The Authors are grateful for the financial support received from the European Commission under the CharM and AdvCharM of the Climate-KIC Programme and from the Spanish Ministry of Science, Innovation and Universities under RTC-2017-6087-5 of the &#x201C;Investigaci&#x00F3;n, Desarrollo e Innovacion Orientada a los Retos de la Sociedad&#x201D; Programme and under the Severo Ochoa program (SEV-2016-0683).

1. Hydrothermal carbonization of household leftovers
<ol>
	<li>Calculation of the suitable amounts of water and biomass for the reaction mixture.
	<ol>
		<li>The reaction mixture must fill half of the volume of the autoclave. Assume that the density of the mixture is approximately 1 g/mL and calculate the amounts by weight. Approximately 80 wt% should be water and the rest solid matter. Overall water content is not crucial and may range from 70 to 85 wt%.</li>
		<li>Select the biomass from kitchen leftovers such as fruit peels or inedible vegetable parts. With the aim to calculate an exact mass balance for section 1, dry a sample of the biomass at 100&#8211;105 &#176;C in an oven for 2 h or overnight. The obtained mass is the solid matter of the biomass. Alternatively, use literature data (accuracy is reduced).</li>
		<li>Calculate how much wet biomass is required to charge the autoclave with 20 wt% of solid matter and how much of water is to be introduced together with it. Calculate how much water is required to reach the desired water amount in the reactor.</li>
	</ol>
	</li>
	<li>Charging the autoclave. 
	CAUTION: The autoclave has to be provided with a rupture disc with a burst pressure of 50 bar.
	<ol>
		<li>Weigh biomass and water as calculated in step 1.1.3 and introduce both into the autoclave.</li>
		<li>Close the autoclave and pressurize it with nitrogen up to 20 bar. Confirm that there is no pressure loss over 30 min. This ensures that the vessel is properly closed without any leaks. Release the pressure and close the vessel again.</li>
	</ol>
	</li>
	<li>Carbonization reaction.
	<ol>
		<li>Switch on the stirring. Heat the autoclave to 215 &#176;C within 30 min and maintain the temperature for at least 4 h or overnight.</li>
		<li>Monitor the pressure for the first 2 h. In general, it follows the vapor pressure curve of water up to 21 bar. If the pressure does not increase, either the heating is not working correctly, or the vessel is not closed properly. If this happens, stop the reaction and check the heating and sealing.</li>
		<li>In rare cases, e.g., if the biomass is prone to decarboxylation, the maximum pressure might be 5 to 10 bar higher than the 21 bar caused by steam pressure at 215 &#176;C. If the pressure exceeds 35 bar, switch off the heating and interrupt the reaction. After it has cooled down to room temperature carefully release the remaining pressure and start again from step 1.3.1.</li>
	</ol>
	</li>
	<li>Recovery of the raw hydrochar.
	<ol>
		<li>When the autoclave has cooled down to room temperature by natural cooling, carefully release any residual pressure and open the autoclave.</li>
		<li>Separate solid and liquid by vacuum filtration with a Buchner funnel. Dispose the of the liquid phase as aqueous solution among hazardous laboratory waste.</li>
		<li>Dry the solid at 100 to 105 &#176;C in an oven for 2 h or overnight. Calculate the mass balance of the first step, i.e. the hydrothermal carbonization (section 1). For this, take into account dry weight of the biomass and dry weight of the product.</li>
	</ol>
	</li>
</ol>
2. Thermal treatment of raw hydrochar in batch mode
<ol>
	<li>Weigh 1 g of dry raw hydrochar and place it on a glass frit of a tubular quartz reactor (batch reactor).</li>
	<li>For larger amounts such as 10 to 20 g, use pelletized material with a particle size of 0.2 to 6 mm. Otherwise, the occurrence of preferred channels might impede homogeneous treatment of the sample.</li>
	<li>Place the heating mantle of the reactor and connect a down-flow nitrogen stream of 20 mL/min. Place a small beaker below the reactor outlet to collect condensed liquids. Cooling is not required.</li>
	<li>Aspirate gases at the outlet and conduct them to the exhaust or place the whole reactor in an exhaust hood. Heat the reactor to 275 &#176;C with a ramp of 10 degrees/min. Maintain the temperature for 1 h.</li>
	<li>When cooled down to room temperature again, disconnect the gas flow. Discard the liquid collected in the beaker to the nonhalogenated organic residues. Recover the carbon material and weigh it. Calculate the mass balance for section 2, i.e. the thermal treatment, from the masses employed and obtained, and for the overall reaction from the mass obtained in the thermal treatment and the dry biomass employed in the carbonization step.</li>
</ol>
3. Analysis of the final product by thermogravimetry (TG)
<ol>
	<li>Crush the product in a mortar and weigh a 10 mg sample in a crucible of the apparatus.</li>
	<li>Place the crucible in the autosampler of the TG apparatus and select the analysis conditions: adjust the maximum temperature to 600 &#176;C and the employ air as sweep gas and a temperature ramp of 10 degrees/min.</li>
	<li>Start the analysis.</li>
	<li>Quantify the mass loss at 275 &#176;C in the TG curve by calculating the difference between initial weight and that observed at this temperature (see Figure 2). Express the mass loss as percentage of the initial weight. Compare the values of treated and raw samples. A clear reduction is observed.</li>
</ol>

