Expt. 2. Synthesis of Bis(tetraethylammonium) Tetrachlorocobaltate (II)
Expt. 2. Synthesis of Bis(tetraethylammonium) Tetrachlorocobaltate (II)
Expt. 2. Synthesis of Bis(tetraethylammonium) Tetrachlorocobaltate (II)
Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Chem 151L, Spring 2015<br />
<strong>Expt</strong>. <strong>2.</strong> <strong>Synthesis</strong> and Anion-Exchange <strong>of</strong> a Metal-Organic Framework<br />
Metal-organic frameworks (MOFs) are covalent networks where metal atoms or<br />
clusters are connected by organic linkers. 1 These extended structures can be<br />
1-D chains, 2-D layers or 3-D frameworks. The materials are <strong>of</strong> interest for a variety <strong>of</strong><br />
potential applications including gas storage, sensors, catalysis and solid state batteries.<br />
An example is the MOF known as SLUG-21 (Figure 1),<br />
[Ag 2 (4,4’-bipy) 2+ 2 ][ – O 3 SCH 2 CH 2 SO – 3 ]·4H 2 O, where bipy is bipyridine, (C 5 H 4 N) 2 . 2 In this<br />
lab, you will synthesize a related MOF known as silver bipyridine nitrate (SBN,<br />
[Ag(4,4’-bipy) + ][NO – 3 ]). 3 This material is a rare example <strong>of</strong> a host material that<br />
possesses a charge. Nitrate anions reside between the layers and may be reversibly<br />
exchanged out <strong>of</strong> the material for other anions in solution including pollutants such as<br />
perchlorate, chromate and pertechnetate.<br />
Figure 1. SLUG-21 displays reversible, selective uptake <strong>of</strong> a variety <strong>of</strong><br />
inorganic and organic anions. Left: side view <strong>of</strong> the cationic layers and<br />
interlayer anions; right: view <strong>of</strong> one layer <strong>of</strong> -stacked Ag-bipy + polymers.<br />
Week 1: Place a stir bar and 10 mL <strong>of</strong> distilled water in a beaker, followed by<br />
0.10 g silver nitrate. With manual stirring, add 0.10 g <strong>of</strong> 4,4’-bipyridine. Allow to<br />
mechanically stir for at least 50 minutes, then parafilm the beaker and leave in your<br />
drawer until the following lab period.<br />
Week 2: At the start <strong>of</strong> the following lab period, filter the product, rinsing with<br />
acetone. Weigh the product and calculate the percent yield. Place ~ 50 mg <strong>of</strong> the<br />
product in a vial and label with your names, TA name and “as-synthesized SBN”. Place<br />
80 mg <strong>of</strong> the product in a beaker containing 50 mL distilled water. Add 0.25 millimoles <strong>of</strong><br />
the anion that has been assigned to you and your lab partner. Stir mechanically for at<br />
least 1 hour. Filter the product into a clean flask and analyze the liquid by FTIR or UV-<br />
Vis, depending on the anion you are studying. Place the solid in a labelled vial (names,
TA name and “SBN-anion”, where “anion” is the anion formula) for PXRD analysis. Your<br />
TA will collect the powder X-ray diffraction (PXRD) data before the next lab period.<br />
Questions:<br />
1) Write a balanced set <strong>of</strong> equations for the synthesis steps and determine the yield.<br />
2) Closely compare the PXRD patterns before and after the exchange. If you have UV-<br />
Vis data, calculate the percent exchange.<br />
3) Why was excess anion used for the exchange?<br />
4) What other characterization techniques could be used to monitor the exchange if they<br />
were available?<br />
References<br />
1) Zhou, H.-C.; Long, J. R.; Yaghi, O. M. Chem. Rev. 2012, 112, 673-674 and journal<br />
articles within that special issue on MOFs.<br />
2) Fei, H.; Bresler, M. R.; Oliver, S. R. J. J. Am. Chem. Soc., 2011, 133, 11110–11113.<br />
3) O. M. Yaghi, H. L., J. Am. Chem. 1996, 118, 295-296.