Name: preparation of polyoxometalate-based photo-responsive membranes for the photo-activation of manganese oxide catalysts
Uploaded: 2018-08-07T14:30:00
Description: Watch this Scientific Journal Video about Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts at JoVE.com

A. Y. received financial support from the Global Center of Excellence for Mechanical Systems Innovation program of the University of Tokyo and from the University Tokyo Grant for Ph.D. Research. This work is partly supported by JSPS KAKENHI Grant-in-Aid for Young Scientists (B) (17K17718).

It is advisable to refer to all relevant material safety data sheets (MSDS) prior to using chemicals, as some used in these syntheses are highly acidic and corrosive. In addition, one polymer used in this work (polyacrylamide) may contain the carcinogenic monomer, acrylamide. The use of personal protective equipment (safety glasses, gloves, lab coat, full-length pants, closed-toe shoes) is required to prevent injuries from chemicals or heat. After conducting the cross-linking process, membrane samples should be stored in...

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A., Frei, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+Induced+Carbon+Dioxide+Reduction+by+Water+at+Binuclear+ZrOCoII+Unit+Coupled+to+Ir+Oxide+Nanocluster+Catalyst.">Light Induced Carbon Dioxide Reduction by Water at Binuclear ZrOCoII Unit Coupled to Ir Oxide Nanocluster Catalyst.</a> Journal of the American Chemical Society. 136, 11034-11042 (2014).</li><li>Kim, W., Frei, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Directed+Assembly+of+Cuprous+Oxide+Nanocatalyst+for+CO2+Reduction+Coupled+to+Heterobinuclear+ZrOCoII+Light+Absorber+in+Mesoporous+Silica.">Directed Assembly of Cuprous Oxide Nanocatalyst for CO2 Reduction Coupled to Heterobinuclear ZrOCoII Light Absorber in Mesoporous Silica.</a> ACS Catalysis. 5, 5627-5635 (2015).</li><li>Takashima, T., Nakamura, R., Hashimoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visible+Light+Sensitive+Metal+Oxide+Nanocluster+Photocatalysts:+Photo-Induced+Charge+Transfer+from+Ce(III)+to+Keggin-Type+Polyoxotungstates.">Visible Light Sensitive Metal Oxide Nanocluster Photocatalysts: Photo-Induced Charge Transfer from Ce(III) to Keggin-Type Polyoxotungstates.</a> The Journal of Physical Chemistry C. 113, 17247-17253 (2009).</li><li>Takashima, T., Yamaguchi, A., Hashimoto, K., Nakamura, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multielectron-transfer+Reactions+at+Single+Cu(II)+Centers+Embedded+in+Polyoxotungstates+Driven+by+Photo-induced+Metal-to-metal+charge+Transfer+from+Anchored+Ce(III)+to+Framework+W(VI).">Multielectron-transfer Reactions at Single Cu(II) Centers Embedded in Polyoxotungstates Driven by Photo-induced Metal-to-metal charge Transfer from Anchored Ce(III) to Framework W(VI).</a> Chemical Communications. 48, 2964-2966 (2012).</li><li>Takashima, T., Nakamura, R., Hashimoto, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Visible-Light-Absorbing+Lindqvist-Type+Polyoxometalates+as+Building+Blocks+for+All-Inorganic+Photosynthetic+Assemblies.">Visible-Light-Absorbing Lindqvist-Type Polyoxometalates as Building Blocks for All-Inorganic Photosynthetic Assemblies.</a> Electrochemistry. 79, 783-786 (2011).</li><li>Yamaguchi, A., Takashima, T., Hashimoto, K., Nakamura, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Design+of+Metal-to-metal+Charge-transfer+Chromophores+for+Visible-light+Activation+of+Oxygen-Evolving+Mn+Oxide+Catalysts+in+a+Polymer+Film.">Design of Metal-to-metal Charge-transfer Chromophores for Visible-light Activation of Oxygen-Evolving Mn Oxide Catalysts in a Polymer Film.</a> Chemistry of Materials. 29, 7234-7242 (2017).</li><li>Helen, M., Viswanathan, B., Murthy, S. 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J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Density+Functional+Study+of+the+Vibrational+Frequencies+of+&#945;-Keggin+Heteropolyanions.">Density Functional Study of the Vibrational Frequencies of &#945;-Keggin Heteropolyanions.</a> Chemical Physics. 287, 55-69 (2003).</li><li>Meng, Y., Song, W., Huang, H., Ren, Z., Chen, S. -. Y., Suib, S. 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It is critical to apply the cross-linking method introduced by Helen et al.14 to develop a self-standing membrane. When polyvinyl acetate was applied as the base polymer in this study, aggregation of H3PW12O40 occurred, which prevented formation of the self-standing membrane. However, when fabrication of the membrane was attempted utilizing Nafion as the base polymer, there was no progression of the reaction with Ce3+ and Co2+, althou...

