Synthesis and Characterization of Self-Assembled Metal-Organic Framework Monolayers Using Polymer-Coated Particles

Our laboratory is interested at the intersection of porous solids, specifically metal-organic frameworks and organic polymers. We're really interested in understanding the interface between these two materials and how we can make composites that have new emergent properties that are characteristic of both the porous solid as well as the polymer component. Recently we found a grafting polymer onto the surface of MOF, we could produce composite MOF polymer particle that's self-assembled into ultra thin films.

We call this film self-assembled MOF monolayer or SAMMs. We are now interested in understanding how SAMMs vary, depending on polymer length, particle size, and other characteristics. I've begun to explore the role of polymer molecular weight, polymer composition, and polymer grafting density, as well as particle size and shape on SAMM formation and stability.

I believe this study will be very important for understanding and controlling SAMM formation, stability, and future applications. One interesting feature of SAMMs is that they can be made ultra thin, just one particle layer thick. We are unaware of other particle films this thin that are unsupported by another substrate and freestanding.

This unique property may give SAMMs advantages as both membrane over other films or particle assemblies. We're really interested in continuing to study SAMMs, their self-assembly, and what unique properties make them so stable is ultra thin films. In particular, we're really interested in studying SAMMs as coatings and membranes and their use in challenging separations.

Ultimately, we think SAMMs provide a number of avenues for research that have yet to be explored. To begin, transfer 10 milligrams of catechol-DDMAT into a 20 milliliter vial. Use a graduated cylinder to carefully add five milliliters of chloroform to the vial.

Transfer a UiO-66 water dispersion into a 40 milliliter conical centrifuge tube. Then add the catechol-DDMAT solution into the same tube. Vortex the solutions for three minutes to ensure thorough mixing.

Next, with a graduated cylinder, add 20 milliliters of ethanol to the combined mixture. Shake the tube well to evenly mix the solutions. Centrifuge the mixture at approximately 10, 000 x g for 10 minutes.

Remove the supernatant, then add about 40 milliliters of fresh ethanol to wash the pellet. Sonicate the solution to properly redisperse the particles. After centrifuging again, add five milliliters of DMSO to the tube.

Sonicate the particles again for optimal dispersion. Transfer the solution to a 15 milliliter conical centrifuge tube for storage. To begin, pipet out two milliliters of a UiO-66 DDMAT particle dispersion in DMSO and transfer it into a 10 milliliter round bottom flask located on the stirring plate.

Place a stir bar inside the flask. Begin stirring of the dispersion. Next, pipet 12 microliters of iridium(III)phenylpyridine catalyst stock into the flask.

Now add 0.45 milliliters of the DDMAT stock solutions to the flask while stirring. Next pipet 1.7 milliliters of methyl acrylate into a 20 milliliter vial. With a micropipet, add two milliliters of DMSO to the vial.

Shake the vial to dissolve the methyl acrylate. Slowly introduce the methyl acrylate solution dropwise into the reaction flask. Cease the stirring action.

Then securely seal the flask with a septum. Connect a long needle to a nitrogen supply manifold. Insert the needle through the septum to reach the internal air layer of the flask.

Insert a short needle through the septum to create an outlet. Open the nitrogen valve to degas the solution. Lower the long needle to the bottom of the flask for 15 minutes.

Then raise the needle to the internal air layer. After degassing sequentially, remove the short needle followed by the long needle. Then close the nitrogen valve.

Now place a customized blue light LED photo reactor on the stirring plate after connecting it to the power supply, verify the blue light emission. Reinitiate the stirring of the mixture under light exposure. Cover the upper part of the reactor with aluminum foil to prevent excessive light exposure.

Turn off the LED when the viscosity of the reaction solution increases to the point where it can no longer be stirred. For particle self-assembly, first create a dispersion of the particles in toluene. Carefully drop approximately 10 microliters of the toluene dispersion onto a 60 millimeter wide Petri dish filled with deionized water.

When the toluene on the water's surface has evaporated, use a loop made of copper wire to carefully remove part of the monolayer. After evaporating the remaining co associated water, a freestanding monolayer could be observed. Dropping polymer grafter metal-organic frameworks on water from a concentrated toluene dispersion resulted in an iridescent monolayer.

The use of a copper wire mold to lift the monolayer allowed for the formation of freestanding SAMMs.