This method can help answer key questions in the field of metal organic frameworks such as the nature of surface nucleation and MOF adhesion. The main advantage of this technique is that it produces MOF films on fabric during the MOF synthesis rather than requiring additional processing steps to adhere MOF to the fiber. Demonstrating the procedure will be Dennis Lee, a grad student from my laboratory.
First, place a PA-6 fabric sample in a reactor boat. Open the pressure gauge of the ALD reactor and remove the clasp from the reactor cap. Next, turn on manual control in the lab view system.
Close the carrier nitrogen and gate valve on the ALD reactor. Then open the vent nitrogen. The reactor will open and the cap will fall off.
After removing the reactor cap, load the fabric sample into the ALD reactor. Replace the reactor cap. Then open the gate valve.
Following this, open the carrier nitrogen and close the vent. Then turn off manual control. Load the recipe for titanium oxide on fabrics.
Set the recipe to run 300 cycles. Next, set the mass flow controller to 20 cubic feet per minute and the furnace temperature to 90 degrees Celsius. Open the manual valve to the titanium tetrachloride and water.
Close the pressure gauge and replace the clasp on the reactor cap. Then press start on the interface. Upon completion of the recipe, open the pressure gauge.
Remove the clasp from the reactor cap. Then turn on manual control in the system. Following this, close the carrier nitrogen and gate valve on the ALD reactor.
Then open the vent nitrogen. The reactor will open and the cap will fall off. Remove the sample boat.
Reseal the reactor. Add 0.0878 grams of trimesic acid to an 80 milliliter glass beaker. Add 12 milliliters of water and 12 milliliters of ethanol to the beaker.
Then add a magnetic stir bar to the solution and stir until the trimesic acid is fully dissolved. Next, place the solution in a Teflon-lined pressure vessel. Add previously prepared aluminum oxide-coded polypropylene to the solution and prop the fabric on a mesh support so it does not lie flat against the bottom of the vessel.
Following this, seal the pressure vessel and place it in the furnace at 110 degrees Celsius for 24 hours. Add 0.08 grams of zirconium chloride to a 20 milliliter glass scintillation vial. Add 20 milliliters of DMF to the zirconium chloride in five milliliter increments.
Cap the vial between increments and allow the fumes to dissipate. Next, sonicate the solution for one minute. Add 0.062 grams of 2-aminoterephthalic acid and a magnetic stir to the vial.
Stir the solution for five minutes. After stirring, add 25 microliters of deionized water to the vial. Then add 1.33 milliliters of concentrated hydrochloric acid to the vial.
Now submerge the titanium dioxide ALD-coded fabric swatch in the solution and cap the vial. Finally, place the sample in the furnace at 85 degrees Celsius for 24 hours. Scanning electron microscopy showed conformal MOF crystal thin films on all fibers resembling a cobblestone pattern.
When the aluminum oxide was reduced, the film began to break apart as the MOF formed resulting in a patchy coding. A bare polypropylene sample was exposed to MIL-96 synthesis conditions, but XRD showed no detectable MOF on the fibers. Cross-sectional images revealed the 500 cycle aluminum oxide base layer completely reacted while a fraction of the aluminum oxide base layer remained for the 1, 000 and 2, 000 cycle samples.
Cross-sections of the aluminum oxide ALD-coded polypropylene are shown here. Electron dispersion spectroscopy images of the cross-section revealed the carbon-based polypropylene core and predominantly aluminum oxide shell. XRD patterns of the MOF-coded fabric matching the simulated PXRD pattern of MIL-96 are shown here.
Following solvothermal MOF synthesis, XRD patterns revealed UIO-66-amine was present on the fibers. SEM images showed flaky MOF codings on the 50 degree Celsius samples, dense MOF codings on the 90 degree Celsius samples, and sparse MOF codings on the 200 degree Celsius samples. An uncoded PA-6 sample was exposed to UIO-66-amine synthesis conditions resulting in a relatively sparse MOF coding.
After watching this video, you should have a good understanding of how to produce conformal MOF films on ALD-coded substrates.
