Jihong Yu

Preparation of Inorganic Materials Using Ionic Liquids

Conventional synthesis of inorganic materials relies heavily on water and organic solvents. Alternatively, the synthesis of inorganic materials using, or in the presence of, ionic liquids represents a burgeoning direction in materials chemistry. Use of ionic liquids in solvent extraction and organic catalysis has been extensively studied, but their use in inorganic synthesis has just begun. Ionic liquids are a family of non-conventional molten salts that can act as templates and precursors to inorganic materials, as well as solvents. They offer many advantages, such as negligible vapor pressures, wide liquidus ranges, good thermal stability, tunable solubility for both organic and inorganic molecules, and much synthetic flexibility. In this Review, the use of ionic liquids in the preparation of several categories of inorganic and hybrid materials (i.e., metal structures, non-metal elements, silicas, organosilicas, metal oxides, metal chalcogenides, metal salts, open-framework structures, ionic liquid-functionalized materials, and supported ionic liquids) is summarized. The status quo of the research field is assessed, and some future perspectives are furnished.

Extra-large-pore zeolites: bridging the gap between micro and mesoporous structures.

The conditions required to produce zeolites with low framework density and extra-large pores are discussed. Correlations between framework stability and geometrical and topological descriptors are presented. An attempt has been made to rationalize the synthesis of extra-large-pore zeolites in terms of the synthesis mechanism, the directing effect of the organic structure directing agent (OSDA), the framework atoms, and the gel concentration. Extra-large-pore zeolites, including the recently discovered chiral mesoporous ITQ-37, are described and their catalytic and adsorption properties discussed. Finally, strategies are presented for the preparation of extra-large-pore zeolites with different pore topologies that can fulfill pre-established catalytic and adsorption targets.

Synthesis and Structure Determination of the Hierarchical Meso-Microporous Zeolite ITQ-43

A zeolite with microporous channels (6 to 7 angstrom diameter) and mesoporous channels (~2-nanometer diameter) was made. The formation of mesopores in microporous zeolites is generally performed by postsynthesis acid, basic, and steam treatments. The hierarchical pore systems thus formed allow better adsorption, diffusion, and reactivity of these materials. By combining organic and inorganic structure-directing agents and high-throughput methodologies, we were able to synthesize a zeolite with a hierarchical system of micropores and mesopores, with channel openings delimited by 28 tetrahedral atoms. Its complex crystalline structure was solved with the use of automated diffraction tomography.

Insight into the construction of open-framework aluminophosphates

Over the past twenty five years, a class of open-framework aluminophosphates, denoted AlPOs, has been prepared with neutral zeolitic frameworks and anionic frameworks showing wonderfully complex structural and compositional diversity. An insight into the construction of open-framework AlPOs revealing their general structural features and topological chemistry is provided in this tutorial review, and the role of templating and the designed construction and synthesis of AlPOs are discussed.

Zeolite-coated mesh film for efficient oil–water separation

Oil–water separations are helping with urgent issues due to increasing industrial oily wastewater, as well as frequent oil spill accidents. Membrane-based materials with special wettability are desired to separate oils from water. However, fabrication of energy-efficient and stable membranes that are suitable for practical oil–water separation remains challenging. Zeolite films have attracted intense research interest due to their unique pore character, excellent chemical, thermal and mechanical stability, etc. Here we first demonstrate zeolite-coated mesh films for gravity-driven oil–water separation. High separation efficiency of various oils can be achieved based on the excellent superhydrophilicity and underwater superoleophobicity of the zeolite surface. Flux and intrusion pressure are tunable by simply changing the pore size, dependent on the crystallization time of the zeolite crystals, of the zeolite meshes. More importantly, such films are corrosion-resistant in the presence of corrosive media, which gives them promise as candidates in practical applications of oil–water separation.