The development of solar energy conversion systems using artificial photosynthesis or solar cells is necessary to enable the provision of alternative energy sources that can ameliorate global climate and energy issues1,2,3,4. Photo-functional materials can be broadly categorized into two groups, semiconductor-based systems and organic molecule-based systems. Although many different system types have been developed, improvements still need to be made because semiconductor systems suffer from a lack of precise charge transfer control, and organic molecule systems are not adequately durable with respect to photo-irradiation. However, the use of inorganic molecules as charge transfer unit components can improve these respective issues. For example, Frei et al. developed oxo-bridged metal systems grafted on the surface of mesoporous silica which can induce the metal-to-metal charge transfer (MMCT) by photo-irradiation and trigger photochemical redox reactions5,6,7,8,9.
Our group extended the single atomic system to a polynuclear system utilizing polyoxometalate (POM) as the electron acceptor10,11,12, with the expectation that use of the polynuclear system would be advantageous in the induction and control of the multi-electron transfer reaction, which is an important concept in energy conversion. In the protocol described here, we present the detailed method used to prepare the POM-based MMCT system, which works in a polymer matrix as we recently reported13. The membrane-type configuration is favorable for product separation between anodic and cathodic reaction products. The cross-linking method was applied, which enabled formation of a self-standing membrane, even with high POM contents. Photoelectrochemical measurements proved that appropriate selection of the donor metal is key to triggering the target. The POM/donor metal system works as a photo-sensitizer to activate multi-electron transfer catalysts under visible light irradiation. Although this work utilizes MnOx as a multi-electron transfer catalyst for the water oxidation reaction, this photo-functional system is also applicable for use with other types of reactions by utilizing various POMs, donor metals, and catalysts.

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			<td height="42" style="height:42px;width:287px;">Poly(vinyl Alcohol) 1000, Completely Hydrolyzed</td>
			<td style="width:119px;">Wako</td>
			<td style="width:119px;">162-16325</td>
			<td style="width:295px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:287px;">Polyacrylamide, Mv 6,000,000</td>
			<td style="width:119px;">Polyaciences, Inc.</td>
			<td style="width:119px;">2806</td>
			<td>May contain carcinogenic monomer, acrylamide.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">12 Tungsto(VI)phosphoric Acid n-Hydrate</td>
			<td style="width:119px;">Wako</td>
			<td style="width:119px;">164-02431</td>
			<td>Highly acidic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Acetone 99.5 + %(GC)</td>
			<td style="width:119px;">Wako</td>
			<td style="width:119px;">012-00343</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">25% Glutaraldehyde Solution</td>
			<td style="width:119px;">Wako</td>
			<td style="width:119px;">079-00533</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Hydrochloric Acid 35-37%</td>
			<td style="width:119px;">Wako</td>
			<td style="width:119px;">080-01066</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Cerium(III) Nitrate Hexahydrate 98 + %(Ti)</td>
			<td style="width:119px;">Wako</td>
			<td style="width:119px;">031-09732</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Cobalt(II) Chloride Hexahydrate 99 + %(Ti)</td>
			<td style="width:119px;">Wako</td>
			<td style="width:119px;">036-03682</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Pottasium Permanganate 99.3 + %(Ti)</td>
			<td style="width:119px;">Wako</td>
			<td style="width:119px;">167-04182</td>
			<td>Highly oxydative</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:287px;">Sodium Thiosulfate Pentahydrate 99 + %(Ti)</td>
			<td style="width:119px;">Wako</td>
			<td style="width:119px;">197-03585</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:287px;">Automatic spray gun</td>
			<td style="width:119px;">Lumina</td>
			<td style="width:119px;">ST-6</td>
			<td></td>
		</tr>
	</tbody>
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preparation of polyoxometalate-based photo-responsive membranes for the photo-activation of manganese oxide catalysts

