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1.
Chem Commun (Camb) ; 56(73): 10631-10641, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32930275

RESUMO

Nature has long been a dominant source of inspiration in the area of chemistry, serving as prototypes for the design of materials with proficient performance. In this Feature article, we present our efforts to explore porous organic polymers (POPs) as a platform for the construction of biomimetic materials to enable new technologies to achieve efficient conversions and molecular recognition. For each aspect, we first present the chemical basis of nature, followed by depicting the principles and design strategies involved for functionalizing POPs along with a summary of critical requirements for materials, culminating in a demonstration of unique features of POPs. Our endeavours in using POPs to address the fundamental scientific problems related to biomimetic catalysis and adsorption are then illustrated to show their enormous potential and capabilities for applications ranging from concerted catalysis to radionuclide sequestration. To conclude, we present a personal perspective on the challenges and opportunities in this emerging field.

2.
J Am Chem Soc ; 142(38): 16429-16436, 2020 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-32862644

RESUMO

Nonoxidative dehydrogenation is promising for production of light olefins from shale gas, but current technology relies on precious Pt or toxic Cr catalysts and suffers from thermodynamically oriented coke formation. To solve these issues, the earth-abundant iron catalyst is employed, where Fe species are effectively modulated by siliceous zeolite, which is realized by the synthesis of Fe-containing MFI siliceous zeolite in the presence of ethylenediaminetetraacetic sodium (FeS-1-EDTA). Catalytic tests in ethane dehydrogenation show that this catalyst has a superior coke resistance in a 200 h run without any deactivation with extremely high activity and selectivity (e.g., 26.3% conversion and over 97.5% selectivity to ethene in at 873 K, close to the thermodynamic equilibrium limitation). Multiple characterizations demonstrate that the catalyst has uniformly and stably isolated Fe sites, which improves ethane dehydrogenation to facilitate the fast desorption of hydrogen and olefin products in the zeolite micropores and hinders the coke formation, as also identified by density functional calculations.

3.
ChemSusChem ; 2020 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-32851788

RESUMO

Strong metal-support interactions (SMSI) could improve the performance of nanoparticle catalysts through the electronic and geometric modulation of the reducible metal oxide supports. Here, SMSI is demonstrated to occur for catalysts with non-oxide carrier, such as NbOPO4 -supported Rh nanoparticles, under reduction treatment at low temperature. During CO2 hydrogenation, this Rh/NbOPO4 catalyst with SMSI exhibits impressive CO selectivity at high CO2 conversion in a wide temperature range with hindered methanation. For example, over 98.9 % CO selectivity was obtained with 39.9 % CO2 conversion at 500 °C. Mechanism investigations demonstrate that the SMSI results in the formation of a metal-support interface with weaker CO adsorption than the metallic Rh sites, thus accelerating the CO desorption, which hinders deep hydrogenation. Rh nanoparticles with small diameter of about 1.1 nm is sinter-resistant with unchanged performance during a long-period test. This work might extend the investigation of SMSI from oxides to phosphate supports, which helps optimizing the selectivity and stability of metal nanoparticle catalysts.

4.
Chemistry ; 2020 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-32515846

RESUMO

Unlike conventional aluminosilicate zeolites synthesized in alkaline media, aluminophosphate molecular sieves (AlPOs) have always been prepared under acidic conditions in the past three decades; this has been regarded as one of essential factors for synthesis, except for the case of silica-substituted analogues (SAPOs). For the first time, we demonstrate herein a simple and generalized route for synthesizing various types of aluminophosphate molecular sieves in alkaline media. A series of aluminophosphate sieves and their analogues have been prepared with different quaternary ammonium cations as structure-directing agents in this manner. The above successes have extended the systematic media from acidic or neutral to alkaline for the preparation of a series of aluminophosphate molecular sieves, which possibly open an alternative route for the synthesis of aluminophosphate molecular sieves.

5.
Artigo em Inglês | MEDLINE | ID: mdl-32453899

RESUMO

There are a large number of zeolites, such as ITH, that cannot be prepared in the aluminosilicate form. Now, the successful synthesis of aluminosilicate ITH zeolite using a simple cationic oligomer as an organic template is presented. Key to the success is that the cationic oligomer has a strong complexation ability with aluminum species combined with a structural directing ability for the ITH structure similar to that of the conventional organic template. The aluminosilicate ITH zeolite has very high crystallinity, nanosheet-like crystal morphology, large surface area, fully four-coordinated Al species, and abundant acidic sites. Methanol-to-propylene (MTP) tests reveal that the Al-ITH zeolite shows much higher selectivity for propylene and longer lifetime than commercial ZSM-5. FCC tests show that Al-ITH zeolite is a good candidate as a shape-selective FCC additive for enhancing propylene and butylene selectivity.