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Marisa Hernandez and Borja Oliver-Tomas are employees of Ingelia SL that produced hydrochar samples used in this article. Maria Consuelo Hern&#x00E1;ndez-Soto, Estefan&#x00ED;a Ponce, and Michael Renz have nothing to disclose.

The hydrothermal carbonization is a very resilient method and always provides a carbonaceous product, i.e., the hydrochar. However, yield and properties of the hydrochar might vary, not only due to reaction conditions or reaction control, but rather due to heterogeneity and variation of the biomass. For instance, mass yield and C content might be higher for lignocellulosic biomass with a higher lignin content or woody materials.
In the case that a higher carbonization degree (quantified by elemental analysis) is desired, the hydrochar can be resubmitted to the carbonization reaction. Alternatively, in future reactions reaction time can be prolonged or reaction temperature can be increased (caution, autogenous water pressure increases exponentially with temperature).
The outcome of the thermal treatment also depends on the composition of the raw material. For instance, if the biomass involves other organic components such as vegetable oil, the thermal treatment will separate these volatile compounds from the solid and mass loss will be greater.
In the present protocol, both steps are carried out in batch mode. For industrial application, the whole production process has to be carried out in continuous mode. The hydrothermal carbonization is already carried out as a continuous process26,27, but the thermal treatment still has to be developed further. The final aim is to convert the OFMSW into a carbonaceous material with peat properties so that employing peat (considered to be a fossil material) increases in agriculture and horticulture with clear benefits for the environment and as a contributor to climate change mitigation.

Hydrothermal carbonization (HTC) is an emerging technology for waste management of wet, lignocellulosic resources. This technology was rediscovered by Antonietti and Titirici and applied to pine needles, pine cones, oak leaves and orange peels1. Thereby, the biomass is converted into hydrochar, a carbonaceous solid similar to lignite2,3 or peat4,5. Since then, many residual feedstocks have have processed such as agro-industrial waste6,7,8, the organic fraction of municipal solid waste (OFMSW)9, or paper mill sludge10. The technology is also used as biomass pretreatment for pyrolysis and gasification11. In addition, the procedure provides modern nanotechnology materials from homogeneous renewable resources such as sugars or cellulose. These advanced materials have potential for future applications as electrodes for rechargeable batteries, fuel cells or supercapacitators, gas storage, sensors or drug delivery12,13.
Hydrochar is a carbon material and as such it could be used as renewable solid fuel, especially when produced from low-value, heterogeneous resources with variable (seasonal or regional) composition. However, hydrochar production and its application to soil, instead of its immediate combustion, will have a triple contribution to climate change mitigation. First, choosing HTC as waste management technology avoids emission of the powerful greenhouse gas methane during composting or uncontrolled decomposition14,15. Second, avoiding combustion of hydrochar after a short period of time and applying it to soil, removes the carbon dioxide from the atmosphere for a longer period of time, i.e., it consists in real carbon capture and storage (CCS)16,17. Third, in general, char amended soils are more fertile soils (black soils) and plant growth is increased.18,19 This reduces fertilizer use and carbon dioxide emissions related to their production, besides preserving resources. Moreover, additional plant growth removes more carbon dioxide from the atmosphere.
Although it is quite clear that there are many apparent arguments for the application of hydrochar to soil, the material involves an inconvenience: raw hydrochar does not behave exactly as biochar that is produced by pyrolysis. Hydrochar does not clearly increase plant growth or even worse, frequently it causes a rather negative effect20,21,22. Therefore, farmers are not encouraged to apply it, and even less to pay money for it. Fortunately, this drawback can be mitigated or eliminated. The easiest approach is to simply wait for the second cultivation cycle22. Also washings20,21,22,23 or co-composting24 are successful treatments for this purpose. However, all these procedures require time or produce an aqueous stream that need further care.
Recently, it has been shown that raw hydrochar can be subjected to a soft thermal post-treatment25. The aim of this procedure is to simply desorb the undesired volatile and harmful substances. The resulting concentrated flow of mainly organic matter can be valorized thermally in situ. As such, the energy balance of the HTC plant is improved and any environmental risk of the side stream is prevented. Germination tests show that the treatment is successful when carried out at temperatures of 275 &#176;C or higher.
The present protocol (see Figure 1) involves two reaction steps and one straightforward analytical method for the evaluation of the reaction outcome. During the first step, biomass is converted into raw hydrochar in an autoclave at 215 &#176;C and at 21-bar pressure. Here, household leftovers are employed as starting material. These include all kinds of vegetable material such as fruit peels, fruit stones, inedible vegetable parts, coffee grounds, kitchen paper, compostable plastic bags, etc. The carbonaceous material is collected by filtration and dried. For the second step, it is placed on a glass frit of a vertical tubular reactor applying gas flow in a downward flow direction. The tube is heated to 275 &#176;C for 1 h. The resulting solid is analyzed by thermogravimetry (TG) in air. The material loss up to 275 &#176;C is quantified and compared to the loss observed with untreated hydrochar. The carbon material can be further characterized by elemental analysis (C, H, N, and S), ash content and ash composition (mainly Ca, Al, Si, and P).

