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1.
Nat Commun ; 10(1): 4466, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31578368

RESUMO

Incorporation of mesopores and active sites into metal-organic framework (MOF) materials to uncover new efficient catalysts is a highly desirable but challenging task. We report the first example of a mesoporous MOF obtained by templated electrosynthesis using an ionic liquid as both electrolyte and template. The mesoporous Cu(II)-MOF MFM-100 has been synthesised in 100 seconds at room temperature, and this material incorporates crystal defects with uncoupled Cu(II) centres as evidenced by confocal fluorescence microscopy and electron paramagnetic resonance spectroscopy. MFM-100 prepared in this way shows exceptional catalytic activity for the aerobic oxidation of alcohols to produce aldehydes in near quantitative yield and selectivity under mild conditions, as well as having excellent stability and reusability over repeated cycles. The catalyst-substrate binding interactions have been probed by inelastic neutron scattering. This study offers a simple strategy to create mesopores and active sites simultaneously via electrochemical formation of crystal defects to promote efficient catalysis using MOFs.

2.
Artigo em Inglês | MEDLINE | ID: mdl-31507019

RESUMO

Stable organic nitroxyl radicals are an important class of catalysts for oxidation reactions, but their wide applications are hindered by their steric hinderance, high cost, complex operation and separation procedures. Herein, we reported for the first time that NO2 in DMSO could effectively catalyze the aerobic oxidative cleavage of C(OH)-C bonds to form carboxylic group, and NO2 was in-situ generated by decomposition of nitrates. A diverse range of secondary alcohols were selectively converted to acids in excellent yields in this transition metal-free system without any additives. Preliminary results also indicate its applicability to depolymerize recalcitrant macromolecular lignin. Detail study revealed that NO2 from nitrates promoted the reaction, and NO2 served as hydrogen acceptor and radical initiator for the tandem oxidative reaction.

3.
ACS Appl Mater Interfaces ; 11(34): 30953-30958, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31390522

RESUMO

Metal-organic frameworks (MOFs) have attracted increased research attention in photocatalysis due to their great potential in light harvest and conversion. However, the organic transformations as photocatalyzed by MOFs under mild conditions yet remain a challenge. Herein, three bipyridyl-containing cadmium-organic frameworks Cd(dcbpy) (dcbpy = 2,2'-bipyridine-5,5'-dicarboxylate), Cd(bdc)(bpy) (bdc = 1,4-benzenedicarboxylate; bpy = 2,2'-bipyridyl), and Cd(bdc)(2Me-bpy) (2Me-bpy = 4,4'-dimethyl-2,2'-bipyridyl) were synthesized for the first time. The bpy-containing Cd-MOFs have strong light harvest abilities and suitable photocatalysis energy potentials, making them highly active and selective for the photo-oxidation of benzylamine to N-benzylbenzaldimine under mild conditions, i.e., using atmospheric air as oxidant, at room temperature, and in the absence of any photosensitizer or cocatalyst. It provides an efficient, economical, and green way for the direct oxidation of amines to produce imines.

4.
Nat Commun ; 10(1): 3851, 2019 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-31451700

RESUMO

Efficient electroreduction of carbon dioxide to multicarbon products in aqueous solution is of great importance and challenging. Unfortunately, the low efficiency of the production of C2 products limits implementation at scale. Here, we report reduction of carbon dioxide to C2 products (acetic acid and ethanol) over a 3D dendritic copper-cuprous oxide composite fabricated by in situ reduction of an electrodeposited copper complex. In potassium chloride aqueous electrolyte, the applied potential was as low as -0.4 V vs reversible hydrogen electrode, the overpotential is only 0.53 V (for acetic acid) and 0.48 V (for ethanol) with high C2 Faradaic efficiency of 80% and a current density of 11.5 mA cm-2. The outstanding performance of the electrode for producing the C2 products results mainly from near zero contacting resistance between the electrocatalysts and copper substrate, abundant exposed active sites in the 3D dendritic structure and suitable copper(I)/copper(0) ratio of the electrocatalysts.