6.
Nat Commun ; 11(1): 1722, 2020 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-32238812

RESUMO

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

7.
Dalton Trans ; 2020 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-32307488

RESUMO

With the merits of the accelerated crystallization process, high volume yields, and reduced waste production, solvent-free syntheses give new opportunities for the fabrication of zeolites. In this Frontier, a background overview is provided, consisting of a brief introduction of challenges in traditional zeolite syntheses and how solvent-free syntheses provide the right combination of properties for achieving a more sustainable route. Next, recent advancements in zeolites synthesized under solvent-free conditions are exemplified along with discussions about the strategies and principles involved. Finally, the remaining challenges and opportunities for this synthetic route are outlined.

8.
Science ; 367(6474): 193-197, 2020 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-31919221

RESUMO

Selective partial oxidation of methane to methanol suffers from low efficiency. Here, we report a heterogeneous catalyst system for enhanced methanol productivity in methane oxidation by in situ generated hydrogen peroxide at mild temperature (70°C). The catalyst was synthesized by fixation of AuPd alloy nanoparticles within aluminosilicate zeolite crystals, followed by modification of the external surface of the zeolite with organosilanes. The silanes appear to allow diffusion of hydrogen, oxygen, and methane to the catalyst active sites, while confining the generated peroxide there to enhance its reaction probability. At 17.3% conversion of methane, methanol selectivity reached 92%, corresponding to methanol productivity up to 91.6 millimoles per gram of AuPd per hour.

9.
J Am Chem Soc ; 141(45): 18318-18324, 2019 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-31644275

RESUMO

A large amount of zeolite structures are still not synthetically available or not available in the form of aluminosilicate currently. Despite significant progress in the development of predictive concepts for zeolite synthesis, accessing some of these new materials is still challenging. One example is the IWR structure as well. Despite successful synthesis of Ge-based IWR zeolites, direct synthesis of aluminosilicate IWR zeolite is still not successful. In this report we show how a suitable organic structure directing agent (OSDA), through modeling of an OSDA/zeolite cage interaction, could access directly the aluminum-containing IWR structure (denoted as COE-6), which might allow access to new classes of materials and thus open opportunities in valuable chemical applications. The experimental results reveal that the COE-6 zeolites with a SiO2/Al2O3 ratio as low as 30 could be obtained. Very interestingly, the COE-6 zeolite has much higher hydrothermal and thermal stabilities than those of the conventional Ge-Al-IWR zeolite. In methanol-to-propylene (MTP) reaction, the COE-6 zeolite exhibits excellent selectivity for propylene, offering a potential catalyst for MTP reaction in the future.

10.
Adv Mater ; 31(50): e1901905, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31478282

RESUMO

Supported metal nanoparticles are widely used as catalysts in the industrial production of chemicals, but still suffer from deactivation because of metal leaching and sintering at high temperature. In recent years, serious efforts have been devoted to developing new strategies for stabilizing metal nanoparticles. Recent developments for preparing sinter-resistant metal-nanoparticle catalysts via strong metal-support interactions, encapsulation with oxide or carbon layers and within mesoporous materials, and fixation in zeolite crystals, are briefly summarized. Furthermore, the current challenges and future perspectives for the preparation of highly efficient and extraordinarily stable metal-nanoparticle-based catalysts, and suggestions regarding the mechanisms involved in sinter resistance, are proposed.

11.
Nat Commun ; 10(1): 3059, 2019 07 11.
Artigo em Inglês | MEDLINE | ID: mdl-31296873

RESUMO

Precise control of the outer-sphere environment around the active sites of heterogeneous catalysts to modulate the catalytic outcomes has long been a challenge. Here, we demonstrate how this can be fulfilled by encapsulating catalytic components into supramolecular capsules, used as building blocks for materials synthesis, whereby the microenvironment of each active site is tuned by the assembled wall. Specifically, using a cationic template equipped with a polymerizable functionality, anionic ligands can be encapsulated by ion pair-directed supramolecular assembly, followed by construction into porous frameworks. The hydrophilic ionic wall enables reactions to be achieved in water that usually requires organic solvents and also facilitates the enrichment of the substrate into the hydrophobic pocket, leading to superior catalytic performances as demonstrated by the industrially relevant hydroformylation. Remarkably, the formation of the supramolecular assembly and catalyst encapsulation further engenders reaction selectivity, which reaches an even greater extent after construction of the porous framework.

