History is peppered with stories of scientists simultaneously making discoveries. One of the most famous was, of course, when Newton and Leibniz independently developed calculus, but this also occurred for other huge scientific discoveries, such as Darwin and Wallace both coming up with the theory of evolution and, in chemistry, Scheele and Priestley separately discovering oxygen.

So, perhaps I should not have been so surprised when I saw two papers, published around the same time, both reporting the discovery of the exact same metal-organic framework (MOF).

Two groups both independently created the same MOF using the same linkers

But is this coincidence something to be expected? A curious indication of the massive popularity MOFs have gained? It’s a fame that is well deserved. Their potential is huge due to their remarkable porosity, and they are being explored for applications like gas storage, catalysis, gas separation and sensors.

However, I realised I knew next to nothing about their origin. They have a structure that’s not dissimilar to zeolites, but zeolites occur in nature (that’s how we discovered them), whereas MOF-like structures do not. Were they somehow inspired by zeolites? Were they specifically designed for their applications?

I feared that it might be one of those things that have been forgotten, but a little digging proved me wrong. Although some reports suggest that there’s more than one story, it looks like they were made because, like a lot of great innovation, someone said it couldn’t be done.¹

The majority of molecules are zero- or one-dimensional. Zero-dimensional being your bog standard small molecules, while one-dimensional are periodic structures like polymers. It’s harder, however, to make two-dimensional periodic molecules and, at the time, people were pretty certain that three-dimensional molecules were impossible.

The crystal structure of the MOF

So, MOFs were invented to prove a point. Despite scientists knowing of their existence since the 1950s,² no one really explored what they could be used for until 40 years later (people were still questioning the stability of these materials even a decade ago), when researchers such as Omar Yaghi realised that these things had huge surface areas and began to wonder to what might be done with them.³

Since then, the amount of MOF work has grown almost exponentially and, as Hupp et al’s paper suggests, we’re perhaps now at a stage where their use in vehicles (to replace petrol with methane gas) isn’t too far off.

In energy conscious times, this will provide a bit of relief for countries that have to import their oil and could hopefully also drive petrol prices down. Of course, burning gas should also be cleaner than petrol too.

One final consideration. Hupp’s team note that gas-powered cars are already running in the US, although they don’t use MOFs. In a country that calls ‘petrol’ ‘gas’ does anyone else foresee some sitcom-esque misunderstandings at ‘gas stations’?

Yuandi Li

References

1 M O’Keeffe, Chem. Soc. Rev., 2009, 38, 1215

2 J H Rayner and H M Powell, J. Chem. Soc., 1952, 319

3 O M Yaghi et al, J. Am. Chem. Soc., 1997, 119, 2861

                  

Source:
http://prospect.rsc.org/blogs/cw/2013/04/24/a-metal-organic-framework-for-progress/