Amino-Acid-Assisted Synthesis of Hollow Hierarchical FER Zeolite with Improved Catalytic Performance.

Hierarchical zeolites are highly-desired catalysts in the petrochemical industry due to their shorter diffusion length, faster diffusion rate, and better accessibility to active acid sites compared with conventional zeolites. Herein, we report a simple amino-acid-assisted method to synthesize urchin-like hollow hierarchical FER zeolites with abundant mesopores and macroporous inner cavities. An amino acid (i. e. L-lysine) is used to facilitate the agglomeration of primary gel nanoparticles. The preferential nucleation and crystal growth at the external surfaces together with the lagged crystallization of the inner core of the agglomerates results in the formation of hollow inner cavities after the exhaustion of interior materials. Thanks to the unique hierarchical structure and more accessible acid sites, the hollow hierarchical FER zeolite exhibits improved catalytic performance over the conventional one in the skeletal isomerization of 1-butene to isobutene.

Hollow STW-Type Zeolite Single Crystals with Aluminum Gradient for Highly Selective Production of p-Xylene from Methanol-Toluene Alkylation.

Zeolites with uniform micropores are important shape-selective catalysts. However, the external acid sites of zeolites have a negative impact on shape-selective catalysis, and the microporosity may lead to serious diffusion limitation. Herein, we report on the direct synthesis of hierarchical hollow STW-type zeolite single crystals with a siliceous exterior. In an alkalinous fluoride medium, the nucleation of highly siliceous STW zeolites takes place first, and the nanocrystals are preferentially aligned on the outer surface of the gel agglomerates to grow into single crystalline shells upon crystallization. The lagged crystallization of the internal Al-rich amorphous gels onto the inner surface of nanocrystalline zeolite shells leads to the formation of hollow cavities in the core of the zeolite crystals. The hollow zeolite single crystals possess a low-to-high aluminum gradient from the surface to the core, resulting in an intrinsic inert external surface, and exhibit superior catalytic performance in toluene methylation reactions.

Synthesis and Characterization of A Stable Extra-Large-Pore Zeolite with 15×12×12 Member-Ring Channels.

Extra-large-pore zeolites have great application potential in various industrial fields, such as oil refinery, fine chemicals and biomass processing. Herein, we report the synthesis of an extra-large-pore germanosilicate zeolite (named NUD-13) by using an easily obtained aromatic organic cation 1,2-dimethyl-3-propyl-benzimidazolium as organic structure-directing agents. NUD-13 possesses a rare 15-member ring extra-large-pore channel intersecting with two elliptical 12-member ring channels, which is isostructural to germanosilicate zeolite GeZA synthesized by using triphenylsulfonium. The germanium in NUD-13 can be partially substituted by acid treatment to obtain stable high silica zeolite. In addition, aluminium is added into the framework of NUD-13 during the post-synthesis treatment process, which provides a foundation for catalytic application.

Direct Synthesis of An Aluminosilicate POS Zeolite with Intersecting 12×11×11-Member-Ring Pore Channels by Using a Designed Organic Structure-Directing Agent.

Large and extra-large pore zeolites have been widely applied in industrial areas as catalysts, adsorbents, etc. Among them, silica and/or aluminosilicate zeolites have been attracted great attention due to their excellent hydrothermal stability and strong acidity. However, a great deal of zeolite structures are still not available in the form of silica and/or aluminosilicate. Herein, we report the synthesis of pure silica and aluminosilicate large-pore zeolites, denoted as NUD-14 and Al-NUD-14, respectively, by using a designed cation 1-ethyl-4-phenylpyridinium as an organic structure-directing agent (OSDA). NUD-14 has an intersecting 12×11×11-member ring pore system, which is isostructural to the germanosilicate PUK-16 zeolite with a POS topology. The OSDAs can be completely removed from the framework by calcination. NUD-14 and Al-NUD-14 possess excellent acid and hydrothermal stabilities, superior to the germanosilicate POS zeolite. The incorporation of Al into the zeolite framework makes the Al-NUD-14 zeolite possess medium and strong acidities. The successful synthesis of NUD-14 consisting of a rare odd-member ring pore structure may provide a platform for interesting size- and shape-selective catalytic applications.

