Name: preparation of hydrophobic metal-organic frameworks via plasma enhanced chemical vapor deposition of perfluoroalkanes for the removal of ammonia
Uploaded: 2013-10-10T22:00:00
Description: Watch this Scientific Journal Video about Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia at JoVE.com

The authors thank the Defense Threat Reduction Agency for funding under project number BA07PRO104, Martin Smith, Corrine Stone, and Colin Willis of the Defence Science and Technology Laboratory (DSTL) for their expertise in low pressure plasma technology, and Matthew Browe and Wesley Gordon of the Edgewood Chemical Biological Center (ECBC) for microbreakthrough testing and contact angle measurements, respectively.

1. Cu-BTC Synthesis and Preparation
<ol>
	<li>Stir 12.5 ml of deionized water and 12.5 ml of dimethylformamide in a 100 ml screw cap jar for approximately 5 min.</li>
	<li>Add 0.87 g (3.6 mmol) copper(II) nitrate trihydrate followed by 0.50 g (2.4 mmol) of trimesic acid to the solution in the jar and stir for approximately 5 min. The solution will turn blue in color. Place the capped jar in a preheated oven at 120 &#176;C for approximately 24 hr.</li>
	<li>Remove the jar from the oven. Once the jar has cooled to room t...

<ol>
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Mater. 24, 4010-4013 (2012).</li><li>Li, 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=Enhanced+Hydrostability+in+Ni-Doped+MOF-5.">Enhanced Hydrostability in Ni-Doped MOF-5.</a> Inorg. Chem. 51, 9200-9207 (2012).</li><li>Jasuja, H., Huang, Y. -. g., Walton, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adjusting+the+Stability+of+Metal+-+Organic+Frameworks+under+Humid+Conditions+by+Ligand+Functionalization.">Adjusting the Stability of Metal - Organic Frameworks under Humid Conditions by Ligand Functionalization.</a> Langmuir. 28, 16874-16880 (2012).</li><li>Jasuja, H., Burtch, N. C., Huang, Y. -. g., Cai, Y., Walton, K. 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W., Andreu, A., Falco, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+studies+of+novel+hydrophobic+active+carbons.">Surface studies of novel hydrophobic active carbons.</a> Appl. Surf. Sci. 257, 2912-2919 (2011).</li><li>Poire, E., 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=Modification+of+active+carbon+by+hydrophobic+plasma+plymers.">Modification of active carbon by hydrophobic plasma plymers.</a> Plasma Deposition of Polymeric Thin Films. 54, 185-196 (1994).</li><li>Hozumi, A., Takai, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+ultra+water-repellent+films+by+microwave+plasma-enhanced+CVD.">Preparation of ultra water-repellent films by microwave plasma-enhanced CVD.</a> Thin Solid Films. 303 (97), 222-225 (1997).</li><li>Dolbier, 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=.">.</a> Guide to Fluorine NMR for Organic Chemists. , (2009).</li><li>Maricq, M. M., Waugh, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=NMR+IN+ROTATING+SOLIDS.">NMR IN ROTATING SOLIDS.</a> J. Chem. Phys. 70, 3300-3316 (1979).</li><li>Kim, M., Cahill, J. F., Su, Y., Prather, K. A., Cohen, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postsynthetic+ligand+exchange+as+a+route+to+functionalization+of+'inert'+metal-organic+frameworks.">Postsynthetic ligand exchange as a route to functionalization of 'inert' metal-organic frameworks.</a> Chem. Sci. 3, 126-130 (2012).</li><li>d'Agostino, R., 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> Advanced Plasma Technology. , (2008).</li><li>DeCoste, J. B., 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=+The+effect+of+water+adsorption+on+the+structure+of+the+carboxylate+containing+metal-organic+frameworks+Cu-BTC,+Mg-MOF-74,+and+UiO-66."> The effect of water adsorption on the structure of the carboxylate containing metal-organic frameworks Cu-BTC, Mg-MOF-74, and UiO-66.</a> J. Mater. Chem. A. , (2013).</li></ol>

The synthesis of Cu-BTC, as in most MOFs, can be heavily dependent on the ratio of reactants used and the temperature the synthesis is carried out at. Varying the temperature or solvent used in synthesis has been shown to produce different morphologies of a MOF structure20. Therefore it is of strong importance to follow the procedure set forth in the literature for any MOF being synthesized. Furthermore, one should consider the reactants, solvents, and synthesis conditions when choosing a vessel in which to co...