<table> 
<tbody>
<tr>
<td>Autoclave with a vessel volume of 100 to 500 mL</td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>Continuous flow tubular calcination reactor with glass frit</td>
<td></td>
<td></td>
<td>Cuartz tube: 37 cm long, 20 mm outer diameter, glass frit (3 mm thickness) at 22 cm from the top of the tube</td>
</tr>
<tr>
<td>Vacuum filtration system</td>
<td></td>
<td></td>
<td>Buchner funnel, filter paper, filter flask</td>
</tr>
<tr>
<td>Oven for drying samples at 100 &#x00B0;C</td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>Thermogravimetric analyzer</td>
<td></td>
<td></td>
<td>E.g. Netzsch STA 449F3 Jupiter with Netzsch STA 449F3 software and Netzsch ASC Manager software for autosampler control</td>
</tr>
<tr>
<td>Any king of vegetable biomass (for examples see tables 1 and 2) including:</td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>Compostable plastic bags from BASF</td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>Plastic bags for collection of the organic fraction in households, provided by local waste managers</td>
<td></td>
<td></td>
<td></td>
</tr>
<tr>
<td>Compostable coffee capsules ecovio (BASF)</td>
<td></td>
<td></td>
<td></td>
</tr>
</tbody>
</table>

transformation of organic household leftovers into a peat substitute

A two-step procedure is described for the synthesis of a carbon material with a similar composition and properties as peat. The produced hydrochar is made suitable for agricultural applications by removing plant growing inhibitory substances. Wet household waste such as fruit peel, coffee grounds, inedible vegetable parts, or wet lignocellulosic material in general, are treated in presence of water at 215 &#x00B0;C and 21 bar in an autoclave, i.e., by hydrothermal carbonization. All these leftovers have a considerable water content of up to 90 weight % (wt%). Adding water extends the procedure to drier materials such as nutshells or even garden prunings and compostable polymers, i.e., the plastic bag for collection of the leftovers.
Usually, the resulting carbon material, called hydrochar, produces a negative effect on plant growth when added to soil. It is supposed that this effect is caused by adsorbed phytotoxic compounds. A simple post-treatment under inert atmosphere (absence of oxygen) at 275 &#x00B0;C removes these substances. Therefore, the raw hydrochar is placed on a glass frit of a vertical tubular quartz reactor. A nitrogen gas flow is applied in down-flow direction. The tube is heated to the desired temperature by means of a heating mantle for up to one hour.
The success of the thermal treatment is easily quantified by thermogravimetry (TG), carried out in air. A weight loss is determined when the temperature of 275 &#x00B0;C is reached, since volatile content is desorbed. Its amount is reduced in the final material, in comparison to the untreated hydrochar.
The two-step treatment converts household leftovers, including compostable bags employed for their collection, into a carbon material that may serve as plant growth promoter and, at the same time, as a carbon sink for climate change mitigation.

