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 water in dark conditions to avoid drying and the occurrence of any unnecessary photochemical reactions.
1. Preparation of POM/polymer Composite Membrane
Note: The synthesis procedure follows that reported in the article by Helen et al.14, except that the amount of POM was altered.
<ol>
	<li>Preparation of precursor polyvinyl alcohol (PVA) solution
	<ol>
		<li>Add 3 g of polyvinyl alcohol 1000 (completely hydrolyzed) and a stirring bar to a 50 mL vial.</li>
		<li>Add 27 mL of water to the vial.</li>
		<li>Heat the vial to 70 &#176;C within a water bath under stirring conditions to completely dissolve all polyvinyl alcohol particles.</li>
	</ol>
	</li>
	<li>Preparation of precursor polyacrylamide (PAM) solution
	<ol>
		<li>Add 0.75 g of polyacrylamide (see Table of Materials) and a stirring bar to a 50 mL vial.</li>
		<li>Add 29.25 mL of water to the vial.</li>
		<li>Heat the vial to 70 &#176;C within a water bath under stirring conditions to completely dissolve all polyacrylamide particles.</li>
	</ol>
	</li>
	<li>Preparation of mixture solution of POM and polymers
	<ol>
		<li>Add 2 mL of PVA solution and 2 mL of PAM solution to a 50 mL vial. 
		NOTE: As these polymer solutions have high viscocities, it is essential to accurately measure their volumes.</li>
		<li>Add a triangular-shaped stirring bar and 1 g of H3PW12O40 to the vial. 
		CAUTION: H3PW12O40 is a highly acidic material and should be stored in refrigerator. When working with it, use plastic materials and not metal ones.</li>
		<li>Heat the vial to 70 &#176;C within a water bath under vigorous stirring conditions and continue to stir for 6 h after leaching at 70 &#176;C.</li>
		<li>Place a glass substrate (5 x 5 cm2) on a hot plate (approximately 100 &#176;C) and drop 750 &#956;L of the solution onto the substrate. 
		NOTE: The solution should be kept hot during the dropping process to prevent the polymers from congealing.</li>
		<li>To dry the sample, keep it overnight in a dark condition at room temperature.</li>
	</ol>
	</li>
	<li>Cross-linking process for membrane sample
	<ol>
		<li>Add 72 mL of distilled water, 24 mL of acetone, 2 mL of 25% glutaraldehyde solution, and 2 mL of HCl to a 100 mL vial. This mixture is called the cross-linking reagent.</li>
		<li>Put the glass substrate with the sample in a Petri dish (approximately 9.5 cm diameter) and add the cross-linking reagent until the membrane is completely immersed.</li>
		<li>After 30 min, replace the cross-linking solution with distilled water, and wash once.</li>
		<li>Peel the membrane from the glass substrate using a spatula and store it in distilled water in dark conditions.This POM/polymer membrane is called POM/PVA/PAM. 
		NOTE: If the membrane is used for the next process (reaction with donor metals or MnOx deposition), the peeling-off process should be omitted.</li>
		<li>Use micro-Raman and FT-IR spectroscopy with POM/PVA/PAM to determine the chemical structure of the membrane13. Take an FT-IR spectrum of PVA/PAM (lacking POM) sample prepared by the same method as a reference.</li>
	</ol>
	</li>
</ol>
2. Reaction of POM/polymer Membrane with Donor Metals (Ce3+ and Co2+)
<ol>
	<li>Preparation of Ce3+ solution.
	<ol>
		<li>Add 2.08 g of Ce(NO3)3 &#8226; 6H2O and a stirring bar to a 50 mL vial.</li>
		<li>Add 30 mL of water to the vial and stir to dissolve all Ce(NO3)3.</li>
	</ol>
	</li>
	<li>Reaction of membrane sample with Ce3+
	<ol>
