Synthesis and Characterization of Functionalized Metal-organic Frameworks

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.

The overall goal of the following experiment is to synthesize a pillared paddle wheel metal organic framework or moth that is difficult to obtain de novo using solvent assisted linker exchange or sail, and to activate it via super critical carbon dioxide drying. This is achieved by salvo thermally synthesizing the parent mo, which is easy to access de novo from zinc nitrate hexahydrate NN prime D four perial naphthalene, tetra carboxy diamine, and one four DI bromo 2 3 5 6 Tera four carboxyl benzene in an acidic DMF solution in order to use it as a sale template. As a second step, the crystals of the parent moth are subjected to the sale reaction with the DMF solution of the linker of choice, which yields the desired daughter moth product, Salem five.

Next, the DMF solvent in the pores of Salem five is removed by performing solvent exchange with ethanol and activation with super critical carbon dioxide in order to render the material suitable for applications involving gas absorption. The results show retention of framework to topology incorporation of the daughter linkers into the Salem five framework and prevention of framework collapse upon activation based on powder X-ray diffraction in a spinning capillary proton nuclear magnetic resonance spectroscopy and observation of the crystal images of the activated mth and collection of nitrogen isotherms respectively. Our hope is that this video can provide insight into alternative routes toward the synthesis and activation of challenging moths, as well as alert against calming pitfalls committed when handling fragile moth structures.

Additionally, solvent assisted linker exchange can be applied to a wide range of mouse structures beside the pillar paddle wheel systems on which this video is focused. The main advantage of solvent assisted linker exchange over existing methods is its versatility and deficiency combined with its fassal implementation sale. Ameliorates problems associated with linker solvability and typically leads to an almost quantitative synthesis of the daughter Moff Powder.

X-ray diffraction is a powerful technique to confirm the sail reaction has occurred. The method presented here keeps the crystals in their mother liquor, which ensures the MTH framework remains intact. Demonstrating the procedure will be Dr.Rachel Clit, a postdoc from our lab.

First weigh out 50 milligrams of zinc nitrate Hexahydrate, 37.8 milligrams of DPNI and 64.5 milligrams of B-R-T-C-P-B. Combine all solid ingredients in a four gram vial. Add 10 milliliters of DMF to the vial containing the solid ingredients.

Then using a nine inch paster pipette, add one drop of concentrated hydrochloric acid after tightly capping the vial thoroughly. Mix the ingredients using an ultrasonic bath for about 15 minutes, observing the contents of the vial as they form a suspension. Next, place the vial in an oven at 80 degrees Celsius for two days.

On day one, check the vial to ensure that its contents have completely dissolved. Forming a yellow clear solution on day two, observe yellow tear shaped crystals on the walls and the bottom of the vial. Once the vial has been removed from the oven and cooled to room temperature, use a spatula to gently push the crystals off the vial walls so that they all collect on the floor of the vial.

After allowing the crystals to settle on the floor of the vial, gently remove the reaction solution from the vial using a nine inch past stir pipette without sucking up the crystals into the pipette. Add about five milliliters of fresh DMF to the vial with the crystals to soak them for at least one day in order to remove the acidic reaction solution and any unreactive ingredients trapped in the pores. At this point, prepare a 0.7 millimeter diameter.

Borrow silicate glass capillary by carefully cutting off the closed end so that the top three centimeters of the capillary with the funnel top remains. Dip the narrow cut end of the capillary into melted bees wax. After letting the wax solidify as a plug in the bottom of the capillary, support it in a small amount of modeling clay Using a past air pipette, draw up several milliliters of crystals in solution.

Carefully transfer the crystals and solution to the capillary through the funnel opening. Use a paper towel or tissue to wick away excess solvent. Next, allow the crystals to settle into the small plug of beeswax.

Use a very small piece of modeling clay to seal the top end of the capillary. To prepare for powder X-ray diffraction analysis, remove any mounting devices from the goniometer head and place the capillary supported by modeling clay on top of it. Center the capillary in the x-ray beam to ensure that the plug of crystals does not as it rotates.

Following powder X-ray diffraction analysis, way out 21 milligrams of DPED and transfer it to a two gram vial. After adding five milliliters of DMF to the vial, dissolve the DPED with ultras sonication. Using a six inch past air pipette, collect the bro off crystals and filter them on a NER funnel.