5.
Nat Commun ; 10(1): 2980, 2019 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-31278257

RESUMO

Developing highly efficient electrocatalysts based on cheap and earth-abundant metals for CO2 reduction is of great importance. Here we demonstrate that the electrocatalytic activity of manganese-based heterogeneous catalyst can be significantly improved through halogen and nitrogen dual-coordination to modulate the electronic structure of manganese atom. Such an electrocatalyst for CO2 reduction exhibits a maximum CO faradaic efficiency of 97% and high current density of ~10 mA cm-2 at a low overpotential of 0.49 V. Moreover, the turnover frequency can reach 38347 h-1 at overpotential of 0.49 V, which is the highest among the reported heterogeneous electrocatalysts for CO2 reduction. In situ X-ray absorption experiment and density-functional theory calculation reveal the modified electronic structure of the active manganese site, on which the free energy barrier for intermediate formation is greatly reduced, thus resulting in a great improvement of CO2 reduction performance.

6.
Proc Natl Acad Sci U S A ; 116(26): 12654-12659, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-31182598

RESUMO

Synthesis of liquid fuels (C5+ hydrocarbons) via CO2 hydrogenation is very promising. Hydrogenation of CO2 to liquid hydrocarbons usually proceeds through tandem catalysis of reverse water gas shift (RWGS) reaction to produce CO, and subsequent CO hydrogenation to hydrocarbons via Fischer-Tropsch synthesis (FTS). CO2 is a thermodynamically stable and chemically inert molecule, and RWGS reaction is endothermic and needs a higher temperature, whereas FTS reaction is exothermic and is thermodynamically favored at a lower temperature. Therefore, the reported technologies have some obvious drawbacks, such as high temperature, low selectivity, and use of complex catalysts. Herein we discovered that a simple Co6/MnOx nanocatalyst could efficiently catalyze CO2 hydrogenation. The reaction proceeded at 200 °C, which is much lower than those reported so far. The selectivity of liquid hydrocarbon (C5 to C26, mostly n-paraffin) in total product could reach 53.2 C-mol%, which is among the highest reported to date. Interestingly, CO was hardly detectable during the reaction. The in situ Fourier transform infrared characterization and 13CO labeling test confirmed that the reaction was not via CO, accounting for the eminent catalytic results. This report represents significant progress in CO2 chemistry and CO2 transformation.

7.
Chem Commun (Camb) ; 55(48): 6942-6945, 2019 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-31140483

RESUMO

Herein, we developed a fully heterogeneous catalyst (Br-LDH), where the bromide and the hydroxyl are combined in layered double hydroxides (LDH) and cooperate very well in promoting the cycloaddition of CO2 with epoxides. The selectivity and yield of propylene carbonate could reach 95.5% and 92.0%, respectively.

8.
J Am Chem Soc ; 141(9): 4002-4009, 2019 Mar 06.
Artigo em Inglês | MEDLINE | ID: mdl-30739440

RESUMO

Construction of N-substituted pyrrolidones from biomass-derived levulinic acid (LA) via reductive amination is a highly attractive route for biomass valorization. However, realizing this transformation using H2 as the hydrogen source under mild conditions is still very challenging. Herein, we designed porous TiO2 nanosheets-supported Pt nanoparticles (Pt/P-TiO2) as the heterogeneous catalyst. The prepared Pt/P-TiO2 was highly efficient for reductive amination of LA to produce various N-substituted pyrrolidones (34 examples) at ambient temperature and H2 pressure. Meanwhile, Pt/P-TiO2 showed good applicability for reductive amination of levulinic esters, 4-acetylbutyric acid, 2-acetylbenzoic acid, and 2-carboxybenzaldehyde. Systematic studies indicated that the strong acidity of P-TiO2 and the lower electron density of the Pt sites as well as the porous structure resulted in the excellent activity of Pt/P-TiO2.

9.
Nat Commun ; 10(1): 677, 2019 02 08.
Artigo em Inglês | MEDLINE | ID: mdl-30737398

RESUMO

Production of methanol from electrochemical reduction of carbon dioxide is very attractive. However, achieving high Faradaic efficiency with high current density using facile prepared catalysts remains to be a challenge. Herein we report that copper selenide nanocatalysts have outstanding performance for electrochemical reduction of carbon dioxide to methanol, and the current density can be as high as 41.5 mA cm-2 with a Faradaic efficiency of 77.6% at a low overpotential of 285 mV. The copper and selenium in the catalysts cooperate very well for the formation of methanol. The current density is higher than those reported up to date with very high Faradaic efficiency for producing methanol. As far as we know, this is the first work for electrochemical reduction of carbon dioxide using copper selenide as the catalyst.