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic polymers, with the aim of photo-activating oxygen-evolving manganese oxide catalysts, which are important components in artificial photosynthesis. The cross-linking technique was applied to obtain a self-standing membrane with a high PW12O403- content. Incorporation and structure retention of PW12O403- within the polymer matrix were confirmed by FT-IR and micro-Raman spectroscopy, and optical characteristics were investigated by UV-Vis spectroscopy, which revealed successful construction of the metal-to-metal charge transfer (MMCT) unit. After deposition of MnOx oxygen evolving catalysts, photocurrent measurements under visible light irradiation verified the sequential charge transfer, Mn &#8594; MMCT unit &#8594; electrode, and&#160;the photocurrent intensity was consistent with the redox potential of the donor metal (Ce or Co). This method provides a new strategy for preparing integrated systems involving catalysts and photon-absorption parts for use with photo-functional materials.

Retention of the POM structure in the polymer matrix was confirmed by FT-IR and micro-Raman spectroscopy (Figure 1); vibration peaks corresponding to the Keggin structure of POM were observed, and peaks of the polymers were found to be shifted due to hydrogen bonding with POM. Spectroscopic analysis was very useful for determining successful construction of the charge transfer unit, and this was also confirmed by the apparent color change of the samples (<str...

Watch this Scientific Journal Video about Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts at JoVE.com

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts

Here, we present a protocol to prepare charge transfer chromophores based on a polyoxometalate/polymer composite membrane.

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic ...

This method can help answer key questions in the solar-to-chemical energy conversion field such as artificial photosynthesis. The main advantage of this technique is that we can fabricate flexible, durable, and redox tunable photo-functional materials. First add two milliliters of polyvinyl alcohol solution and two milliliters of polyacrylamide solution to a 50 milliliter vial.Then add a triangular shaped stir bar and one gram of phosphotungstic acid to the vial. This cross-linking method was reported by another group and we modified the polyoxotungstate and its amount. Utilizing this method we can fabricate a membrane with an acid-type polyoxometalate instead of a salt-type.This is a key species to construct a photoresponsive membrane. Heat the vial to 70 degrees Celsius in a water bath under vigorous stirring and continue to stir for six hours after leaching at 70 degrees Celsius. Place a glass substrate on a hot plate pre-heated to 100 degrees Celsius and drop 750 microliters of the solution on to the substrate.To dry the sample store it in the dark overnight at room temperature. To prepare the crosslinking reagent add 72 milliliters of distilled water, 24 milliliters of acetone, 2 milliliters of 25%glyceraldehyde solution, and 2 milliliters of hydrochloric acid to a 100 milliliter vial. Place the glass substrate with the sample in a 9.5 centimeter Petri dish and add the crosslinking reagent until the membrane is completely immersed.After 30 minutes replace the crosslinking reagent with distilled water and wash once. If necessary peel the membrane from the glass substrate using a spatula and store it in distilled water in the dark. Add 2.08 grams of cerium nitrate hexahydrate and a stir bar to a 50 milliliter vial.Then add 30 milliliters of water to the vial and stir to dissolve the solid. Next place the membrane in a 9.5 centimeter Petri dish and add the cerium nitrate solution until the membrane is completely immersed. Place the Petri dish into a pre heated oven at 80 degrees Celsius for five hours.After cooling to room temperature replace the cerium nitrate solution with distilled water and wash once. Store the membrane and distilled water in the dark. To prepare a membrane with cobalt as the donor metal use the same preparation and reaction procedures as previously described except using 1.14 grams of cobalt chloride hexahydrate.Place the membranes onto a hot plate at 60 degrees Celsius with masks made of silicone rubber to determine the area to be used for deposition. Add 300 milliliters of a previously prepared colloidal manganese oxide solution to a 500 milliliter bottle connected to an automated spray gun above the hot plate and spray the solution onto the membranes. After manganese oxide deposition store the samples and distilled water in the dark.Retention of the POM structure in the polymer matrix was confirmed by micro-Raman and FT-IR spectroscopy. Vibration peaks corresponding to the Keggin structure of POM were observed and peaks of the polymers were found to be shifted due to hydrogen bonding with POM. Spectroscopic analysis was very useful for determining successful construction of the charge transfer unit and this was also confirmed by the apparent color change of the samples.In addition it was confirmed by UV-Vis spectroscopy and photo electro chemical measurements because charge transfer is achieved when all components are adequately aligned. In particular the spectroscopic and photoelectrochemical results confirmed one directional charge transfer under light irradiation which thus supports the validity of our synthetic method. The production of oxygen on manganese oxide was monitored using an indirect electrochemical method employing a rotating disk-ring electrode system where the reduction current corresponding to oxygen reduction could be observed under light irradiation.After its development this technique paves the way for researchers in the field of photochemistry to fabricate a redox-tunable and stable photosystem to trigger many photochemical reactions.