Solvent-Induced Growth of Free-Standing 2D Si Nanosheets.

2D Si nanomaterials draw great interest owing to their fascinating properties and potential applications in electronic devices, catalysts, and energy storage and conversion devices. However, high-quality and large-scale synthesis of Si nanosheets remains a big challenge, despite the limited reports on their preparations via chemical exfoliation of layered Zintl silicide, magnesiothermic reduction of layered silicon oxide, and chemical vapor deposition. In this work, a facile, solution method to produce free-standing Si nanosheets in high yields and low cost, based on the reaction of commercial magnesium powder with trichlorosilane and tripropylamine in dichloromethane under mild conditions, is reported. The prepared Si nanosheets have an average thickness of ≈2 nm and show photoluminescence. Experiments demonstrate that the key to the formation of Si nanosheets is the use of dichloromethane as a solvent. This method can be used to prepare Si nanosheets in large scale for various potential applications and possibly Si crystals with specific crystal morphology.

Synthesis, Structure and Properties of an Extra-Large-Pore Aluminosilicate Zeolite NUD-6.

Pure silica zeolites possessing uniform micropores, large surface area and high thermal and chemical stability have been widely studied and used in the fields of fine chemicals and oil industry. The incorporation of aluminium into the framework of silica zeolites changes their properties, making them more industrially useful as adsorbents and catalysts. Herein, we report the synthesis and characterization of an extra-large-pore aluminosilicate zeolite NUD-6 with a 16-membered-ring pore channel. Aluminium was directly incorporated into the zeolite NUD-6 framework, as confirmed by 27 Al MAS NMR studies and ammonia temperature-programmed desorption probes. Al-NUD-6 was not stable when heated at 550 °C to remove the organic templates. However, the organic templates in Al-NUD-6 could be removed by oxidation in nitric acid at room temperature. The obtained Al-NUD-6H retained the crystalline structure and possessed both micropores and mesopores despite the occurrence of severe structural distortions due to the presence of the corner-sharing Q3 Si2 O7 units. The incorporation of aluminium resulted in both medium and strong acid sites in Al-NUD-6H, and could facilitate its use in adsorption and catalysis.

An Extra-Large-Pore Pure Silica Zeolite with 16×8×8-Membered Ring Pore Channels Synthesized using an Aromatic Organic Directing Agent.

Extra-large-pore zeolites for processing large molecules have long been sought after by both the academia and industry. However, the synthesis of these materials, particularly extra-large-pore pure silica zeolites, remains a big challenge. Herein we report the synthesis of a new extra-large-pore silica zeolite, designated NUD-6, by using an easily synthesized aromatic organic cation as structure-directing agent. NUD-6 possesses an intersecting 16×8×8-membered ring pore channel system constructed by four-connected (Q4 ) and unusual three-connected (Q3 ) silicon species. The organic cations in NUD-6 can be removed in nitric acid to yield a porous material with high surface area and pore volume. The synthesis of NUD-6 presents a feasible means to prepare extra-large pore silica zeolites by using assembled aromatic organic cations as structure-directing agents.

Solution Synthesis of Porous Silicon Particles as an Anode Material for Lithium Ion Batteries.

