[tobias2014]

I was interested and looked at the actual patent: https://patents.justia.com/patent/4348422 (there seem to be multiple patent documents, but this one adds some explanation), and he writes "I have now surprisingly discovered".

https://tastydecafs.com/blogs/learn-about-decaf/co2-decaf further explains "The story of C02 decaffeination goes back to 1967. It was then when a chemist at Max Planck Institute named Kurt Zosel stumbled upon an interesting discovery. Zosel, like many other chemists, was using high-pressure C02 to remove individual substances from other mixtures."

It must have something to do with caffeine being an alkaloid, while coffee overall is acidic. So I suspect that this pressurized CO2 is able to dominantly remove such alkaloids... I leave the details to a chemist :)

[RamblingCTO]

To add some clarification: decaffeination is as old as 1903 (also Germany: https://en.wikipedia.org/wiki/Decaffeination)

[DonaldPShimoda]

But the parent comment is about CO2 decaffeination specifically, not decaffeination in general.