10.
Angew Chem Int Ed Engl ; 58(14): 4669-4673, 2019 Mar 26.
Artigo em Inglês | MEDLINE | ID: mdl-30729630

RESUMO

Electrochemical reduction of CO2 into energy-dense chemical feedstock and fuels provides an attractive pathway to sustainable energy storage and artificial carbon cycle. Herein, we report the first work to use atomic Ir electrocatalyst for CO2 reduction. By using α-Co(OH)2 as the support, the faradaic efficiency of CO could reach 97.6 % with a turnover frequency (TOF) of 38290 h-1 in aqueous electrolyte, which is the highest TOF up to date. The electrochemical active area is 23.4-times higher than Ir nanoparticles (2 nm), which is highly conductive and favors electron transfer from CO2 to its radical anion (CO2 .- ). Moreover, the more efficient stabilization of CO2 .- intermediate and easy charge transfer makes the atomic Ir electrocatalyst facilitate CO production. Hence, α-Co(OH)2 -supported atomic Ir electrocatalysts show enhanced CO2 activity and stability.

11.
J Nanosci Nanotechnol ; 19(6): 3263-3268, 2019 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-30744752

RESUMO

The environmental friendly biomaterial ß-cyclodextrin (ß-CD) was used for the synthesis of cyclic carbonates from CO2 with epoxides in the presence of quaternary ammonium salts as co-catalyst. The factors affecting the activity of this binary catalyst system, such as reaction temperature, time, CO2 pressure and the mole ratio of reactants, were investigated systematically. The excellent yield of cyclic carbonate (100%) was obtained at 130 °C, 3 MPa after 5 h with the catalyst system of ß-CD/tetrabutylammonium bromine (TBABr). The catalyst system of ß-CD/TBABr can also be applied to a wide substrates of epoxides with good to excellent yield and high selectivity (>99%). Recyclable ability of ß-CD/TBABr can also be detected and there was no significant decline in activity after five recycles. Finally, reaction mechanism was proposed based on the reaction results and literatures.

12.
Chem Commun (Camb) ; 55(7): 925-928, 2019 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-30601484

RESUMO

Stepwise degradation of hydroxyl compounds to aldehydes via successive cleavage of C-C bonds was achieved by using a bimetallic catalytic system (PdCl2 + CuCl) without any ligands and additives. The broad applicability is expanded to a diverse range of aromatic, aliphatic, primary and secondary alcohols, as well as lignin model compounds.

13.
Angew Chem Int Ed Engl ; 58(2): 632-636, 2019 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-30548514

RESUMO

Visible-light-driven photoreduction of CO2 to energy-rich chemicals in the presence of H2 O without any sacrifice reagent is of significance, but challenging. Herein, Eosin Y-functionalized porous polymers (PEosinY-N, N=1-3), with high surface areas up to 610 m2 g-1 , are reported. They exhibit high activity for the photocatalytic reduction of CO2 to CO in the presence of gaseous H2 O, without any photosensitizer or sacrifice reagent, and under visible-light irradiation. Especially, PEosinY-1 derived from coupling of Eosin Y with 1,4-diethynylbenzene shows the best performance for the CO2 photoreduction, affording CO as the sole carbonaceous product with a production rate of 33 µmol g-1 h-1 and a selectivity of 92 %. This work provides new insight for designing and fabricating photocatalytically active polymers with high efficiency for solar-energy conversion.

14.
Sci Adv ; 4(10): eaas9319, 2018 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-30310866

RESUMO

One-pot oxidative transformation of alcohols into esters is very attractive, but metal-based catalysts are used in the reported routes. We discovered that the basic ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM] OAc) could effectively catalyze this kind of reaction using O2 as an oxidant without any other catalysts or additives. The oxidative self-esterification of benzylic alcohols or aliphatic alcohols and cross-esterification between benzyl alcohols and aliphatic alcohols could all be achieved with high yields. Detailed study revealed that the cation with acidic proton and basic acetate anion could simultaneously form multiple hydrogen bonds with the hydroxyl groups of the alcohols, which catalyzed the reaction very effectively. As far as we know, this is the first work to carry out this kind of reaction under metal-free conditions.