		<li>Put the membrane sample in a Petri dish (approximately 9.5 cm diameter) and add Ce3+ solution until the membrane is completely immersed.</li>
		<li>Put the Petri dish into a pre-heated oven at 80 &#176;C for 5 h.</li>
		<li>Replace the Ce3+ solution with distilled water and wash once.</li>
		<li>Store in distilled water in dark conditions.</li>
	</ol>
	</li>
	<li>Preparation of Co2+ solution
	<ol>
		<li>Use the same preparation and reaction procedures as with Ce3+, except using 1.14 g of CoCl2&#8226; 6H2O instead of Ce(NO3)3 &#8226; 6H2O. Samples reacted with Ce3+ and Co2+ are called POM/PVA/PAM/Ce and POM/PVA/PAM/Co, respectively.</li>
		<li>In this study, micro-Raman spectra of POM/PVA/PAM/Ce and POM/PVA/PAM/Co were examined to determine the molecular structure of PW12O403- after reaction with donor metal ions13. The optical properties of these samples were also examined using UV-Vis spectroscopy.</li>
	</ol>
	</li>
</ol>
3. Deposition of MnOx Water Oxidation Catalysts
NOTE: The preparation and deposition procedures of colloidal MnOx follow those in Perez-Benito et al. 198915 and Takashima et al. 201216, respectively.
<ol>
	<li>Preparation of colloidal MnOx solution
	<ol>
		<li>Add 39.4 mg of KMnO4 and a stirring bar to a 30 mL beaker. 
		NOTE: CAUTION: KMnO4 is a highly oxidative material; when working with it, use plastic spoons and not metal ones.</li>
		<li>Add 10 mL water to the beaker and stir to completely dissolve all KMnO4.</li>
		<li>Add 50 mg of Na2S2O3&#8226; 5H2O and an oval-shaped stirring bar to a 500 mL round-bottom flask.</li>
		<li>Add 20 mL water to the flask and stir to completely dissolve all Na2S2O3.</li>
		<li>Add 10 mL of KMnO4 solution to the flask drop-wise under vigorous stirring. 
		&#8203;Note: KMnO4 solution should be added slowly to prevent formation of aggregated MnO2.</li>
		<li>After adding the KMnO4 solution, immediately add 470 mL of distilled water to the flask.</li>
		<li>Keep stirring for over 2 h and then immediately use the solution for the next process (spraying).</li>
	</ol>
	</li>
	<li>Spraying MnOx colloidal solution onto membrane sample
	<ol>
		<li>Place the membrane samples onto a hot plate (approximately 60 &#176;C) with masks made of silicone rubber to determine the area to be used for deposition. 
		NOTE: For the deposition of MnOx catalysts, the membrane samples should be placed on glass substrates. If the membranes have not been peeled off from the substrate, put them onto a hot plate as they are. Keep the surface of the membrane wet during the deposition process. The mask also works as a weight to prevent the membranes from flying off due to the high air pressure from the spray gun.</li>
		<li>Add 300 mL of the colloidal MnOx solution to a 500 mL bottle connected to an automated spray gun (see Table of Materials) above the hot plate and spray the solution onto the membranes.</li>
		<li>When the volume in the bottle decreases, add the remaining colloidal solution to the bottle.</li>
		<li>Store the samples in distilled water in dark conditions. After MnOx-deposition, the samples are called POM/PVA/PAM/Ce/MnOx or POM/PVA/PAM/Co/MnOx.</li>
		<li>Electron transfer properties under visible-light irradiation of POM/PVA/PAM/Co/MnOx were monitored using photoelectrochemical measurements at a particular electrode potential. To conduct the photoelectrochemical experiment, the membrane sample was fabricated on transparent Sn-doped In2O3 (ITO) electrodes.</li>
	</ol>
	</li>
</ol>