Metal-organic frameworks (MOFs) have become a leading class of porous materials for toxic gas removal1-3. MOFs have an unprecedented ability to tailor functionality for targeted chemical interaction. Cu-BTC (also known as HKUST-1 or Cu3(BTC)2) has been previously found to have an exceptionally high ammonia loading; however, this is at a cost of the material&#39;s structural stability4 . Further studies on Cu-BTC have indicated that moisture itself is capable of degrading the MOF structure, rendering it ineffective for many potential applications5,6,21. The structural instability of certain carboxylate containing MOFs in the presence of liquid water or high humidity has been a major deterrent to use in commercial or industrial applications7 .
It would be most ideal for MOFs used for chemical removal to have inherent stability in the presence of humidity. However, many MOFs with superior stability, such as UiO-66, have poor chemical removal capabilities, while many MOFs with open metal sites like MOF-74 and Cu-BTC have superior chemical removal capabilities2,4,8,9. The open metal sites in MOF-74 and Cu-BTC enhance the uptake of toxic gases such as ammonia, but these sites are also susceptible to binding water, poisoning the active sites and in many cases leading to structural breakdown. In order to preserve the chemical properties of a water unstable MOF, various attempts to enhance the water stability of MOFs have been made. MOF-5 has been shown to have an enhancement in moisture resistance upon thermal treatment, by creating a carbonaceous layer around the MOF; however, the increased hydrophobicity is at the expense of surface area and ultimately functionality10. MOF-5 has also been shown to have its hydrostability increased through doping with Ni2+ ions11. Furthermore, 1,4-diazabicyclo[2.2.2]octane containing MOFs (also known as DMOFs) have been used to show the tuning of water stability through incorporation of various pendant groups on the 1,4-benzene dicarboxylate linker12,13.
The lack of hydrostability of certain of MOFs, specifically ones with high toxic gas uptake, led to the use of plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes to create fluorinated groups on the surfaces of the MOF to increase its hydrophobicity14. This technique offers the unique benefit that it can be used to alter any MOF containing aromatic hydrogens, as well as other potential functional groups on the inner surfaces of MOFs. However, the technique can be difficult to control due to the formation of highly reactive radicals in the plasma. The radicals not only react with the aromatic hydrogen atoms, but also with CFx groups already reacted onto the MOF surfaces. Careful control of the procedure is necessary to ensure pore blockage does not occur, rendering the MOF ineffective. This technique has been used by others to alter the wetting properties of carbon materials; however, to our knowledge it had never previously been used to enhance hydrostability of microporous material.15,16.