15.
Chem Commun (Camb) ; 54(85): 12065-12068, 2018 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-30295688

RESUMO

A method to synthesize bimetallic alloys with tunable morphologies and controlled structural defects was proposed using the characteristics of emulsions tailored by salts. AuPd and PtPd nanowire networks with abundant structural defects exhibited outstanding catalytic performances for oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid, because of the strong ability to generate radicals.

16.
ChemSusChem ; 11(20): 3576-3580, 2018 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-30109779

RESUMO

The development of facile, rapid, low-energy, environmentally benign routes for the synthesis of covalent organic frameworks (COFs) is of great interest. This study concerns the utilization of water containing dissolved CO2 as a solvent for the room-temperature synthesis of COF. The as-synthesized particles, denoted COF-LZU1, combine advantages of good crystallinity, nanoscale size, and high surface area, which suggests promising application as a support for heterogeneous catalysts. Moreover, this versatile CO2 -assisted method is also applicable for the room-temperature synthesis of Cu-COF-LZU1. This method gives rise to new opportunities for fabricating COFs and COF-based materials with different compositions and structures.

17.
Angew Chem Int Ed Engl ; 57(43): 14149-14153, 2018 Oct 22.
Artigo em Inglês | MEDLINE | ID: mdl-30152923

RESUMO

Electrochemical reduction of CO2 to CH3 OH is of great interest. Aerogels have fine inorganic superstructure with high porosity and are known to be exceptional materials. Now a Pd-Cu bimetallic aerogel electrocatalyst has been developed for conversion of CO2 into CH3 OH. The current density and Faradaic efficiency of CH3 OH can be as high as 31.8 mA cm-2 and 80.0 % over the Pd83 Cu17 aerogel at a very low overpotential (0.24 V). The superior performance of the electrocatalyst results from efficient adsorption and stabilization of the CO2 radical anion, high Pd0 /PdII and CuI +Cu0 /CuII ratios, and sufficient Pd/Cu grain boundaries of aerogel nanochains.

18.
ACS Appl Mater Interfaces ; 10(29): 24516-24522, 2018 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-29969233

RESUMO

To develop photocatalysts with desirable compositions and structures for improving the efficiency and selectivity of CO2 conversion to CH4 under mild conditions is of great importance. Here, we design an effective photocatalyst of bimetal (Ag/Pd) nanoalloys supported on nitrogen-doped TiO2 nanosheet for CO2 conversion. Such a novel photocatalyst combines multiple advantages of abundant Ti3+ ions, oxygen vacancies, and substitutional nitrogen that are favorable for catalyzing CO2 reduction. It was found that CO2 could be efficiently transformed to CH4 under mild conditions, i.e., in aqueous solution and at atmospheric pressure and room temperature. The maximum production rate of CH4 can reach 79.0 µmol g-1 h-1. Moreover, the Ag/Pd bimetals supported on N-doped TiO2 nanosheet exhibit high selectivity to CH4. The as-synthesized photocatalyst can be well recycled for CO2 reduction.

19.
Chem Commun (Camb) ; 54(43): 5450-5453, 2018 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-29745397

RESUMO

A non-noble cadmium electrode was synthesized via an electrolysis strategy, which can electroreduce carbon dioxide into carbon monoxide with high selectivity and efficiency. The partial current density for CO can reach up to 59.0 mA cm-2 at a Faradaic efficiency of 99.2% using 1-butyl-3-methylimidazolium hexafluorophosphate/acetonitrile as the electrolyte.

20.
Chem Commun (Camb) ; 54(47): 5984-5987, 2018 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-29790501

RESUMO

Novel porous TiO2@Cu3(BTC)2 composites, which were synthesized using ionic liquids (ILs) as solvents, exhibited excellent activity for photooxidation of styrene to 4-aryl tetralones and promoting the Glaser coupling reaction with O2 under light irradiation. It was discovered that the transformation between Cu2+ and Cu+ was crucial for enhancing the photocatalytic performance.

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