Then disperse about 30 milligrams of the crystals in the previously prepared DPED solution. Place the resulting sail mixture in an oven at 100 degrees Celsius for 24 hours. On the next, check the progress of the sail reaction with proton NMR With a six inch PE pipette.

Remove approximately two to five milligrams of the MOF crystals from the cooled reaction solution. Rinse these crystals by submerging them in a small amount of clean solvent such as DMF in a 1.5 gram vial. Following this, add about one milliliter of deuterated dimethyl sulfoxide to a separate 1.5 gram vial.

Once the crystals have been filtered from the cleaning solution, disperse them in deuterated dimethyl sulfoxide. Then add three drops of deuterated sulfuric acid to the mixture. Thoroughly sonicate the captive vial to obtain a homogenous solution.

When finished, transfer the resulting sample to an NMR tube with a paster pipette. Then collect the NMR spectrum performing 64 scans since the solution is relatively dilute due to the low solubility of the MOF crystals. Following solvent exchange with ethanol, transfer the MOF crystals to an activation dish using a six inch PE pipette.

Then remove as much of the ethanol as possible with a nine inch peor pipette without sucking the crystals up into the pipette. Remove the lid of the activation chamber by unscrewing the three bolts and inspect the chamber for residual moth debris. Using a pair of forceps, insert the activation dish with a moth into the chamber and screw the lid back into its place.

Next, turn the dryer on and open the carbon dioxide tank. Adjust the temperature knob to achieve a temperature between zero and 10 degrees Celsius. Once the temperature is in the correct range, turn up the fill knob.Slowly.

Observe liquid carbon dioxide pouring into the activation dish through the glass window on the chamber lid. To perform the first purge, turn the fill knob up to the mark that reads 15. Then slowly turn up the purge knob until a jet of solvent shoots out from the tube on the side of the instrument.

After letting the purge go on for about five minutes, close the purge knob and turn the fill knob down to the mark that reads five. After eight hours of super critical drying, turn all the knobs off and flip the heat switch on. Once the temperature and pressure exceed the super critical point, connect a flow meter to the tube on the side of the instrument and open the bleed knob.

Adjust the flow to one cubic centimeter per minute. Then remove the flow meter, allowing the carbon dioxide to slowly bleed from the sample the next day. Check that the pressure has dropped to zero PSI.

If the pressure has not dropped to this level, turn up the bleed knob until the desired pressure drop is achieved. After closing the bleed knob turn off the heat and power switches on the instrument shown here is a Broome off crystal and the same crystal transformed into Salem. Five is displayed here.

As is the case with single crystal to single crystal reactions. The crystal size and morphology do not change. However cracks develop on the surface due to the harsh nature of sale rendering the Salem five crystal not amenable to single crystal x-ray diffraction data collection.

When the BROMIUM OV synthesis is applied to the Salem five synthesis, the proton NMR shows absence of DPED. To halt, the functionalized linker interaction Sale is used to access Salem five. A typical sale involving DPNI as a leaving pillar requires less than 24 hours with greater than 99%of the pillar being replaced.

Since many pillared paddle wheel moths lose crystallinity when dry PXRD that employs mounting material on glass produces a pattern that may not contain all the peaks in this case, the peak corresponding to the reflection coming from the C axis direction along which the nitrogen donor pillars lie is the first peak. The first peak position at a lower tooth theta angle signifies the presence of a larger unit cell in the C axis direction. Crystal images of NU 100 upon conventional heat and vacuum activation and upon super critical carbon dioxide drying are shown here.

While the former leads to framework collapse and porosity destruction, super critical carbon dioxide drying leads to A BET surface area of about 6, 140 square meters per gram. Following this procedure, other difficult to synthesize moths can be obtained while preventing their delicate frameworks from degradation during their study and allowing access to their evacuated pores. After watching this video, you should have a good understanding of how to perform some helpful methods for MOF synthesis, characterization and activation towards gas absorption applications.

By preparing powder X-ray diffraction samples and capillaries to be mounted on the diff reflectometer, solvent sensitive crystals of any type can be analyzed without fear of sample degradation.