Per NASA document:  https://history.nasa.gov/conghand/propelnt.htm

Super high-energy bipropellants_______________________ 300 to 385,   ISP
Fluorine-Hydrogen
Fluorine-Ammonia
Ozone-Hydrogen
Fluorine-Diborane

But Fl is very difficult to handle.  Doing a combustion experiment back in mid 60s, I had a regulator burn up that was apparently not properly passivated that released a whole bottle of flourine to the atmosphere.  No injuries,  luckily.     tom kosvic