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Chemistry

Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material.

Various procedures are outlined to prepare atomically defined templates for epitaxial growth of complex oxide thin films. Chemical treatments of single crystalline SrTiO3 (001) and DyScO3 (110) substrates were performed to obtain atomically smooth, single terminated surfaces. Ca2 Nb3 O10- nanosheets were used to create atomically defined templates on arbitrary substrates.

Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain ...

Photochemical Oxidative Growth of Iridium Oxide Nanoparticles on CdSe@CdS Nanorods

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide (CdSe@CdS) nanorod photocatalysts. Seeded rods are grown using a colloidal hot-injection method and then moved to an aqueous medium by ligand exchange. CdSe@CdS nanorods, an iridium precursor and other salts are mixed and illuminated. The deposition process is initiated by absorption of photons by the semiconductor particle, which results with formation of charge carriers that are used to promote redox reactions. To insure photochemical oxidative growth we used an electron scavenger. The photogenerated holes oxidize the iridium precursor, apparently in a mediated oxidative pathway. This results in the growth of high quality crystalline iridium oxide particles, ranging from 0.5 nm to about 3 nm, along the surface of the rod. Iridium oxide grown on CdSe@CdS heterostructures was studied by a variety of characterization methods, in order to evaluate its characteristics and quality. We explored means for control over particle size, crystallinity, deposition location on the CdS rod, and composition. Illumination time and excitation wavelength were found to be key parameters for such control. The influence of different growth conditions and the characterization of these heterostructures are described alongside a detailed description of their synthesis. Of significance is the fact that the addition of iridium oxide afforded the rods astounding photochemical stability under prolonged illumination in pure water (alleviating the requirement for hole scavengers).

A protocol for the photochemical oxidative growth of small crystalline iridium oxide nanoparticles on the surface of CdSe@CdS seeded rod nanoparticles is presented.

We demonstrate a procedure for the photochemical oxidative growth of iridium oxide catalysts on the surface of seeded cadmium selenide-cadmium sulfide ...

Temperature-programmed Deoxygenation of Acetic Acid on Molybdenum Carbide Catalysts

Temperature programmed reaction (TPRxn) is a simple yet powerful tool for screening solid catalyst performance at a variety of conditions. A TPRxn system includes a reactor, furnace, gas and vapor sources, flow control, instrumentation to quantify reaction products (e.g., gas chromatograph), and instrumentation to monitor the reaction in real time (e.g., mass spectrometer). Here, we apply the TPRxn methodology to study molybdenum carbide catalysts for the deoxygenation of acetic acid, an important reaction among many in the upgrading/stabilization of biomass pyrolysis vapors. TPRxn is used to evaluate catalyst activity and selectivity and to test hypothetical reaction pathways (e.g., decarbonylation, ketonization, and hydrogenation). The results of the TPRxn study of acetic acid deoxygenation show that molybdenum carbide is an active catalyst for this reaction at temperatures above ca. 300 &#176;C and that the reaction favors deoxygenation (i.e., C-O bond-breaking) products at temperatures below ca. 400 &#176;C and decarbonylation (i.e., C-C bond-breaking) products at temperatures above ca. 400 &#176;C.

Presented here is a protocol for the operation of a micro-scale temperature-programmed reactor for evaluating the catalytic performance of molybdenum carbide during acetic acid deoxygenation.

Temperature programmed reaction (TPRxn) is a simple yet powerful tool for screening solid catalyst performance at a variety of conditions. A TPRxn system ...

Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are demonstrated here. The catalyst forms a substitutional solid solution structure, with a small and uniform particle size around 2 nm. This is realized by careful control over the impregnation, calcination, and reduction steps during catalyst preparation and is identified by advanced in situ synchrotron techniques. The catalyst propane dehydrogenation performance continuously improves with increasing Cu:Pt atomic ratio.