<table border="1">
	<tbody>
		<tr>
			<td>Name of Material/ Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr>
			<td>Copper (II) Nitrate Trihydrate</td>
			<td>Sigma-Aldrich</td>
			<td>61194</td>
			<td></td>
		</tr>
		<tr>
			<td>Trimesic acid</td>
			<td>Sigma-Aldrich</td>
			<td>482749</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Sigma-Aldrich</td>
			<td>130147</td>
			<td></td>
		</tr>
		<tr>
			<td>Dimethyl Formamide</td>
			<td>Sigma-Aldrich</td>
			<td>319937</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichloromethane</td>
			<td>Sigma-Aldrich</td>
			<td>187332</td>
			<td></td>
		</tr>
		<tr>
			<td>Hexafluoroethane</td>
			<td>Synquest Labs</td>
			<td>1100-2-05</td>
			<td></td>
		</tr>
		<tr>
			<td>Femto-Plasma System</td>
			<td>Diener Electronic</td>
			<td>Basic unit type B</td>
			<td></td>
		</tr>
		<tr>
			<td>Plasma Generator</td>
			<td>Diener Electronic</td>
			<td>Type D</td>
			<td>0-100 W at 13.56 MHz</td>
		</tr>
		<tr>
			<td>Rotary Vane Pump for Plasma System</td>
			<td>Leybold</td>
			<td>D16BCS PFPE</td>
			<td>Appropriate for corrosive gases</td>
		</tr>
		<tr>
			<td>Powder Treatment Device</td>
			<td>Diener Electronic</td>
			<td>Option 5.9</td>
			<td>Glass bottle and rotating devise within plasma system</td>
		</tr>
		<tr>
			<td>Environmental Chamber</td>
			<td>Associated Environmental Systems</td>
			<td>HD-205</td>
			<td></td>
		</tr>
		<tr>
			<td>Gas Chromatograph</td>
			<td>Hewlet Packard</td>
			<td>HP5890 Series II</td>
			<td></td>
		</tr>
		<tr>
			<td>Photoionization Detector</td>
			<td>O-I Analytical</td>
			<td>4430/5890</td>
			<td></td>
		</tr>
		<tr>
			<td>Photoionization Detector Lamp</td>
			<td>Excilitis</td>
			<td>FK-794U</td>
			<td></td>
		</tr>
		<tr>
			<td>Water bath</td>
			<td>NESLAB</td>
			<td>RTE-111</td>
			<td></td>
		</tr>
		<tr>
			<td>Fritted glass tubes</td>
			<td>CDA Analytical</td>
			<td>MX062101</td>
			<td>Dynatherm sampling tubes</td>
		</tr>
	</tbody>
</table>

preparation of hydrophobic metal-organic frameworks via plasma enhanced chemical vapor deposition of perfluoroalkanes for the removal of ammonia

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high surface area microporous materials, such as metal-organic frameworks (MOFs), unique challenges present themselves for PECVD treatments. Herein the protocol for development of a MOF that was previously unstable to humid conditions is presented. The protocol describes the synthesis of Cu-BTC (also known as HKUST-1), the treatment of Cu-BTC with PECVD of perfluoroalkanes, the aging of materials under humid conditions, and the subsequent ammonia microbreakthrough experiments on milligram quantities of microporous materials. Cu-BTC has an extremely high surface area (~1,800 m2/g) when compared to most materials or surfaces that have been previously treated by PECVD methods. Parameters such as chamber pressure and treatment time are extremely important to ensure the perfluoroalkane plasma penetrates to and reacts with the inner MOF surfaces. Furthermore, the protocol for ammonia microbreakthrough experiments set forth here can be utilized for a variety of test gases and microporous materials.

Within the representative results the authors chose to display the characteristics of a 0.50 g sample of Cu-BTC treated with hexafluoroethane (C2F6) for 4 hr at a pressure of 0.30 mbar and a plasma power of 50 W. MOFs treated with a perfluoroalkane plasma under adequate conditions should display enhanced hydrophobicity. This can be demonstrated by placing the powder on top of liquid water and determining if the sample floats or measuring the contact angle water on a pressed pellet as seen in <strong...

Watch this Scientific Journal Video about Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia at JoVE.com

Preparation of Hydrophobic Metal-Organic Frameworks via Plasma Enhanced Chemical Vapor Deposition of Perfluoroalkanes for the Removal of Ammonia

Herein the procedures for plasma enhanced chemical vapor deposition of perfluoroalkanes on microporous materials such as metal-organic frameworks to enhance their stability and hydrophobicity are described. Furthermore, breakthrough testing of milligram quantities of samples is described in detail.

Plasma enhanced chemical vapor deposition (PECVD) of perfluoroalkanes has long been studied for tuning the wetting properties of surfaces. For high ...

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