Name: microfluidic-based synthesis of covalent organic frameworks (cofs): a tool for continuous production of cof fibers and direct printing on a surface
Uploaded: 2017-07-10T11:30:00
Description: Watch this Scientific Journal Video about Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface at JoVE.com

The authors acknowledge the Swiss National Science Foundation (SNF) for financial support through project no. 200021_160174.

1. Master Mold Fabrication
<ol>
	<li>Perform the photolithographic fabrication of a 4 inch silicon master mold as described in detail previously19; the master mold used in this study has been fabricated using the same protocol. 
	NOTE: Microfluidic devices are typically fabricated through a multi-step process. The first step is the design of the microfluidic channel using a conventional drawing software. Then, high-resolution film photomasks containing the microfluidic network are produced ...

<ol>
	<li>Cote, A. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porous,+crystalline,+covalent+organic+frameworks.">Porous, crystalline, covalent organic frameworks.</a> Science. 310, 1166-1170 (2005).</li><li>Ding, S. Y., Wang, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Covalent+organic+frameworks+(COFs):+from+design+to+applications.">Covalent organic frameworks (COFs): from design to applications.</a> Chem Soc Rev. 42, 548-568 (2013).</li><li>Huang, N., Wang, P., Jiang, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Covalent+organic+frameworks:+a+materials+platform+for+structural+and+functional+designs.">Covalent organic frameworks: a materials platform for structural and functional designs.</a> Nat Rev Mater. 1, 16068 (2016).</li><li>Xu, H., Gao, J., Stable Jiang, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=crystalline,+porous,+covalent+organic+frameworks+as+a+platform+for+chiral+organocatalysts.">crystalline, porous, covalent organic frameworks as a platform for chiral organocatalysts.</a> Nat Chem. 7, 905-912 (2015).</li><li>Wan, S., Guo, J., Kim, J., Ihee, H., Jiang, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Belt-Shaped,+Blue+Luminescent,+and+Semiconducting+Covalent+Organic+Framework.">A Belt-Shaped, Blue Luminescent, and Semiconducting Covalent Organic Framework.</a> Angew Chem Int Edit. 47, 8826-8830 (2008).</li><li>Rodriguez-San-Miguel, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Crystalline+fibres+of+a+covalent+organic+framework+through+bottom-up+microfluidic+synthesis.">Crystalline fibres of a covalent organic framework through bottom-up microfluidic synthesis.</a> Chem Commun. 52, 9212-9215 (2016).</li><li>Bisbey, R. P., DeBlase, C. R., Smith, B. J., Dichtel, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Two-dimensional+Covalent+Organic+Framework+Thin+Films+Grown+in+Flow.">Two-dimensional Covalent Organic Framework Thin Films Grown in Flow.</a> J Am Chem Soc. 138, 11433-11436 (2016).</li><li>Spitler, E. L., Dichtel, W. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lewis+acid-catalysed+formation+of+two-dimensional+phthalocyanine+covalent+organic+frameworks.">Lewis acid-catalysed formation of two-dimensional phthalocyanine covalent organic frameworks.</a> Nat Chem. 2, 672-677 (2010).</li><li>Keskin, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adsorption,+Diffusion,+and+Separation+of+CH4/H-2+Mixtures+in+Covalent+Organic+Frameworks:+Molecular+Simulations+and+Theoretical+Predictions.">Adsorption, Diffusion, and Separation of CH4/H-2 Mixtures in Covalent Organic Frameworks: Molecular Simulations and Theoretical Predictions.</a> J Phys Chem C. 116, 1772-1779 (2012).</li><li>Tilford, R. W., Mugavero, S. J., Pellechia, P. J., Lavigne, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tailoring+microporosity+in+covalent+organic+frameworks.">Tailoring microporosity in covalent organic frameworks.</a> Adv Mater. 20, 2741-2746 (2008).</li><li>Hasegawa, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+porous+coordination+polymer+functionalized+with+amide+groups+based+on+tridentate+ligand:+Selective+sorption+and+catalysis.">Three-dimensional porous coordination polymer functionalized with amide groups based on tridentate ligand: Selective sorption and catalysis.</a> J Am Chem Soc. 129, 2607-2614 (2007).