln3+ source both dictate which of these new complexes form. To our knowledge, {Ln4Te4W72} is the highest-nuclearity tungstotellurate to date, and {Tb2Te2W34} and {TbTeW17} contain the first lacunary {TeW17O61}. Electrospray ionization mass spectra analyses indicate that the Dawson-like building blocks, {TeW18O65} and {TeW17O61}, found in solid structures are also present in solution. The intense photoluminescence (characteristic green emission) of {TbTeW6} n, 100× greater than those of {Tb2Te2W37}, {Tb2Te2W34}, and {TbTeW17}, is explained by analysis of all 4 X-ray structures and multiple structure-intensity correlations.

9.
J Org Chem ; 83(15): 8233-8240, 2018 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-29787264

RESUMO

A general and effective method for the synthesis of alkylamine via intramolecular decarboxylation of alkanoyloxycarbamates is described. The alkanoyloxycarbamates are readily prepared with alkyl carboxylic acids and hydroxylamine. The reaction shows a broad range of substrates (primary and secondary alkyl) with functional tolerance, and the corresponding products were obtained in good yields under mild conditions.

10.
Org Biomol Chem ; 16(14): 2421-2426, 2018 04 04.
Artigo em Inglês | MEDLINE | ID: mdl-29546910

RESUMO

An efficient Pd-catalyzed decarboxylation/cyclization of aroyloxycarbamates to realize substituted indoles has been disclosed. Terminal alkynes as the coupling partners lead to site specific 2-substituted indoles through two pathways, while internal alkynes with aroyloxycarbamates can be transformed to 2,3-disubstituted indoles directly. This protocol is further demonstrated by the efficient synthesis of indoles as well as the success of employing inexpensive aryl acids as starting materials to construct C-N bonds by releasing CO2.

11.
Chemistry ; 24(10): 2466-2473, 2018 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-29205556

RESUMO

The SrII -centered 12-palladate(II) open-cube {SrPd12 (OAc)3 } has been systematically evolved by substitution of the three acetate ligands by a library of saturated carboxylic acids with increasing chain lengths leading to four novel polyoxopalladates(II) with the formula [SrPd12 O6 (OH)3 (PhAsO3 )6 (L)3 ]4- (SrPd12 L3 , L=Cn H2n+1 COO, n=2 to 5). These first examples of surfactant-type polyoxopalladates with a hydrophilic metal-oxo unit and three hydrophobic alkyl chains were characterized in the solid state (single-crystal XRD, FTIR, TGA), in solution (1 H, 13 C NMR spectroscopy), and in the gas phase (ESI-MS). The two polyanions SrPd12 L3 with chain lengths of 5 and 6 are the first examples of polyoxopalladates that are soluble and stable in organic media. The Na salts of the amphiphilic polyoxopalladates SrPd12 L3 were shown to self-assemble into "blackberry"-type spherical supramolecular structures in dilute solutions, of which an unusual "volcano"-shaped trend of assembly size versus solvent polarity is chiefly influenced by directional hydrogen bonding interactions.

12.
Dalton Trans ; 47(3): 726-733, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-29230458

RESUMO

By the combination of Pd-complexes and [V10O28]6-, three Pd-decavanadate compounds [Pd(NH3)4]3[V10O28]·8H2O (1), [Pd(deta)(H2O)]2(NH4)2[V10O28]·2H2O (2) (deta = diethylenetriamine) and [Pd(dpa)2](Hdpa)2(Et3NH)2[V10O28]·2H2O (3) (dpa = 2,2'-dipyridylamine) have been successfully synthesized and thoroughly characterized using single X-ray diffraction (SXRD), powder X-ray diffraction (PXRD), infrared spectroscopy (FT-IR) and elemental analyses (EA). Interestingly, in the three compounds, the molar ratios of Pd to decavanadate vary from 3 : 1 to 1 : 1 by changing N-ligands. The three Pd-decavanadates as heterogeneous catalysts are active in the aerobic oxidation of benzylic hydrocarbons under solvent-free conditions without adding any additives and co-catalysts. Moreover, compound 1 can be reused three times without losing its activity.