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Transformation of Organic Household Leftovers into a Peat Substitute

A protocol for hydrothermal carbonization of vegetable food waste in an autoclave is presented, with subsequent dry thermal treatment at 275 &#x00B0;C in a continuous flow reactor desorbing volatile organic substances. The aim is to produce a carbon material suitable as soil amendment product or substrate component.

A two-step procedure is described for the synthesis of a carbon material with a similar composition and properties as peat. The produced hydrochar is made ...

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Chemistry

8.1K Views.  Universitat Politècnica de València-Consejo Superior de Investigaciones CientÍficas. A protocol for hydrothermal carbonization of vegetable food waste in an autoclave is presented, with subsequent dry thermal treatment at 275 °C in a continuous flow reactor desorbing volatile organic substances. The aim is to produce a carbon material suitable as soil amendment product or substrate component.

Video: Transformation of Organic Household Leftovers into a Peat Substitute

Preparation and Use of Samarium Diiodide (SmI2) in Organic Synthesis: The Mechanistic Role of HMPA and Ni(II) Salts in the Samarium Barbier Reaction

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of molecular iodine to samarium metal in THF.1,2-3 It is a mild and selective single electron reductant and its versatility is a result of its ability to initiate a wide range of reductions including C-C bond-forming and cascade or sequential reactions. SmI2 can reduce a variety of functional groups including sulfoxides and sulfones, phosphine oxides, epoxides, alkyl and aryl halides, carbonyls, and conjugated double bonds.2-12 One of the fascinating features of SmI-2-mediated reactions is the ability to manipulate the outcome of reactions through the selective use of cosolvents or additives. In most instances, additives are essential in controlling the rate of reduction and the chemo- or stereoselectivity of reactions.13-14 Additives commonly utilized to fine tune the reactivity of SmI2 can be classified into three major groups: (1) Lewis bases (HMPA, other electron-donor ligands, chelating ethers, etc.), (2) proton sources (alcohols, water etc.), and (3) inorganic additives (Ni(acac)2, FeCl3, etc).3
Understanding the mechanism of SmI2 reactions and the role of the additives enables utilization of the full potential of the reagent in organic synthesis. The Sm-Barbier reaction is chosen to illustrate the synthetic importance and mechanistic role of two common additives: HMPA and Ni(II) in this reaction. The Sm-Barbier reaction is similar to the traditional Grignard reaction with the only difference being that the alkyl halide, carbonyl, and Sm reductant are mixed simultaneously in one pot.1,15 Examples of Sm-mediated Barbier reactions with a range of coupling partners have been reported,1,3,7,10,12 and have been utilized in key steps of the synthesis of large natural products.16,17 Previous studies on the effect of additives on SmI2 reactions have shown that HMPA enhances the reduction potential of SmI2 by coordinating to the samarium metal center, producing a more powerful,13-14,18 sterically encumbered reductant19-21 and in some cases playing an integral role in post electron-transfer steps facilitating subsequent bond-forming events.22 In the Sm-Barbier reaction, HMPA has been shown to additionally activate the alkyl halide by forming a complex in a pre-equilibrium step.23
Ni(II) salts are a catalytic additive used frequently in Sm-mediated transformations.24-27 Though critical for success, the mechanistic role of Ni(II) was not known in these reactions. Recently it has been shown that SmI2 reduces Ni(II) to Ni(0), and the reaction is then carried out through organometallic Ni(0) chemistry.28
These mechanistic studies highlight that although the same Barbier product is obtained, the use of different additives in the SmI2 reaction drastically alters the mechanistic pathway of the reaction. The protocol for running these SmI2-initiated reactions is described.

Preparation and Use of Samarium Diiodide SmI2 in Organic Synthesis: The Mechanistic Role of HMPA and NiII Salts in the Samarium Barbier Reaction

A straightforward procedure for the preparation of samarium diiodide (SmI2) in THF is described. The role of two main additives namely hexamethylphosphoramide (HMPA) and Ni(acac)2 in Sm mediated reactions is demonstrated in the Sm-Barbier reaction.

Although initially considered an esoteric reagent, SmI2 has become a common tool for synthetic organic chemists. SmI2 is generated through the addition of ...