</li><li>Das, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemical+sensing+in+two+dimensional+porous+covalent+organic+nanosheets.">Chemical sensing in two dimensional porous covalent organic nanosheets.</a> Chem Sci. 6, 3931-3939 (2015).</li><li>Guo, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Conjugated+organic+framework+with+three-dimensionally+ordered+stable+structure+and+delocalized+pi+clouds.">Conjugated organic framework with three-dimensionally ordered stable structure and delocalized pi clouds.</a> Nat Commun. 4, 2736 (2013).</li><li>Furukawa, H., Yaghi, O. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Storage+of+Hydrogen,+Methane,+and+Carbon+Dioxide+in+Highly+Porous+Covalent+Organic+Frameworks+for+Clean+Energy+Applications.">Storage of Hydrogen, Methane, and Carbon Dioxide in Highly Porous Covalent Organic Frameworks for Clean Energy Applications.</a> J Am Chem Soc. 131, 8875-8883 (2009).</li><li>Xu, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemically+active,+crystalline,+mesoporous+covalent+organic+frameworks+on+carbon+nanotubes+for+synergistic+lithium-ion+battery+energy+storage.">Electrochemically active, crystalline, mesoporous covalent organic frameworks on carbon nanotubes for synergistic lithium-ion battery energy storage.</a> Sci Rep-Uk. 5, 8225 (2015).</li><li>El-Kaderi, H. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Designed+synthesis+of+3D+covalent+organic+frameworks.">Designed synthesis of 3D covalent organic frameworks.</a> Science. 316, 268-272 (2007).</li><li>Ruigomez, A. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+On-Surface+Patterning+of+a+Crystalline+Laminar+Covalent+Organic+Framework+Synthesized+at+Room+Temperature.">Direct On-Surface Patterning of a Crystalline Laminar Covalent Organic Framework Synthesized at Room Temperature.</a> Chem Eur J. 21, 10666-10670 (2015).</li><li>Segura, J. L., Mancheno, M. J., Zamora, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Covalent+organic+frameworks+based+on+Schiff-base+chemistry:+synthesis,+properties+and+potential+applications.">Covalent organic frameworks based on Schiff-base chemistry: synthesis, properties and potential applications.</a> Chem Soc Rev. 45, 5635-5671 (2016).</li><li>Abrishamkar, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+Pneumatic+Cages:+A+Novel+Approach+for+In-chip+Crystal+Trapping,+Manipulation+and+Controlled+Chemical+Treatment.">Microfluidic Pneumatic Cages: A Novel Approach for In-chip Crystal Trapping, Manipulation and Controlled Chemical Treatment.</a> J Vis Exp. (113), e54193 (2016).</li><li>Duffy, D. C., McDonald, J. C., Schueller, O. J. A., Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+prototyping+of+microfluidic+systems+in+poly(dimethylsiloxane).">Rapid prototyping of microfluidic systems in poly(dimethylsiloxane).</a> Anal Chem. 70, 4974-4984 (1998).</li><li>Rubio-Martinez, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Freezing+the+Nonclassical+Crystal+Growth+of+a+Coordination+Polymer+Using+Controlled+Dynamic+Gradients.">Freezing the Nonclassical Crystal Growth of a Coordination Polymer Using Controlled Dynamic Gradients.</a> Adv Mater. 28, 8150-8155 (2016).</li><li>Liu, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Catalytic+Chiral+Gel+Microfluidic+Reactor+Assembled+via+Dynamic+Covalent+Chemistry.">A Catalytic Chiral Gel Microfluidic Reactor Assembled via Dynamic Covalent Chemistry.</a> Chem Sci. 6, 2292-2296 (2015).</li><li>Puigmarti-Luis, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Stepwise+Template+Growth+of+Functional+Nanowires+from+an+Amino+Acid-Supported+Framework+in+a+Microfluidic+Chip.">Stepwise Template Growth of Functional Nanowires from an Amino Acid-Supported Framework in a Microfluidic Chip.</a> ACS Nano. 8 (1), 818-826 (2014).</li></ol>

The microfluidic-based synthetic method reported here provides a novel and simple approach for direct printing of COF materials on surfaces. Synthesis is performed using a single-layer microfluidic device, comprised of a microfluidic PDMS chip bonded to a glass coverslip. The fabrication of the microfluidic device can be achieved through conventional casting of PDMS against a silicon master mold and subsequently bonding the PDMS with the imprinted microchannels against a glass coverslip.
For t...