13.
Inorg Chem ; 56(23): 14506-14512, 2017 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-29144129

RESUMO

One-pot mechanochemical synthesis was demonstrated to be an efficient strategy to synthesize host-guest POM⊂rho-ZIF complexes (POM = polyoxometalate; rho-ZIF = zeolitic imidazolate framework with rho topology) with high crystallinity. In this work, the metastable rho-ZIF with large interior cavities and windows was used as host matrix for encapsulating and immobilizing bulky guest molecules with high loading efficiency and chemical stability. As novel catalysts, POM⊂rho-ZIF complexes were found effective for the selective oxidation of a series of sulfides to sulfoxides. Moreover, the heterogeneity of these composite catalysts was confirmed by leaching tests, and they can be recycled at least four times without significant loss of activity.

14.
Nanoscale ; 9(32): 11596-11604, 2017 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-28770917

RESUMO

The oxygen evolution reaction (OER) is a vital half-reaction in water splitting and metal-air batteries. Developing earth-abundant, highly efficient and durable OER catalysts has faced huge challenges until now, because OER is a strict kinetic sluggish process. Herein, we report the construction of hierarchically porous graphitized carbon (HPGC) supported NiFe layered double hydroxides (LDHs) with a core-shell structure (denoted as HPGC@NiFe) by a facile strategy. The HPGC was first obtained by pyrolysing phenolic resin nanospheres with FeCl3 and ZnCl2 as the catalyst and the activator, respectively. Then the NiFe LDH arrays were directly grown on the HPGC by a one-step hydrothermal method. The as-synthesized HPGC@NiFe reveals excellent OER properties with a low onset potential, a lower overpotential of 265 mV (corresponding to the current density at 10 mA cm-2) and a small Tafel slope (56 mV per decade). And its catalytic activity is even superior to that of the start-of-the-art noble-metal catalyst IrO2/C. Notably, the HPGC@NiFe electrode shows admirable stability measured by performing 2000 cycle CVs and long-term electrolysis for 50 h. The prominent performance can be attributed to the synergistic effect between the NiFe-LDHs and the hierarchically porous graphitized carbon, in which the former can increase the exposure of the active sites, while the latter can increase the charge transfer efficiency. Our research implies the possibility for the development of low-cost layered double hydroxides as a promising candidate in electrochemical energy storage and conversion equipment.

15.
Inorg Chem ; 56(18): 10844-10847, 2017 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-28845977

RESUMO

An ionic crystal assembled by PNb12O40(VO)6 and tris(1,2-diaminopropane)cobalt complexes was hydrothermally isolated and structurally characterized by routine methods. The compound exhibits three-dimensional channels with a pore size of 3.68 Å × 2.30 Å and composed of hydrophilic oxygen atoms of polyanions and hydrophobic -CH3 groups of 1,2-diaminopropane ligands. With increasing vapor pressure, the compound shows preferable adsorption toward water over alcohols, and a gate-opening behavior was deduced from the water adsorption isotherm.

16.
J Org Chem ; 82(15): 8251-8257, 2017 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-28664735

RESUMO

A new sequential approach for 2-vinylanilines utilizing aryl carboxylic acids as stable, inexpensive and widely available arylating reagents is described. Employing a Pd-POVs catalyst system, this protocol is not only overcoming the restriction barrier of decarboxylative coupling to ortho-substituted substrates, but also provides site-special to create new C(sp2)-N and C(sp2)-C(sp2) bonds. Mechanistic experiments suggest the cleavage of C(sp2)-COOH gives priority to C(sp2)-X bond in this reaction.

17.
Dalton Trans ; 46(25): 8245-8251, 2017 Jun 27.
Artigo em Inglês | MEDLINE | ID: mdl-28612860

RESUMO

Two ionic organic-inorganic hybrid compounds, [CuII(C2N2H8)2]4[CuII(C2N2H8)2(H2O)2]2[PNb12O40VVVIVO2]·(OH)2·11H2O (1) and [CoIII(C2N2H8)3]2[CoIII(C2N2H8)2(H2O)2]0.5[H2.5PNb12O40 VVVIVO2]·20H2O (2), based on P-centered dicapped polyoxoniobates and organometallic cations were isolated and structurally characterized by routine techniques. The trivalent cobalt complex-containing compound exhibits a looser arrangement compared with its divalent copper complex-containing counterpart, with a space volume of 34.9% for the former and 17.0% for the latter. The two compounds were proved to be effective in facilitating the oxidation of benzyl-alkanes to ketone products in a heterogeneous manner, evidencing the feasiblity of the strategy of self-immobilization of catalytically active, readily soluble PNb12O40(VO)2 species in crystalline solids.