12.
Angew Chem Int Ed Engl ; 58(35): 12138-12142, 2019 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-31283076

RESUMO

Currently, the synthesis of pure silica zeolites always requires the presence of organic structure-directing agents (OSDAs), which direct the assembly pathway and ultimately fill the pore space. A sustainable route is now reported for synthesizing pure silica zeolites in the absence of OSDAs from a combined strategy of zeolite seeding and alcohol filling, where the zeolite seeds direct crystallization of zeolite crystals from amorphous silica, while the alcohol is served as pore filling in the zeolites. Very importantly, the alcohol could be fully washed out from zeolite pores by water at room temperature, which completely avoids calcination at high temperature for removal of OSDAs in the synthesis of pure silica zeolites.

13.
Chem Commun (Camb) ; 55(62): 9180-9183, 2019 Aug 11.
Artigo em Inglês | MEDLINE | ID: mdl-31305813

RESUMO

Herein, we show that by following molecular engineering of the inter-site distance between the two functionalities in porous organic materials, it is possible to enable them to work in a concerted manner. Specifically, the activity can be amplified by the placement of the hydroxyl group in the meta position of the phosphonium salts in the representative cycloaddition of epoxides and CO2.

14.
ACS Appl Mater Interfaces ; 11(26): 23112-23117, 2019 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-31252486

RESUMO

For the first time, SSZ-39 zeolite has been directly prepared using conventional colloidal silica and sodium aluminate instead of using FAU zeolite as the raw material in the alkaline media. The adjustment of the Si/Al ratios in the starting materials to the suitable values is a key factor to prepare the aluminosilicate SSZ-39 zeolite. Various characterizations (for instance, X-ray diffraction, scanning electron microscopy, nitrogen sorption, solid 27Al NMR, and NH3-temperature-programmed desorption) display that the aluminosilicate SSZ-39 zeolite owns high crystallinity, uniform cuboid morphology, large surface area, four-coordinated aluminum species, and strong acidic sites. Inductively coupled plasma analysis shows that the SiO2/Al2O3 ratios of the SSZ-39 products are ranged from 12.8 to 16.8. Considering the special framework of the SSZ-39 zeolite, the yield of this synthesis is not higher than 21.3%. Moreover, the catalytic performance of Cu-SSZ-39 catalyst synthesized from this route is excellent in the selective catalytic reduction of NO x with NH3 (NH3-SCR).

15.
J Am Chem Soc ; 141(21): 8482-8488, 2019 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-31063372

RESUMO

Supported rhodium nanoparticles (NPs) are well-known for catalyzing methanation in CO2 hydrogenation. Now we demonstrate that the selectivity in this process can be optimized for CO production by choice of molecular sieve crystals as supports. The NPs are enveloped within the crystals with controlled nanopore environments that allow tuning of the catalytic selectivity to minimize methanation and favor the reverse water-gas shift reaction. Pure silica MFI (S-1)-fixed rhodium NPs exhibited maximized CO selectivity at high CO2 conversions, whereas aluminosilicate MFI zeolite-supported rhodium NPs displayed high methane selectivity under the equivalent conditions. Strong correlations were observed between the nanoporous environment and catalytic selectivity, indicating that S-1 minimizes hydrogen spillover and favors fast desorption of CO to limit deep hydrogenation. Materials in this class appear to offer appealing opportunities for tailoring selective supported catalysts for a variety of reactions.

16.
Angew Chem Int Ed Engl ; 58(26): 8670-8675, 2019 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-30957347

RESUMO

Herein, we show how the spatial environment in the functional pores of covalent organic frameworks (COFs) can be manipulated in order to exert control in catalysis. The underlying mechanism of this strategy relies on the placement of linear polymers in the pore channels that are anchored with catalytic species, analogous to outer-sphere residue cooperativity within the active sites of enzymes. This approach benefits from the flexibility and enriched concentration of the functional moieties on the linear polymers, enabling the desired reaction environment in close proximity to the active sites, thereby impacting the reaction outcomes. Specifically, in the representative dehydration of fructose to produce 5-hydroxymethylfurfural, dramatic activity and selectivity improvements have been achieved for the active center of sulfonic acid groups in COFs after encapsulation of polymeric solvent analogues 1-methyl-2-pyrrolidinone and ionic liquid.