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. Specifically, the sapphire cell enables visual data collection from multiple loadings to solve a set of material balances to precisely determine phase composition. Ternary phase diagrams can then be established to determine the proportion of each component in each phase at a given condition. In principle, any ternary system can be studied although ternary systems (gas-liquid-liquid) are the specific examples discussed herein. For instance, the ternary THF-Water-CO2 system was studied at 25 and 40&#160;&#176;C and is described herein. Of key importance, this technique does not require sampling. Circumventing the possible disturbance of the system equilibrium upon sampling, inherent measurement errors, and technical difficulties of physically sampling under pressure is a significant benefit of this technique. Perhaps as important, the sapphire cell also enables the direct visual observation of the phase behavior. In fact, as the CO2 pressure is increased, the homogeneous THF-Water solution phase splits at about 2 MPa. With this technique, it was possible to easily and clearly observe the cloud point and determine the composition of the newly formed phases as a function of pressure.
The data acquired with the sapphire cell technique can be used for many applications. In our case, we measured swelling and composition for tunable solvents, like gas-expanded liquids, gas-expanded ionic liquids and Organic Aqueous Tunable Systems (OATS)1-4. For the latest system, OATS, the high-pressure sapphire cell enabled the study of (1) phase behavior as a function of pressure and temperature, (2) composition of each phase (gas-liquid-liquid) as a function of pressure and temperature and (3) catalyst partitioning in the two liquid phases as a function of pressure and composition. Finally, the sapphire cell is an especially effective tool to gather accurate and reproducible measurements in a timely fashion.

High-pressure Sapphire Cell for Phase Equilibria Measurements of CO2/Organic/Water Systems

The high pressure sapphire cell apparatus is a unique tool to study, without sampling, phase behavior under a wide range of pressures. Using a cathetometer, very precise volume measurements can be recorded to measure liquid expansion and phase composition. Thus, this synthetic method enables the study of (1) phase equilibria of multi-component mixtures and (2) the partition behavior of catalyst or model compounds as a function of pressure.

The high pressure sapphire cell apparatus was constructed to visually determine the composition of multiphase systems without physical sampling. ...

Analysis of Volatile and Oxidation Sensitive Compounds Using a Cold Inlet System and Electron Impact Mass Spectrometry

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The analysis of volatile and oxidation sensitive compounds by mass spectrometry is not easily achieved, as all state-of-the-art mass spectrometric methods require at least one sample preparation step, e.g., dissolution and dilution of the analyte (electrospray ionization), co-crystallization of the analyte with a matrix compound (matrix-assisted laser desorption/ionization), or transfer of the prepared samples into the ionization source of the mass spectrometer, to be conducted under atmospheric conditions. Here, the use of a sample inlet system is described which enables the analysis of volatile metal organyls, silanes, and phosphanes using a sector field mass spectrometer equipped with an electron impact ionization source. All sample preparation steps and the sample introduction into the ion source of the mass spectrometer take place either under air-free conditions or under vacuum, enabling the analysis of compounds highly susceptible to oxidation. The presented technique is especially of interest for inorganic chemists, working with metal organyls, silanes, or phosphanes, which have to be handled using inert conditions, such as the Schlenk technique. The principle of operation is presented in this video.

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The presented technique is especially of interest for inorganic chemists, working with metal organyls, silanes, or phosphanes which have to be handled using inert conditions, such as the Schlenk technique.

This video presents a protocol for the mass spectrometrical analysis of volatile and oxidation sensitive compounds using electron impact ionization. The ...

Synthesis and Characterization of Functionalized Metal-organic Frameworks

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and technological applications. Their signature property is their ultrahigh porosity, which however imparts a series of challenges when it comes to both constructing them and working with them. Securing desired MOF chemical and physical functionality by linker/node assembly into a highly porous framework of choice can pose difficulties, as less porous and more thermodynamically stable congeners (e.g., other crystalline polymorphs, catenated analogues) are often preferentially obtained by conventional synthesis methods. Once the desired product is obtained, its characterization often requires specialized techniques that address complications potentially arising from, for example, guest-molecule loss or preferential orientation of microcrystallites. Finally, accessing the large voids inside the MOFs for use in applications that involve gases can be problematic, as frameworks may be subject to collapse during removal of solvent molecules (remnants of solvothermal synthesis). In this paper, we describe synthesis and characterization methods routinely utilized in our lab either to solve or circumvent these issues. The methods include solvent-assisted linker exchange, powder X-ray diffraction in capillaries, and materials activation (cavity evacuation) by supercritical CO2 drying. Finally, we provide a protocol for determining a suitable pressure region for applying the Brunauer-Emmett-Teller analysis to nitrogen isotherms, so as to estimate surface area of MOFs with good accuracy.