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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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The authors have nothing to disclose.

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.

<table><tbody><tr><td>Poly(vinyl Alcohol) 1000, Completely Hydrolyzed</td><td>Wako</td><td>162-16325</td><td></td></tr><tr><td>Polyacrylamide, Mv 6,000,000</td><td>Polyaciences, Inc.</td><td>2806</td><td>May contain carcinogenic monomer, acrylamide.</td></tr><tr><td>12 Tungsto(VI)phosphoric Acid n-Hydrate</td><td>Wako</td><td>164-02431</td><td>Highly acidic</td></tr><tr><td>Acetone 99.5 + %(GC)</td><td>Wako</td><td>012-00343</td><td></td></tr><tr><td>25% Glutaraldehyde Solution</td><td>Wako</td><td>079-00533</td><td></td></tr><tr><td>Hydrochloric Acid 35-37%</td><td>Wako</td><td>080-01066</td><td></td></tr><tr><td>Cerium(III) Nitrate Hexahydrate 98 + %(Ti)</td><td>Wako</td><td>031-09732</td><td></td></tr><tr><td>Cobalt(II) Chloride Hexahydrate 99 + %(Ti)</td><td>Wako</td><td>036-03682</td><td></td></tr><tr><td>Pottasium Permanganate 99.3 + %(Ti)</td><td>Wako</td><td>167-04182</td><td>Highly oxydative</td></tr><tr><td>Sodium Thiosulfate Pentahydrate 99 + %(Ti)</td><td>Wako</td><td>197-03585</td><td></td></tr><tr><td>Automatic spray gun</td><td>Lumina</td><td>ST-6</td><td></td></tr></tbody></table>

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 ...

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7.6K Views.  The University of Tokyo. Hier presenteren we een protocol ter voorbereiding van de gratis overdracht chromophores gebaseerd op een polyoxometalate/polymeer samengestelde membraan.

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

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO2-Ag nanowires with a diameter of 200 nm and a length of 6-20 &#181;m were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO2-Ag nanowires, a TiO2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO2 gel resulted in the formation of crystalline TiO2 nanotubes. A subsequent Ag electrodeposition step inside the TiO2 nanotubes resulted in formation of coaxial TiO2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min&#160;of illumination, approximately 0.2 vol% H2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution.

Preparation and Use of Photocatalytically Active Segmented Ag|ZnO and Coaxial TiO2-Ag Nanowires Made by Templated Electrodeposition

Procedures are outlined to prepare segmented and coaxial nanowires via templated electrodeposition in nanopores. As examples, segmented nanowires consisting of Ag and ZnO segments, and coaxial nanowires consisting of a TiO2 shell and a Ag core were made. The nanowires were used in photocatalytic hydrogen formation experiments.

Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and ...

Engineering

Layer-by-layer Synthesis and Transfer of Freestanding Conjugated Microporous Polymer Nanomembranes

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in combination with their outstanding thermal and chemical stability, and low densities. However, their insoluble nature causes problems in their processing since usually applied techniques such as spin coating are not available. Especially for membrane applications, where the processing of CMP as thin films is desirable, the processing problems have hindered their commercial application.
Here we describe the interfacial synthesis of CMP thin films on functionalized substrates via molecular layer-by-layer (l-b-l) synthesis. This process allows the preparation of films with desired thickness and composition and even desired composition gradients.
The use of sacrificial supports allows the preparation of freestanding membranes by dissolution of the support after the synthesis. To handle such ultra-thin freestanding membranes the protection with sacrificial coatings showed great promise, to avoid rupture of the nanomembranes. To transfer the nanomembranes to the desired substrate, the coated membranes are upfloated at the air-liquid interface and then transferred via dip coating.

In this paper we describe the interfacial synthesis of conjugated microporous polymers (CMP) on sacrificial substrates, and the dissolution of the substrate for the preparation of freestanding CMP nanomembranes. In addition, we will describe how the fragile nanomembranes can be transferred to other substrates.

CMP as large surface area materials have attracted growing interest recently, due to their high variability in the incorporation of functional groups in ...