A convenient method for the synthesis of 2 nm supported bimetallic nanoparticle Pt-Cu catalysts for propane dehydrogenation is reported here. In situ synchrotron X-ray techniques allow for the determination of the catalyst structure, which is typically unobtainable using laboratory instruments.

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are ...

Aerosol-assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 &#176;C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 &#176;C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.

Columnar zinc oxide structures in the form of rods are synthesized via aerosol-assisted chemical vapor deposition without the use of pre-deposited catalyst-seed particles. This method is scalable and compatible with various substrates based on either silicon, quartz or polymers.

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, ...

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of NixNb1-xO nanoparticles with different atomic compositions (x = 0.03, 0.08, 0.15, and 0.20) have been prepared by chemical precipitation. These NixNb1-xO catalysts are characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The study revealed the sponge-like and fold-like appearance of Ni0.97Nb0.03O and Ni0.92Nb0.08O on the NiO surface, and the larger surface area of these NixNb1-xO catalysts, compared with the bulk NiO. Maximum surface area of 173 m2/g can be obtained for Ni0.92Nb0.08O catalysts. In addition, the catalytic hydroconversion of lignin-derived compounds using the synthesized Ni0.92Nb0.08O catalysts have been investigated.

Chemical Precipitation Method for the Synthesis of Nb2O5 Modified Bulk Nickel Catalysts with High Specific Surface Area

A protocol for the synthesis of sponge-like and fold-like Ni1-xNbxO nanoparticles by chemical precipitation is presented.

We demonstrate a method for the synthesis of NixNb1-xO catalysts with sponge-like and fold-like nanostructures. By varying the Nb:Ni ratio, a series of ...

Electrophoretic Crystallization of Ultrathin High-performance Metal-organic Framework Membranes

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and non-porous supports (polymer, ceramic, metal, carbon, and graphene). We developed a novel crystallization technique, which is termed the ENACT approach: the electrophoretic nuclei assembly for the crystallization of highly intergrown thin films (ENACT). This approach allows for a high density of heterogeneous nucleation of MOFs on a chosen substrate via the electrophoretic deposition (EPD) directly from the precursor sol. The growth of well-packed MOF nuclei leads to a highly intergrown polycrystalline MOF film. We show that this simple approach can be used for the synthesis of thin, intergrown zeolite imidazole framework (ZIF)-7 and ZIF-8 films. The resulting 500 nm-thick ZIF-8 membranes show a considerably high H2 permeance (8.3 x 10-6 mol m-2 s-1 Pa-1) and ideal gas selectivities (7.3 for H2/CO2, 15.5 for H2/N2, 16.2 for H2/CH4, and 2655 for H2/C3H8). An attractive performance for C3H6/C3H8 separation is also achieved (a C3H6 permeance of 9.9 x 10-8 mol m-2 s-1 Pa-1 and a C3H6/C3H8 ideal selectivity of 31.6 at 25 &#176;C). Overall, the ENACT process, owing to its simplicity, can be extended to synthesize intergrown thin films of a wide range of nanoporous crystalline materials.

A simple, reproducible, and versatile approach for the synthesis of intergrown, polycrystalline metal-organic framework membranes on a wide range of unmodified porous and non-porous supports is presented.

We report the synthesis of thin, highly intergrown, polycrystalline metal-organic framework (MOF) membranes on a wide range of unmodified porous and ...

Molten-Salt Synthesis of Complex Metal Oxide Nanoparticles

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. Here, we introduce the molten-salt synthesis (MSS) method for making metal oxide nanomaterials. Advantages over other methods include its simplicity, greenness, reliability, scalability, and generalizability. Using pyrochlore lanthanum hafnium oxide (La2Hf2O7) as a representative, we describe the MSS protocol for the successful synthesis of complex metal oxide nanoparticles (NPs). Furthermore, this method has the unique ability to produce NPs with different material features by changing various synthesis parameters such as pH, temperature, duration, and post-annealing. By fine-tuning these parameters, we are able to synthesize highly uniform, non-agglomerated, and highly crystalline NPs. As a specific example, we vary the particle size of the La2Hf2O7&#160;NPs by changing the concentration of the ammonium hydroxide solution used in the MSS process, which allows us to further explore the effect of particle size on various properties. It is expected that the MSS method will become a more popular synthesis method for nanomaterials and more widely employed in the nanoscience and nanotechnology community in the upcoming years.