Covalent organic frameworks (COFs) are a well-established class of porous and crystalline material in which the organic building blocks are firmly held together by covalent bonds1,2,3,4,5. COFs are typically assembled following supramolecular chemistry principles, where the constituent molecular building blocks are selectively reacted to define a final and predetermined porous assembly. Such an approach allows the synthesis of materials with controlled and ordered structure (e.g.,with defined pore dimensions) and composition3,6,7,8. Compared to other porous materials, COFs are unique since they are comprised of light elements (C, H, B, N and O) and have tunable porosities1,5. Inspired by these unique and intrinsic characteristics, COFs have been assessed for potential application in chemical separations9, gas storage10and catalysis11, sensors12, optoelectronics13, clean energy technologies14 and electrochemical energy devices15.
To date, the vast majority of methods used for the preparation of COF materials are based on solvothermal self-condensation and co-condensation reactions, where high temperatures and pressures are the standard. Although COFs are thermally robust, they commonly suffer from limited processability, i.e., COFs are usually insoluble and unprocessable crystalline powders, and this significantly limits their use in a range of potential and practical applications2,6,8,16,17. Despite the remarkable progress made in COF synthesis, a major challenge in the field is to develop a method enabling the preparation of COFs in appropriate reaction conditions (e.g., temperature and pressure), which can then facilitate their processability on surfaces.
Recently, studies have shown that Shiff-base chemistry can be used to synthesize an imine-based COF at room temperature. The COF produced, named RT-COF-1, forms due to the fast and efficient reaction between 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 1,3,5-benzenetricarbaldehyde (BTCA)17 (Figure 1A). The efficacy of this synthetic method was demonstrated by the direct printing of micron and submicron patterns of RT-COF-1 on both rigid and flexible surfaces using lithography or inkjet printing techniques. More recently, and making use of microfluidics, we have demonstrated an effective approach for the continuous synthesis of fibers of the same imine-based COF hereafter called MF-COF6. Unlike other reported synthetic approaches for the generation of COFs18, this microfluidic-based synthetic method enabled the rapid synthesis of MF-COF fibers at ambient temperatures and pressures within a few seconds. Furthermore, and owing to the mechanical stability of the synthesized MF-COF fibers, we have demonstrated how such microfluidic-based method can enable the direct printing of 2D and 3D structures on surfaces. Herein, we demonstrate that this method can be used to draw COF structures on various surfaces having different chemical and physical properties. We believe that this novel method opens new avenues for the well-controlled patterning and direct printing of COFs in different orientations and on various surfaces.