The Synthesis of an Extra-Large-Pore Zeolite with Double Three-Ring Building Units and a Low Framework Density†

Zeolites are crystalline inorganic solids formed by TO4 tetrahedra (T=Si, P, Al, Ge, etc.) with a well-defined system of regular pores having diameters up to about 2 nm. The possibility of tuning pore dimensions and framework compositions have made zeolites the most successful materials for applications in gas adsorption and separation and for catalysis. Their uses have been further expanded to microelectronics for preparing materials with low values of the high-frequency dielectric constant or manufacturing encapsulated light-emitting devices (LEDs), to medicine for diagnostic treatments and controlled drug delivery, or for release of semiotics for controlling insect populations in agricultural uses. Those applications often require structures with low framework densities, large internal volumes, and preferentially, extra-large pores. However, up to now, the number of known zeolites with a low framework density (FD 12) is almost negligible, and the number with extra-large pores ( 18-R) is also extremely small. Computational methods can predict a large number of thermodynamically feasible new structures, and they can stimulate and inspire the discovery of new structures. For example, Foster and Treacy have used a symmetry-constrained intersite bond searching method and have generated more than two million structures. With that methodology, the authors predicted a series of thermodynamically feasible extra-large-pore zeolites. Deem et al. have also modeled relatively large number of low density zeolites and were able to show that the low-energy and low-density materials also tend to have desirably large rings. Among the zeolite structures with extra large pores predicted by Foster and Treacy, there is one with 18 10 10-R pore topology that could be of particular interest for catalysis, as it combines an extra-large pore (18-R) for molecular accessibility with connected 10-R pores that can introduce shape-selectivity effects. Recently, the predicted zeolite was synthesized and named ITQ-33. This zeolite has 3-R and D4R units in the structure, and was at the time the silicate-based zeolite with the lowest framework density (12.3.T/1000 ). The pore topology of this extra-large-pore zeolite presented quite unique and interesting catalytic properties: The pore accessibility to large molecules through the 18-R was combined with shape selectivity in the 10-R pores for the primary products formed. In the same data base, Foster and Treacy also predicted an extra-large-pore zeolite that was closely related to ITQ-33 (Zeolite reference 191_4_1985). In that new structure, the 10-R pores of ITQ-33 were expanded to 12-R pores connecting the larger perpendicular 18-R channels. The result was a zeolite with 18 12 12 pore topology instead of the 18 10 10 for ITQ-33. In particular, along with D4R units, the new zeolite contains D3R units that have never been seen in synthesized zeolites, which could be related to geometric strains introduced in the framework owing to the formation of D3R based on silicon. In any case, the pore expansion with the 18 12 12-R pore system in the new zeolite should result in a decrease of the framework density from 12.3 in the case of ITQ-33 to 10.9 T atoms/1000 . Herein, we show that the zeolite containing D3R that was predicted above can be successfully synthesized (ITQ-44) as a silicogermanate by combining a relatively inexpensive, rigid and bulky organic structure-directing agent (SDA) with the directing effect of germanium. Furthermore, we show that in ITQ-44, germanium locates preferentially in D3R (with 50% Ge occupancy), followed by D4R (with 37% Ge occupancy). ITQ-44 was synthesized using (2’-(R),6’-(S))-2’,6’-dimethylspiro[isoindole-2,1’-piperidin-1’-ium] as the SDA (Supporting Information, Figure S1). The synthesis of ITQ-44 was carried out in fluoride media using high-throughput (HT) synthesis techniques, which involve the use of a 15-well multiautoclave. The XRD pattern of a calcined ITQ-44 sample (Figure 1) was collected (as described in the Supporting Information), and the crystal structure was solved using the program FOCUS. The agreement between the observed and calculated XRD patterns are shown in Figure 1; it certainly confirms that this structure corresponds to that of the pure silica polymorph of this material predicted by Foster and Treacy (reference number 191_4_19854). The structure of ITQ-44 is closely related to the previously described zeolite ITQ-33 (Figure 2). It also comprises a building unit formed by a [346] cage with two additional [*] J. Jiang, Dr. J. L. Jorda, Dr. M. J. Diaz-Cabanas, Prof. A. Corma Instituto de Tecnologia Quimica (UPV-CSIC) Universidad Politecnica de Valencia Consejo Superior de Investigaciones Cientificas Av. de los Naranjos s/n, 46022 Valencia (Spain) Fax: (+34)96-387-7809 E-mail: acorma@itq.upv.es

Near-infrared light-responsive supramolecular nanovalve based on mesoporous silica-coated gold nanorods

We constructed a novel cancer theranostic hybrid platform, based on mesoporous silica-coated gold nanorods (AuNR@MSN) gated by sulfonatocalix[4]arene (SC[4]A) switches, for bio-friendly near-infrared (NIR) light-triggered cargo release in a remote and stepwise fashion. The advantages of supramolecular switches, mesoporous silicas, and AuNRs were combined in one drug delivery system. Mesoporous silicas coated on AuNRs guarantee a high drug payload and can be easily post-functionalized. Significantly, the plasmonic heating from the NIR light-stimulated AuNR cores can decrease the ring-stalk binding affinity, leading to the dissociation of SC[4]A rings from the stalks, thus opening the nanovalves and releasing the cargos. The NIR light-responsive mechanized AuNR@MSN offers exciting prospects for non-invasive controlled drug delivery, being more effective and safer than other techniques.