Here, we demonstrate a unique, relatively low-temperature, molten-salt synthesis method for preparing uniform complex metal oxide lanthanum hafnate nanoparticles.

The development of feasible synthesis methods is critical for the successful exploration of novel properties and potential applications of nanomaterials. ...

Imine Metathesis by Silica-Supported Catalysts Using the Methodology of Surface Organometallic Chemistry

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared according to the methodology developed by surface organometallic chemistry (SOMC). In this framework, catalytic cycles can be determined by isolating crucial intermediates. All air-sensitive materials are handled under inert atmosphere (using gloveboxes or a Schlenk line) or high vacuum lines (HVLs, &#60;10-5 mbar). The preparation of SiO2-700 (silica dehydroxylated at 700 &#176;C) and subsequent applications (the grafting of complexes and catalytic runs) requires the use of HVLs and double-Schlenk techniques. Several well-known characterization methods are used, such as Fourier-transform infrared spectroscopy (FTIR), elemental microanalysis, solid-state nuclear magnetic resonance spectroscopy (SSNMR), and state-of-the-art dynamic nuclear polarization surface enhanced NMR spectroscopy (DNP-SENS). FTIR and elemental microanalysis permit scientists to establish the grafting and its stoichiometry. 1H and 13C SSNMR allows the structural determination of the hydrocarbon ligands coordination sphere. DNP SENS is an emerging powerful technique in solid characterization for the detection of poorly sensitive nuclei (15N, in our case). SiO2-700 is treated with about one equivalent of the metal precursor compared to the amount of surface silanol (0.30 mmol&#183;g-1) in pentane at room temperature. Then, volatiles are removed, and the powder samples are dried under dynamic high vacuum to afford the desired materials [(&#8801;Si-O-)Hf(&#951;2&#960;-MeNCH2)(&#951;1-NMe2)(&#951;1-HNMe2)]. After a thermal treatment under high vacuum, the grafted complex is converted into metal imido silica complex [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)]. [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] effectively promotes the metathesis of imines, using the combination of two imine substrates, N-(4-phenylbenzylidene)benzylamine, or N-(4-fluorobenzylidene)-4-fluoroaniline, with N-benzylidenetert-butylamine as substrates. A significantly lower conversion is observed with the blank runs; thus, the presence of the imido group in [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is correlated to the catalytic performance.

A new group IV metal catalyst for imine metathesis is prepared by grafting amine metal complex onto dehydroxylated silica. Surface metal fragments are characterized using FT-IR, elemental microanalysis, and solid-state NMR spectroscopy. Further dynamic nuclear polarization surface enhanced NMR spectroscopy experiments complement the determination of the coordination sphere.

With this protocol, a well-defined singlesite silica-supported heterogeneous catalyst [(&#8801;Si-O-)Hf(=NMe)(&#951;1-NMe2)] is designed and prepared ...

Tuning the Acidity of Pt/ CNTs Catalysts for Hydrodeoxygenation of Diphenyl Ether

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid nanosheets, a series of Pt/xHMNO6/CNTs with different solid acid compositions (x = 5, 20 wt%; M = Nb, Ta; N = Mo, W) have been prepared by carbon nanotube pretreatment, protonic exchange, solid acid exfoliation, aggregation and finally Pt particles impregnation. The Pt/xHMNO6/CNTs are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and NH3-temperature programmed desorption. The study revealed that HNbWO6 nanosheets were attached on CNTs, with some edges of the nanosheets being bent in shape. The acid strength of the supported Pt catalysts increases in the following order: Pt/CNTs &#60; Pt/5HNbWO6/CNTs &#60; Pt/20HNbMoO6/CNTs &#60; Pt/20HNbWO6/CNTs &#60; Pt/20HTaWO6/CNTs. In addition, the catalytic hydroconversion of lignin-derived model compound: diphenyl ether using the synthesized Pt/20HNbWO6 catalyst has been investigated.

A protocol for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs is presented.

We herein present a method for the synthesis of HNbWO6, HNbMoO6, HTaWO6 solid acid nanosheet modified Pt/CNTs. By varying the weight of various solid acid ...