Nanostructured silicon-based materials with porous structures have recently been found to be impressive anode materials with high capacity and cycling performance for lithium-ion batteries. However, the current methods of preparing porous silicon have generally been confronted with the requirement for multiple steps and complex synthesis. In the present study, porous silicon with high surface area was prepared by using a high yielding and simple reaction in which commercial magnesium powder readily reacts with HSiCl3 with the help of an amine catalyst under mild conditions. The obtained porous silicon was coated with a nitrogen-doped carbon layer and used as the anode for lithium-ion batteries. The porous Si-carbon nanocomposites exhibited excellent cycling performance with a retained discharge capacity of 1300 mA h g-1 after 200 cycles at 1 A g-1 and a discharge capacity of 750 mA h g-1 at a current density of 2 A g-1 after 250 cycles. Remarkably, the Coulombic efficiency was maintained at nearly 100 % throughout the measurements.

A Stable Extra-Large-Pore Zeolite with Intersecting 14- and 10-Membered-Ring Channels.

The development of inorganic frameworks with extra-large pores (larger than 12-membered rings) has attracted considerable attention because of their potential applications in catalysis, the separation of large molecules, and so forth. We herein report the synthesis of the new extra-large-pore zeolite NUD-2 by using the supramolecular self-assembly of simple aromatic organic cations as structure-directing agents (SDAs). NUD-2 is a high-silicon-content germanosilicate with interconnecting 14×10-membered-ring channels. The SDAs in NUD-2 can be removed by calcination in air at 550 °C to yield permanent pores with a BET surface area of 500 m(2) g(-1) . Both germanium and organic cations in NUD-2 can also be removed by treatment with acid at lower temperature, thus not only affording recycling of germanium and SDAs, but also providing a highly stable siliceous zeolite. In addition, aluminum ions can be incorporated into the framework of NUD-2. The NUD-2 structure is yet another extra-large-pore zeolite synthesized by using the supramolecular self-assembling templating approach, thus demonstrating that this approach is a general and applicable strategy for synthesis of new large- and extra-large-pore zeolites.

Highly Stable Mesoporous Zirconium Porphyrinic Frameworks with Distinct Flexibility.

The construction of highly stable metal-porphyrinic frameworks (MPFs) is appealing as these materials offer great opportunities for applications in artificial light-harvesting systems, gas storage, heterogeneous catalysis, etc. Herein, we report the synthesis of a novel mesoporous metal-porphyrinic framework (denoted as NUPF-1) and its catalytic properties. NUPF-1 is constructed from a new porphyrin linker and a Zr6 O8 structural building unit, possessing an unprecedented doubly interpenetrating scu net. The structure exhibits not only remarkable chemical and thermal stabilities, but also a distinct structural flexibility, which is seldom seen in metal-organic framework (MOF) materials. By the merit of high chemical stability, NUPF-1 could be easily post-metallized with [Ru3 (CO)12 ], and the resulting {NUPF-1-RuCO} is catalytically active as a heterogeneous catalyst for intermolecular C(sp(3) )-H amination. Excellent yields and good recyclability for amination of small substrates with various organic azides have been achieved.

Preparation of uniform Si nanoparticles for high-performance Li-ion battery anodes.

Nanostructured silicon has attracted a great deal of attention as an excellent anode material for Li ion batteries (LIBs). However, the use of Si nanomaterials in LIBs is severely hindered by their preparative methods owing to the high cost, low yield, and harsh synthetic conditions. Herein, we report a new method for the synthesis of uniform Si nanocrystals based on the magnesiothermic reduction of natural attapulgite clay. The obtained Si nanocrystals with a uniform size of ca. 10 nm are coated with polypyrrole (denoted ppy@Si) and show excellent electrochemical performance as anode materials for LIBs. After charging-discharging for 200 cycles at a current density of 0.6 A g(-1), the specific capacity value of the ppy@Si anode is ∼954 mA h g(-1). Because of the abundance of attapulgite, the obtained silicon nanoparticles can be exploited as a practical anode material for high-performance Li-ion batteries.

An extra-large-pore zeolite with intersecting 18-, 12-, and 10-membered ring channels.

