To begin, cool the cold trap of the Schlenk line by placing a Dewar flask filled with liquid nitrogen around it. Use a towel to cover the top of the Dewar flask. This will slow down the evaporation of the liquid nitrogen during the experiment, open the bubbler to a light flow of inert gas, either nitrogen or argon.
Roll a piece of weighing paper into a cone to use as a solid addition funnel and place it in the tap opening of the 10-milliliter flask. Ensure the bottom of the cone is inserted far enough that it extends past the hose attachment. Weigh the tetrakis triphenylphosphine palladium-0 into the 10-milliliter flask.
Repeat this step for triphenylphosphine. After disposing the weighing paper cone, screw the polytetrafluoroethylene, or PTFE tap, onto the 10-milliliter flask. Similarly, weigh the tetratopic phosphine linker tin-1 into a separate 10-milliliter flask.
To place the reagents under an inert atmosphere, connect hose from the Schlenk line to each of the 10-milliliter flasks. Open the PTFE tap just enough that the vessel is open to the hose. Open both the flasks to the vacuum and wait for five minutes.
Close the tap on each flask and then close each hose to the vacuum. Switch the hoses to the inert gas and then slowly open the tap on each flask to backfill it with inert gas. Repeat these steps two more times for a total of three cycles.
Remove the PTFE tap and replace it with a septum for each flask under a positive pressure of inert gas sufficient to prevent air from entering the flask. Use a syringe and needle to transfer 1.5 milliliters of dry and deoxygenated toluene into the flask containing the tetrakis triphenylphosphine palladium-0 and triphenylphosphine. Then, transfer 1.5 milliliters of dry and deoxygenated methylene chloride to the flask.
Swirl the flask until all the solids have dissolved. Next, transfer three milliliters of dry and deoxygenated methylene chloride into the flask containing the tetratopic phosphine linker tin-1 and swirl the flask until all the solid has dissolved. Transfer the entire tin-1 linker solution into the flask containing the tetrakis triphenylphosphine palladium-0 and triphenylphosphine and swirl the solution for 30 seconds to thoroughly mix it.
Replace the septum with the PTFE tap under a positive pressure of inert gas and seal the flask. Sonicate the reaction solution at 40 kilohertz for an additional 30 seconds. Place the sealed flask into a preheated oil bath at 60 degrees Celsius and leave it for 24 hours without agitating it.
To isolate the MOF product, remove the flask from the oil bath and allow it to cool to room temperature. Set up a vacuum filtration apparatus using a small Buchner funnel and filter paper. Remove the PTFE tap from the flask and then use a pipette to transfer the total volume of the suspension to the filter.
Rinse the solid with two milliliters of deoxygenated 3:1 methylene chloride/toluene solution. Repeat the step two more times and allow the solid to dry on the filter paper for three minutes. Scrape the solid into a pre-weighed vial and then weigh the vial to obtain the yield of the low-valent MOF.
The synthesis of three-dimensional low valent MOFs using tetratopic phosphine ligands as linkers, palladium-0 and platinum-0 as nodes, and triphenylphosphine as a modulator is shown here. The central atom E can be silicon or tin.
