Chemical Engineering at the University of Bath
By Shaun Mitchell
From the 10th-14th August 2015 I was part of a group of 4 students researching the hydrogen storage capacity of various MOFs (Metal Organic Frameworks) within the Department of Chemical Engineering at the University of Bath. My MOF was HKUST-1, proper name Copper benzene-1,3,5-tricarboxylate.
I synthesised this over the first two days of my internship. This involved the reaction of copper (II) nitrate hemipentahydate and 1,3,5 benzenetricarboxylic acid, the product of which I then dissolved in DMSO and stirred into some methanol for 30 minutes. As a precipitate failed to emerge as expected, I left it on a hot plate overnight to force a precipitate to emerge as I found this to be effective with a sample of my solution.
The following day I purified my solution which had then precipitated using a centrifuge and then pouring off the liquid leaving the solid product behind. I then added ethanol and repeated the process twice more to ensure the product was as pure as possible. I then left my product to be vacuum dried overnight.
Over the following days after an introduction to the BET equation, which we can use to find the surface area per gram of a substance, we ran an adsorption analysis on our samples to find the amount of nitrogen gas adsobed over varying pressures, using this information I then plotted a graph which closely fitted a straight line, the gradient and y-intercept of which I could use to calculate the ‘monolayer amount’ which I could then multiply by the cross-sectional area of a nitrogen molecule and the avogrado constant to obtain the BET surface area. I calculated the surface area of my sample to be around 1,000 square metres per gram. A large amount, however short of the 2,000 plus square metres per gram required for hydrogen storage.
Fortunately this has been observed in other materials which have managed up to 10,000 square metres per gram, so the future of storing hydrogen in MOFs is promising. However more research is needed into mass producing these MOFs and using them in cars to both replace and work alongside current hydrogen storage technologies.