<table border="0" cellpadding="0" cellspacing="0" width="1147">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">High resolution film masks</td>
			<td style="width:252px;">Microlitho, UK</td>
			<td style="width:189px;">-</td>
			<td style="width:371px;">Features down to 5um</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Silicon wafers</td>
			<td style="width:252px;">Silicon Materials Inc., Germany</td>
			<td style="width:189px;">4&#34; Silicon Wafers</td>
			<td>Front surface: polished, back surface: etched</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Silicone Elastomer KIT (PDMS)</td>
			<td style="width:252px;">Dow Corning, USA</td>
			<td style="width:189px;">Sylgard 184</td>
			<td>-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Chlorotrimethylsilane</td>
			<td style="width:252px;">Sigma-Aldrich, Switzerland</td>
			<td style="width:189px;">386529</td>
			<td>&#8805;97%, CAUTION: Handle it only under fume hood.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Biopsy puncher</td>
			<td style="width:252px;">Miltex GmBH, Germany</td>
			<td style="width:189px;">33-31A-P/25</td>
			<td>1.5 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Glass coverslip</td>
			<td style="width:252px;">Menzel-Glaser, Germany</td>
			<td style="width:189px;">BB024040SC</td>
			<td>24 mm &#215; 40 mm, #5</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Plasma generator instrument</td>
			<td style="width:252px;">Diener</td>
			<td style="width:189px;">Zepto B</td>
			<td>Frequency: 40 kHz and plasma generator power: 0-30 W</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">PTFE tubing</td>
			<td style="width:252px;">PKM SA, Switzerland</td>
			<td style="width:189px;">AWG-TFS-XXX</td>
			<td style="width:371px;">AWG 20TFS, roll of 100 m</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">neMESYS Syringe Pumps</td>
			<td style="width:252px;">Cetoni GmbH, Germany</td>
			<td style="width:189px;">Low Pressure (290N)</td>
			<td>-</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Disposable Cup</td>
			<td style="width:252px;">Semadeni, Switzerland</td>
			<td style="width:189px;">8323</td>
			<td>PS, 200 ml</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Plastic Spatula</td>
			<td style="width:252px;">Semadeni, Switzerland</td>
			<td style="width:189px;">3340</td>
			<td>L &#215; W : 135 mm x 14 mm</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Disposable Scalpels</td>
			<td style="width:252px;">B. Braun, Switzerland</td>
			<td style="width:189px;">233-5320</td>
			<td>Nr. 20</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Disposable Syringes</td>
			<td style="width:252px;">VWR, Switzerland</td>
			<td style="width:189px;">613-3951</td>
			<td>5 ml, Discardit II</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">Acetic Acid</td>
			<td style="width:252px;">Sigma-Aldrich, Switzerland</td>
			<td style="width:189px;">695092-500</td>
			<td>&#62;=99.7%, CAUTION: Handle it only under fume hood.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">1,3,5-benzenetricarbaldehyde</td>
			<td style="width:252px;">Aldrich-Fine Chemicals</td>
			<td style="width:189px;">753491</td>
			<td>97%</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:336px;">1,3,5-Tris(4-aminophenyl)benzene</td>
			<td style="width:252px;">Tokyo Chemical Industry</td>
			<td style="width:189px;">T2728-5G</td>
			<td>&#62;93.0%</td>
		</tr>
	</tbody>
</table>

microfluidic-based synthesis of covalent organic frameworks (cofs): a tool for continuous production of cof fibers and direct printing on a surface

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The first COF was reported in 2005 with much effort centered on the establishment of new synthetic routes for its preparation. To date, most available synthetic methods for COF synthesis are based on bulk mixing under solvothermal conditions. Therefore, there is increasing interest in developing systematic protocols for COF synthesis that provide for fine control over reaction conditions and improve COF processability on surfaces, which is essential for their use in practical applications. Herein, we present a novel microfluidic-based method for COF synthesis where the reaction between two constituent building blocks, 1,3,5-benzenetricarbaldehyde (BTCA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB), takes place under controlled diffusion conditions and at room temperature. Using such an approach yields sponge-like, crystalline fibers of a COF material, hereafter called MF-COF. The mechanical properties of MF-COF and the dynamic nature of the approach allow the continuous production of MF-COF fibers and their direct printing onto surfaces. The general method opens new potential applications requiring advanced printing of 2D or 3D COF structures on flexible or rigid surfaces.

The microfluidic device used in our investigations is fabricated using conventional PDMS replica molding20 and incorporates four microfluidic inlet channels that merge into a main microchannel. The final microfluidic device consists of a structured PDMS layer and a glass coverslip used to close the imprinted microchannels, as shown in Figure 1B.
<img alt="Figure 1" class="xfi...

Watch this Scientific Journal Video about Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface at JoVE.com

Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

We present a novel microfluidic-based method for synthesis of covalent organic frameworks (COFs). We demonstrate how this approach can be used to produce continuous COF fibers, and also 2D or 3D COF structures on surfaces.

Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The ...

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