While F2FS (the Flash-Friendly File-System) has been around for a few years, it doesn't yet have any native support by GRUB2 for being able to boot off an F2FS file-system. Fortunately, work is being done in that direction.
F2FS developer Jaegeuk Kim has been working on adding support for his file-system to GRUB2. From here you can get a look at the activity around F2FS for GRUB2.
The most recent version of the patch, which amounts to over 1,000 lines of code, was published last week. Hopefully F2FS support will end up getting merged for GRUB's next release, v2.02.