Zeolites with extra-large pores have attracted great attention because of their important applications such as in hydrocracking, catalysis, and separation of large molecules. Despite much progress has been made during the past decades, the synthesis of these materials remains a big challenge. A new extra-large-pore zeolite NUD-1 (Nanjing University Du's group zeolite no. 1) is synthesized by using an approach based on supramolecular self-assemblies of small aromatic organic cations as structure-directing agents. NUD-1 possesses interconnecting 18-, 12-, and 10-membered ring channels, built from the same building units as those of ITQ-33 and ITQ-44. There coexist single 3-membered ring, double-3-membered ring and double-4-membered ring secondary building units in NUD-1, which have not been seen in any other zeolites.

Research on the identification and evolution of health industry policy instruments in China.

The application of health industry policies could be discovered more quickly and comprehensively through the automated identification of policy tools, which could provide references for the formulation, implementation, and optimization of subsequent policies in each province. This study applies the Bidirectional Encoder Representation from Transformer (BERT) model to identify policy tools automatically, utilizes Focal Loss to reduce the unbalance of a dataset, and analyzes the evolution of policy tools in each province, which contains time, space, and topic. The research demonstrates that the BERT model can improve the accuracy of classification, that supply and environment policy tools are more prevalent than demand tools, and that policy instruments are organized similarly in four major economic regions. Moreover, the policy's attention to topics related to healthcare, medicine, and pollution has gradually shifted to other topics, and the extent of policy attention continues to be concentrated on the health service industry, with less attention paid to the manufacturing industry from the keywords of the various topics.

In Situ Copper Coating on Silicon Particles Enables Long Durable Anodes in Lithium-Ion Batteries.

Addressing the significant obstacles of volume expansion and inadequate electronic conductivity in silicon-based anode materials during lithiation is crucial for achieving a long durable life in lithium-ion batteries. Herein, a high-strength copper-based metal shell is coated in situ onto silicon materials through a chemical combination of copper citrate and Si-H bonds and subsequent heat treatment. The formed Cu and Cu3Si shell effectively mitigates the mechanical stress induced by volume expansion during lithiation, strengthens the connection with the copper substrate, and facilitates electron transfer and Li+ diffusion kinetics. Consequently, the composite exhibits a reversible specific capacity of 1359 mA h g-1 at 0.5 A g-1 and maintains a specific capacity of 837 mA h g-1 and an 83.5% capacity retention after 400 cycles at 1 A g-1, surpassing similar reports on electrochemical stability. This facile copper plating technique on silicon surfaces may be used to prepare high-performance silicon-based anodes or functional composites in other fields.

A fluoride-free siliceous STW-type zeolite synthesized using a designed organic structure-directing agent.

A pure silica STW zeolite is synthesized with no impurities under a wide range of synthesis conditions with and without fluoride by using easily available 1-methyl-1,5-diazabicyclo[4.3.0]non-5-ene (MDBN) as a template. MDBN having an appropriate size and geometry fits well in the STW cage, leading to its high specificity in structure-directing formation of zeolite STW.

One-step synthesis of uniformly distributed SiOx-C composites as stable anodes for lithium-ion batteries.

SiOx is one of the most promising anode materials for lithium-ion batteries (LIBs), due to its high theoretical capacity and low cost. However, the huge volume expansion and low electron/ion diffusion rate hinder its further commercial applications. Herein, a simple molecular polymerization method is developed to synthesize N,P co-doped SiOx-C composites (denoted as SiOx-C@CNT), in which SiOx and carbon are uniformly dispersed at the atomic level, and the embedded carbon nanotubes improve the lithium ion diffusion kinetics. Benefiting from the unique structure, the SiOx-C@CNT composites exhibit a high reversible capacity of 848 mA h g-1 at 0.1 A g-1 and long cycling stability (84.0% capacity retention after 1500 cycles). More impressively, the LiCoO2∥SiOx-C@CNT full battery also exhibits stable cycle life (only 4.7% capacity loss after 300 cycles at 1 C). These results show the application potential of the SiOx-C@CNT anode in LIBs.