Synthesis, activation, and characterization of intentionally designed metal-organic framework materials is challenging, especially when building blocks are incompatible or unwanted polymorphs are thermodynamically favored over desired forms. We describe how applications of solvent-assisted linker exchange, powder X-ray diffraction in capillaries and activation via supercritical CO2 drying, can address some of these challenges.

Metal-organic frameworks have attracted extraordinary amounts of research attention, as they are attractive candidates for numerous industrial and ...

Synthesis of a Water-soluble Metal&#8211;Organic Complex Array

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as Ru(II), Pt(II), and Rh(III). The compound, named as a water-soluble metal-organic complex array (WSMOCA), is obtained through 1) the conventional solution-chemistry-based preparation of the corresponding metal complex monomers having a 9-fluorenylmethyloxycarbonyl (Fmoc)-protected amino acid moiety and 2) their sequential coupling together with other water-soluble organic building units on the surface-functionalized polymeric resin by following the procedures originally developed for the solid-phase synthesis of polypeptides, with proper modifications. Traces of reactions determined by mass spectrometric analysis at the representative coupling steps in stage 2 confirm the selective construction of a predetermined sequence of metal centers along with the peptide backbone. The WSMOCA cleaved from the resin at the end of stage 2 has a certain level of solubility in aqueous media dependent on the pH value and/or salt content, which is useful for the purification of the compound.

Synthesis of a Water-soluble Metal&amp;#8211;Organic Complex Array

A potential general method for the synthesis of water-soluble multimetallic peptidic arrays containing a predetermined sequence of metal centers is presented.

We demonstrate a method for the synthesis of a water-soluble multimetallic peptidic array containing a predetermined sequence of metal centers such as ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...

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, ...

Microfluidic Preparation of Liquid Crystalline Elastomer Actuators

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation usually consists in the formation of droplets containing low molar mass liquid crystals at elevated temperatures. Subsequently, these particle precursors are oriented in the flow field of the capillary and solidified by a crosslinking polymerization, which produces the final actuating particles. The optimization of the process is necessary to obtain the actuating particles and the proper variation of the process parameters (temperature and flow rate) and allows variations of size and shape (from oblate to strongly prolate morphologies) as well as the magnitude of actuation. In addition, it is possible to vary the type of actuation from elongation to contraction depending on the director profile induced to the droplets during the flow in the capillary, which again depends on the microfluidic process and its parameters. Furthermore, particles of more complex shapes, like core-shell structures or Janus particles, can be prepared by adjusting the setup. By the variation of the chemical structure and the mode of crosslinking (solidification) of the liquid crystalline elastomer, it is also possible to prepare actuating particles triggered by heat or UV-vis irradiation.

This article describes the microfluidic process and parameters to prepare actuating particles from liquid crystalline elastomers. This process allows the preparation of actuating particles and the variation of their size and shape (from oblate to strongly prolate, core-shell, and Janus morphologies) as well as the magnitude of actuation.

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation ...

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. ...

Efficient Synthesis of Polyfunctionalized Benzenes in Water via Persulfate-promoted Benzannulation of &#945;,&#946;-Unsaturated Compounds and Alkynes

Benzannulation reactions represent an effective protocol to transform acyclic building blocks into structurally varied benzene skeletons. Despite classical and recent approaches toward functionalized benzenes, in water metal-free methods remains a challenge and represents an opportunity to expand even more the set of tools used to synthesize polysubstituted benzene compounds. This protocol describes an operationally simple experimental setup to explore the benzannulation of &#945;,&#946;-unsaturated compounds and alkynes to afford unprecedented functionalized benzene rings in high yields. Ammonium persulfate is the reagent of choice and brings notable advantages as stability and easy handling. Moreover, the use of water as a solvent and the absence of metals impart more sustainability to the method. A modified workup procedure that avoids the use of drying agents also adds convenience to the protocol. The purification of the products is performed using only a plug of silica. The substrate scope is currently limited to terminal alkynes and &#945;,&#946;-unsaturated aliphatic compounds.

Efficient Synthesis of Polyfunctionalized Benzenes in Water via Persulfate-promoted Benzannulation of &#945;,&#946;-Unsaturated Compounds and Alkynes

A persulfate-promoted metal-free benzannulation of &#945;,&#946;-unsaturated compounds and alkynes in water toward the synthesis of unprecedented polyfunctionalized benzenes is reported.