17.
J Am Chem Soc ; 141(7): 2975-2983, 2019 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-30677301

RESUMO

Classical strong metal-support interactions (SMSI), which play a crucial role in the preparation of supported metal nanoparticle catalysts, is one of the most important concepts in heterogeneous catalysis. The conventional wisdom for construction of classical SMSI involves in redox treatments at high-temperatures by molecular oxygen or hydrogen, sometimes causing sintered metal nanoparticles before SMSI formation. Herein, we report that the aforementioned issue can be effectively avoided by a wet-chemistry methodology. As a typical example, we demonstrate a new concept of wet-chemistry SMSI (wcSMSI) that can be constructed on titania-supported Au nanoparticles (Au/TiO2-wcSMSI), where the key is to employ a redox interaction between Auδ+ and Ti3+ precursors in aqueous solution. The wcSMSI is evidenced by covering Au nanoparticles with the TiO x overlayer, electronic interaction between Au and TiO2, and suppression of CO adsorption on Au nanoparticles. Owing to the wcSMSI, the Au-TiO x interface with an improved redox property is favorable for oxygen activation, accelerating CO oxidation. In addition, the oxide overlayer efficiently stabilizes the Au nanoparticles, achieving sinter-resistant Au/TiO2-wcSMSI catalyst in CO oxidation.

18.
ChemSusChem ; 11(22): 3965-3974, 2018 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-30350924

RESUMO

Construction of efficient interfaces to improve the performance of supported metal catalysts is a challenging but effective technique. A newly synthesized catalyst with layered cobalt oxide on the surface of titania (layer-CoOx /TiO2 ) is highly selective towards the aerobic oxidation of C-H bonds in a series of hydrocarbons under sustainable conditions. The layer-CoOx /TiO2 easily outperforms the state-of-the-art noble metal catalysts and homogeneous cobalt salts used in industry. In-depth structural and functional characterization reveal that the layer-CoOx /TiO2 readily reacts with O2 for the adsorption and activation of C-H bonds. The layered structure of CoOx can maximize the interfacial effect of CoOx /TiO2 leading to a good performance for the oxidation of C-H bonds.

19.
ACS Appl Mater Interfaces ; 10(39): 33214-33220, 2018 Oct 03.
Artigo em Inglês | MEDLINE | ID: mdl-30203642

RESUMO

Modern methodologies for synthesizing zeolites typically involve the employment of costly organic structure-directing agents. Herein, we report the design synthesis of aluminosilicate zeolite with ITE structure using an inexpensive nickel-amine complex (nickel-pentaethylenexamine) as a novel structure-directing agent. Characterizations including X-ray diffraction, scanning electron microscopy, N2 sorption isotherms, and 27Al magic-angle spinning NMR techniques show that the ITE zeolite has high crystallinity, perfect crystals, large surface area, and abundant aluminum species in the framework. More importantly, catalytic tests on the hydrogenation of CO2 into methane show that the Ni-ITE zeolite exhibits better catalytic performance than aluminosilicate-supported and silica-supported nickel catalysts. Obviously, the use of nickel-amine complex offers an alternative and facile way to synthesize aluminosilicate zeolites.

20.
Nat Commun ; 9(1): 3236, 2018 08 13.
Artigo em Inglês | MEDLINE | ID: mdl-30104623

RESUMO

Chemical transformations are highly sensitive toward changes in the solvation environment and solvents have long been used to control their outcome. Reactions display unique performance in solvents like ionic liquids or DMSO, however, isolating products from them is cumbersome and energy-consuming. Here, we develop promising alternatives by constructing solvent moieties into porous materials, which in turn serve as platforms for introducing catalytic species. Due to the high density of the solvent moieties, these porous solid solvents (PSSs) retain solvation ability, which greatly influences the performance of incorporated active sites via concerted non-covalent substrate-catalyst interactions. As a proof-of-concept, the -SO3H-incorporated PSSs exhibit high yields of fructose to 5-hydroxymethylfurfural in THF, which exceeds the best results reported using readily separable solvents and even rivals those in ionic liquids or DMSO. Given the wide application, our strategy provides a step forward towards sustainable synthesis by eliminating the concerns with separation unfriendly solvents.

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