Solvatochromic AIE luminogens as supersensitive water detectors in organic solvents and highly efficient cyanide chemosensors in water

A novel class of tetraphenylethene (TPE) derivatives TPEM and TPEBM containing dicyanovinyl groups were synthesized, possessing remarkable dual properties of solvatochromism and aggregation-induced emission (AIE). The combination of the electron-donating TPE and the electron-accepting dicyanovinyl group endow both compounds with a prominent solvatochromic effect, with emissions strongly dependent on solvent polarity and tunable from blue to red by changing the solvent from apolar to polar. They are found to be useful as fluorescent indicators for the qualitative and quantitative detection of low-level water content in organic solvents, and the detection limit can be as low as 63 ppm and 109 ppm in THF, respectively. Meanwhile, TPEM and TPEBM demonstrate typical AIE features and emit green-yellow and orange light in their aggregated states, respectively. Based on the AIE feature of TPE and the nucleophilic addition of cyanide, both compounds can act as colorimetric and fluorescent sensors for highly sensitive and selective detection of CN− in aqueous media under the assistance of cetyltrimethylammonium bromide (CTAB). The low detection limit of 0.2 μM as well as a short sensing process of only 100 seconds promise their practical application for detecting cyanide in drinking water. Furthermore, the development of easy-to-prepare test papers provides a convenient and reliable approach to monitor CN− in daily applications without resorting to instrumental analysis.

In Situ Confinement of Ultrasmall Pd Clusters within Nanosized Silicalite-1 Zeolite for Highly Efficient Catalysis of Hydrogen Generation

Well-dispersed and ultrasmall Pd clusters in nanosized silicalite-1 (MFI) zeolite have been prepared under direct hydrothermal conditions using [Pd(NH2CH2CH2NH2)2]Cl2 as precursor. High-resolution scanning transmission electron microscopy studies indicate that the Pd clusters are encapsulated within the intersectional channels of MFI, and the Pd clusters in adjacent channels visually aggregate, forming nanoparticles (NPs) of ∼1.8 nm. The resultant catalysts show an excellent activity and highly efficient H2 generation toward the complete decomposition of formic acid (FA) under mild conditions. Notably, thanks to the further reduced Pd NP size (∼1.5 nm) and the additionally introduced basic sites, the Pd/S-1-in-K catalyst affords turnover frequency values up to 856 h(-1) at 25 °C and 3027 h(-1) at 50 °C. The easy in situ confinement synthesis of metal clusters in zeolites endows the catalysts with superior catalytic activities, excellent recyclability, and high thermal stability, thus opening new perspectives for the practical application of FA as a viable and effective H2 storage material for use in fuel cells.

Accelerated crystallization of zeolites via hydroxyl free radicals

Radically faster synthesis Zeolite synthesis normally proceeds under basic conditions that allow the oxide bridges between aluminum and silicon atoms to break and reform. Feng et al. show that the formation of hydroxyl radicals, either by irradiation with ultraviolet light or with the Fenton reagent, can speed up the formation of the crystallized zeolite by about a factor of 2. Science, this issue p. 1188 Hydroxyl radicals generated with ultraviolet light or Fenton reagents can approximately double the rate of zeolite synthesis. In the hydrothermal crystallization of zeolites from basic media, hydroxide ions (OH–) catalyze the depolymerization of the aluminosilicate gel by breaking the Si,Al–O–Si,Al bonds and catalyze the polymerization of the aluminosilicate anions around the hydrated cation species by remaking the Si,Al–O–Si,Al bonds. We report that hydroxyl free radicals (•OH) are involved in the zeolite crystallization under hydrothermal conditions. The crystallization processes of zeolites—such as Na–A, Na–X, NaZ–21, and silicalite-1—can be accelerated with hydroxyl free radicals generated by ultraviolet irradiation or Fenton’s reagent.