18.
Inorg Chem ; 56(10): 5748-5756, 2017 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-28430438

RESUMO

Six alkoxohexavanadate-based Cu- or Co-POVs [Cu(dpa)(acac)(H2O)]2[V6O13(OMe)6] (1), [Cu(phen)(acac)(MeOH)]2[V6O13(OMe)6] (2), [Co(dpa)(acac)2]2[V6O13(OMe)6]·2MeOH (3), [Co(phen)(acac)2]2[V6O13(OMe)6] (4), [Cu(dpa)(acac)]2[VIV2VV4O12(OMe)7] (5), and [Cu(dpa)(acac)(MeOH)]2[VIV2VV4O11(OMe)8] (6) (POV = polyoxovanadate; dpa = 2,2'-dipyridine amine; phen = 1,10-phenanthroline; acac = acetylacetone anion) have been synthesized by controlling the reaction conditions and characterized by single-crystal X-ray diffraction and powder X-ray diffraction analyses, FT-IR spectroscopy, element analyses, and X-ray photoelectron spectroscopy. In compounds 1-4 and 6, Cu or Co complexes and alkoxohexavanadate anions are assembled through electrostatic interactions. Differently, in compound 5, seven-methoxo-substituted Lindqvist-type [V6O12(OMe)7]2- are bridged to Cu complex via terminal O atoms by coordination bonds. All compounds 1-6 exhibit excellent heterogeneous catalytic performance in oxidative desulfurization and CEES ((2-chloroethyl) ethyl sulfide, a sulfur mustard simulant) abatement with H2O2 as oxidant. Among them, the catalytic activity of 6 [conv. of DBT (dibenzothiophene) up to 100% in 6 h; conv. of CEES reached 100% and selectivity of CEESO ((2-chloroethyl) ethyl sulfoxide) up to 85% after 4 h] outperforms others and can be reused without losing its activity.

19.
Angew Chem Int Ed Engl ; 56(16): 4473-4477, 2017 04 10.
Artigo em Inglês | MEDLINE | ID: mdl-28322483

RESUMO

A novel double-anion complex, H13 [(CH3 )4 N]12 [PNb12 O40 (VV O)2 ⋅(VIV4 O12 )2 ]⋅22 H2 O (1), based on bicapped polyoxoniobate and tetranuclear polyoxovanadate was synthesized, characterized by routine techniques and used in the catalytic decontamination of chemical warfare agents. Under mild conditions, 1 catalyzes both hydrolysis of the nerve agent simulant, diethyl cyanophosphonate (DECP) and selective oxidation of the sulfur mustard simulant, 2-chloroethyl ethyl sulfide (CEES). In the oxidative decontamination system 100 % CEES was transformed selectively to nontoxic 2-chloroethyl ethyl sulfoxide and vinyl ethyl sulfoxide using nearly stoichiometric 3 % aqueous H2 O2 with a turnover frequency (TOF) of 16 000 h-1 . Importantly, the catalytic activity is maintained even after ten recycles and CEES is completely decontaminated in 3 mins without formation of the highly toxic sulfone by-product. A three-step oxidative mechanism is proposed.

20.
Small ; 13(14)2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28151574

RESUMO

Contamination of industrial sewage by organic dye pollutants is one of the most common challenges to the daily life. De-contamination can be achieved by adsorption and photodegradation of the pollutants. However, the former technique is generally limited by the poor loading capacity of the adsorbent and/or the difficulty in its regeneration for reuse, while the latter often suffers from sluggish reaction kinetics and thus requires long reaction time and powerful light source to be successful. Herein, a solution to these challenges by creating nanocomposites featuring porous diamine-functionalized graphene oxide (FGO) impregnated with photocatalytically active polyoxometalates (POMs) is presented. Cross-linking of GO via diamination not only generates porous structures with positively charged interior that attracts and stabilizes the anionic POM guests, but also modulates the GO bandgap. The introduction of POMs improves loading capacity of FGO for cationic dyes and promotes effective separation of electron-hole pair by trapping and transferring photogenerated electron. Thus, the two components act in synergy to result in much improved adsorption of certain common organic dyes as well as enhanced oxidative degradation by both the GO host and the POMs that lead to complete regeneration of the adsorbents without compromising their performance in multiple rounds of reuse.

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