"Nootropics" is too broad, really. There's different ones with different effects. But since you mention coffee, I'd assume you're thinking about Adrafinil/Modafinil, or perhaps racetams.
FDA approval, yeah that would be nice. Unfortunately there's very little public acceptance of the idea that you can take things to improve yourself even if you're already healthy. That being said, L-Theanine and Melatonin are FDA-approved.
Here's a study of Modafinil vs Coffee, for example. It's pretty old and has a low N, but I just mean to show that such research does exist. http://www.gwern.net/docs/modafinil/1993-warot.pdf
FDA approval, yeah that would be nice. Unfortunately there's very little public acceptance of the idea that you can take things to improve yourself even if you're already healthy. That being said, L-Theanine and Melatonin are FDA-approved.