Improved Heterojunction Quality in Cu2O-based Solar Cells Through the Optimization of Atmospheric Pressure Spatial Atomic Layer Deposited Zn1-xMgxO

Atmospheric pressure spatial atomic layer deposition (AP-SALD) was used to deposit n-type ZnO and Zn1-xMgxO thin films onto p-type thermally oxidized Cu2O substrates outside vacuum at low temperature. The performance of photovoltaic devices featuring atmospherically fabricated ZnO/Cu2O heterojunction was dependent on the conditions of AP-SALD film deposition, namely, the substrate temperature and deposition time, as well as on the Cu2O substrate exposure to oxidizing agents prior to and during the ZnO deposition. Superficial Cu2O to CuO oxidation was identified as a limiting factor to heterojunction quality due to recombination at the ZnO/Cu2O interface. Optimization of AP-SALD conditions as well as keeping Cu2O away from air and moisture in order to minimize Cu2O surface oxidation led to improved device performance. A three-fold increase in the open-circuit voltage (up to 0.65 V) and a two-fold increase in the short-circuit current density produced solar cells with a record 2.2% power conversion efficiency (PCE). This PCE is the highest reported for a Zn1-xMgxO/Cu2O heterojunction formed outside vacuum, which highlights atmospheric pressure spatial ALD as a promising technique for inexpensive and scalable fabrication of Cu2O-based photovoltaics.

Improved Heterojunction Quality in Cu2O-based Solar Cells Through the Optimization of Atmospheric Pressure Spatial Atomic Layer Deposited Zn1-xMgxO

Here we present a protocol for synthesizing Zn1-xMgxO/Cu2O heterojunctions in open-air at low temperature via atmospheric pressure spatial atomic layer deposition (AP-SALD) of Zn1-xMgxO on cuprous oxide. Such high quality conformal metal oxides can be grown on a variety of substrates including plastics by this cheap and scalable method.

Atmospheric pressure spatial atomic layer deposition (AP-SALD) was used to deposit n-type ZnO and Zn1-xMgxO thin films onto p-type thermally oxidized Cu2O ...

Morphology Control for Fully Printable Organic&#8211;Inorganic Bulk-heterojunction Solar Cells Based on a Ti-alkoxide and Semiconducting Polymer

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting material. However, fullerene derivatives are air-sensitive; therefore, air-stable material is needed as an alternative. In the present study, we propose and describe the properties of Ti-alkoxide as an alternative electron-accepting material to fullerene derivatives to create highly air-stable BHJ solar cells. It is well-known that controlling the morphology in the photoactive layer, which is constructed with fullerene derivatives as the electron acceptor, is important for obtaining a high overall efficiency through the solvent method. The conventional solvent method is useful for high-solubility materials, such as fullerene derivatives. However, for Ti-alkoxides, the conventional solvent method is insufficient, because they only dissolve in specific solvents. Here, we demonstrate a new approach to morphology control that uses the molecular bulkiness of Ti-alkoxides without the conventional solvent method. That is, this method is one approach to obtain highly efficient, air-stable, organic-inorganic bulk-heterojunction solar cells.

A method for fully printable, fullerene-free, highly air-stable, bulk-heterojunction solar cells based on Ti alkoxides as the electron acceptor and the electron-donating polymer fabrication is described here. Moreover, a method for controlling the morphology of the photoactive layer through the molecular bulkiness of the Ti-alkoxide units is reported.

The photoactive layer of a typical organic thin-film bulk-heterojunction (BHJ) solar cell commonly uses fullerene derivatives as the electron-accepting ...

