I don't know if they've studied coconut oil at all, but I know most commercial lubes have been found to inhibit sperm, either by stopping it or slowing it down. OTOH, who wants to skip the lube if you're dry? Apparently saliva doesn't help either.
We didn't have any trouble TTC the first time around, but I was very dry after a late m/c (at 19 weeks, induction and D&C so more medically involved than most m/c) so after a few months with no luck, we tried Pre-seed. It's designed to mesh with the consistency of fertile cervical fluid. I don't know if it really does, but we did get pg the first time we used it. In terms of feel it doesn't feel as good as a lube, and you have to use an applicator to get it close to your cervix (we tried using it right out of the tube like a regular lubricator and it just didn't cut it). It's also worth noting that it's expensive, hard to find (although you can purchase it online), and doesn't have a super-long shelf life.
I'd link to the studies I'd found, but the most detailed study I came across was on the Pre-seed website--hardly unbiased information.
However, I'd still recommend it, since the bottom line is that it worked for us.
If you prefer to go natural, I've seen raw egg white recommended, but the ick factor (and the salmonella issue) was too big for me to overcome.