Structure-direction towards the new large pore zeolite NUD-3.

The new zeolite NUD-3 possesses a three-dimensional system of large pore channels that is topologically identical to those of ITQ-21 and PKU-14. However, the three zeolites have distinctly different frameworks: a particular single 4-membered ring inside the denser portion of the zeolite is missing in PKU-14, disordered in ITQ-21 and fully ordered in NUD-3. We document these differences and use molecular simulations to unravel the mechanism by which a particular structure directing agent dication, 1,1'-(1,2-phenylenebis(methylene))bis(3-methylimidazolium), is able to orient this inner ring.

Porous coordination polymers of transition metal sulfides with PtS topology built on a semirigid tetrahedral linker.

Four novel porous metal sulfide coordination polymers, [M(tpom)S(x)(SH)(y)] x z(H(2)O) (metal-sulfide frameworks, denoted MSF-n, n = 1, Cd; 2, Mn; 3, Fe; 4, Co; x = 0, y = 2 for 1, 2, and 4 and x = 0.54, y = 1.46 for 3), were solvothermally prepared by using a quadridentate linker, tetrakis(4-pyridyloxymethylene)methane (tpom), in the presence of organic sulfur compound under an acidic conditions. MSF-n (n = 1-4) is isostructural and built upon the tetrahedral tpom linker and square planar MS(x)(SH)(y) unit, which form a binodal 4,4-connected porous framework with a 2-fold interpenetrated 4(2)8(4)-pts net. With rectangular pore channels of about 5 x 6 A(2) (interatomic distances between the nearest protruding H atoms across) running along both the crystallographic a and b directions, MSF-n possesses permanent porosity with a BET surface area of 575, 622, 617, and 767 m(2)/g for MSF-1, -2, -3, and -4, respectively, as estimated from N(2) adsorption measurements. MSF-n (n = 1-4) has hydrogen storage capacities of 1.03, 1.37, 1.29, and 1.58 wt % at 77 K and 1 atm, respectively, each corresponding to 2.0 H(2) molecules per unit cell. In addition, MSF-n (n = 1-4) can adsorb 24.1, 25.0, 21.6, and 24.1 wt % of carbon dioxide and 6.0, 6.1, 5.6, and 6.4 wt % of methane, respectively, at room temperature and 20 atm.

One-pot solution synthesis of carbon-coated silicon nanoparticles as an anode material for lithium-ion batteries.

Carbon-coated silicon nanoparticles were in situ synthesized via a facile one-pot solution synthesis method, which delivered an excellent cycling performance with a retained discharge capacity of 1120 mA h g-1 and almost no capacity decay after 500 cycles at 2 A g-1 when evaluated as an anode material in lithium ion batteries.

Synthesis and characterization of a layered aluminosilicate NUD-11 and its transformation to a 3D stable zeolite.

Aluminosilicate zeolites are a well-known class of crystalline materials that have wide applications in various industrial fields due to their selective adsorption, acidic sites, and stable hydrothermal stability. Great efforts have been devoted to discovering new zeolite structures. As one of the effective methods, layered silicates have been used as precursors to produce stable zeolites through topotactic transformation. Herein, a new layered aluminosilicate, named NUD-11, was hydrothermally synthesized using N,N-dimethylbenzimidazolium as the structure directing agent (SDA). It was then converted into a stable crystalline zeolite by linking the interlayer Si-OH groups with a silylation agent, diethoxymethylsilane. Studies showed that the resulting NUD-11S consisted of alkylsilicate -O-Si(CH3)2-O- linkages between the adjacent layers to form interconnecting 10- and 12-membered ring channels. The calcined NUD-11S possessed micropores of 0.74 nm and 1.2 nm in diameter with a large specific surface area of 314 m2 g-1. The abundant microporosity would make NUD-11S useful as adsorbents or catalysts.