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, allowing for the synthesis of isotactic poly(&#945;-hydroxy acids) with expected molecular weights (&#62;140 kDa) and narrow molecular weight distributions (Mw/Mn &#60; 1.1). This ring-opening polymerization is mediated by Ni and Zn complexes in the presence of an alcohol initiator and a photoredox Ir catalyst, irradiated by a blue LED (400 - 500 nm). The polymerization is performed at a low temperature (-15 &#176;C) to avoid undesired side reactions. The complete monomer consumption can be achieved within 4 - 8 hours, providing a polymer close to the expected molecular weight with narrow molecular weight distribution. The resulted number-average molecular weight shows a linear correlation with the degree of polymerization up to 1000. The homodecoupling 1H NMR study confirms that the obtained polymer is isotactic without epimerization. This polymerization reported herein offers a strategy for achieving rapid, controlled O-carboxyanhydrides polymerization to prepare stereoregular poly(&#945;-hydroxy acids) and its copolymers bearing various functional side-chain groups.

Controlled Photoredox Ring-Opening Polymerization of O-Carboxyanhydrides Mediated by Ni/Zn Complexes

A protocol for the controlled photoredox ring-opening polymerization of O-carboxyanhydrides mediated by Ni/Zn complexes is presented.

Here, we describe an effective protocol that combines photoredox Ni/Ir catalysis with the use of a Zn-alkoxide for efficient ring-opening polymerization, ...

Surface Functionalization of Metal-Organic Frameworks for Improved Moisture Resistance

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. However, the main issue limiting their applicability is their poor stability in humid conditions. The common methods to overcome this problem involve the formation of strong metal-linker bonds by using highly charged metals, which is limited to a number of structures, the introduction of alkylic groups to the framework by post-synthetic modification (PSM) or chemical vapour deposition (CVD) to enhance overall hydrophobicity of the framework. These last two usually provoke a drastic reduction of the porosity of the material. These strategies do not permit to exploit the properties of the MOF already available and it is imperative to find new methods to enhance the stability of MOFs in water while keeping their properties intact. Herein, we report a novel method to enhance the water stability of MOF crystals featuring Cu2(O2C)4&#160;paddle-wheel units, such as HKUST (where HKUST stands for Hong Kong University of Science &#38; Technology), with the catechols functionalized with alkyl and fluoro-alkyl chains. By taking advantage of the unsaturated metal sites and the catalytic catecholase-like activity of CuII ions, we are able to create robust hydrophobic coatings through the oxidation and subsequent polymerization of the catechol units on the surface of the crystals under anaerobic and water-free conditions without disrupting the underlying structure of the framework. This approach not only affords the material with improved water stability but also provides control over the function of the protective coating, which enables the development of functional coatings for the adsorption and separations of volatile organic compounds. We are confident that this approach could also be extended to other unstable MOFs featuring open metal sites.

Robust functional catechol coatings were produced in one step by direct reaction of the material known as HKUST with synthetic catechols under anaerobic conditions. The formation of homogeneous coatings surrounding the entire crystal is ascribed to the biomimetic catalytic activity of Cu(II) dimers on the external surface of the crystals.

Metal-organic frameworks (MOFs) are a class of porous inorganic materials with promising properties in gas storage and separation, catalysis and sensing. ...

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 ...

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions

Developing photocatalytic H2 production devices is the one of the key steps for constructing a global H2-based renewable energy infrastructure. A number of photoactive assemblies have emerged where a photosensitizer and cobaloxime-based H2 production catalysts work in tandem to convert light energy into the H-H chemical bonds. However, the long-term instability of these assemblies and the need for hazardous proton sources have limited their usage. Here, in this work, we have integrated a stilbene-based organic dye into the periphery of a cobaloxime core via a distinct axial pyridine linkage. This strategy allowed us to develop a photosensitizer-catalyst hybrid structure with the same molecular framework. In this article, we have explained the detailed procedure of the synthesis of this hybrid molecule in addition to its comprehensive chemical characterization. The structural and optical studies have exhibited an intense electronic interaction between the cobaloxime core and the organic photosensitizer. The cobaloxime was active for H2 production even in the presence of water as the proton source. Here, we have developed a simple airtight system connected with an online H2 detector for the investigation of the photocatalytic activity by this hybrid complex. This photosensitizer-catalyst dyad present in the experimental setup continuously produced H2 once it was exposed in the natural sunlight. This photocatalytic H2 production by the hybrid complex was observed in aqueous/organic mixture media in the presence of a sacrificial electron donor under complete aerobic conditions. Thus, this photocatalysis measurement system along with the photosensitizer-catalyst dyad provide valuable insight for the development of next generation photocatalytic H2 production devices.

Developing Photosensitizer-Cobaloxime Hybrids for Solar-Driven H2 Production in Aqueous Aerobic Conditions

We have directly incorporated a stilbene-based organic dye into a cobaloxime core to generate a photosensitizer-catalyst dyad for photocatalytic H2 production. We have also developed a simple experimental setup for evaluating the light-driven H2 production by photocatalytic assemblies.

Developing photocatalytic H2 production devices is the one of the key steps for constructing a global H2-based renewable energy infrastructure. A number ...

Metal Oxide Heterojunction for Photocatalytic Activities

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale applications. Sol-gel-based solution combustion synthesis (SG-SCS) is a simple method to produce ordered porous materials. In this regard, Pearson&#39;s hard and soft acids and bases theory assists in selecting host-dopant reactivity to form a proper heterojunction.
The formation of a heterojunction also changes the essential properties of the materials, improving photocatalysis via charge transfer or synergistic activities. A calcination temperature of 500 &#176;C is ideal for this process based on the results of the stability assessment via a differential thermogravimetry ratio analysis (DTG).
The nanoscale dimensions of the nanoparticles (NPs) and nanocomposites (NCs) generated were validated using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Furthermore, the scanning electron microscopy micrographs and BET analyses confirmed the porosity nature of the materials. HRTEM, X-ray photoelectron spectroscopy, and energy-dispersive X-ray investigations established the materials composition. The study found that NCs degraded the acid orange 8 (AO8) color more efficiently than bare ZnO.

The development of a heterojunction boosts the photocatalytic activities of solution combustion synthesis, which is a time-/energy-efficient process. Advanced analytical characterization techniques were used in this protocol to evaluate the materials&#39; characteristics, and nanocomposites demonstrated improved acid orange-8 dye degradation.

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale ...

Hydrothermal Synthesis of Persistent Luminescent Nanoparticles

Synthesis of Persistent Luminescent Nanoparticles for Rewritable Displays and Illumination Applications

Persistent luminescent nanoparticles (PLNPs) possess the capabilities to maintain extended longevity and robust emission even after the excitation has ceased. PLNPs have been widely used across various domains, including information displays, data encryption, biological imaging, and artistic decoration with sustained and vivid luminosity, providing boundless possibilities for a variety of innovative technology and artistic projects. This protocol focuses on an experimental procedure for the hydrothermal synthesis of PLNPs. The successful synthesis of enduring luminescent nanomaterials with Mn2+ or Cr3+ serving as a luminescent center in Zn2GeO4: Mn (ZGO: Mn) or ZnGa2O4: Cr highlights the universality of this synthetic method. On the other hand, the optical properties of ZGO: Mn can be changed by adjusting the pH of precursor solutions, demonstrating the tunability of the protocol. When charged with ultraviolet (UV) at a wavelength of 365 nm for 3 min and then stopped, PLNPs exhibit the remarkable capacity to generate afterglow efficiently and consistently, which makes them ideal for making two-dimensional rewritable displays and three-dimensional transparent, luminous artworks. This protocol outlined in this paper provides a feasible method for the synthesis of persistent luminescent nanoparticles for further illumination and imaging applications, opening up novel prospects for the fields of science and art.

Author Spotlight: Advancing Bioimaging and Therapy with Functional Nanomaterials

A protocol is presented for the synthesis of persistent luminescent nanomaterials (PLNPs) and their potential applications in rewritable displays and artistic processing utilizing the afterglow effect under ultraviolet light (365 nm) irradiation.

Persistent luminescent nanoparticles (PLNPs) possess the capabilities to maintain extended longevity and robust emission even after the excitation has ...

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

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