I figured that he was Emission, but I still think that what he did involves another type of nen...

we've seen an emission boxer back in the greed island arc, and he couldn't send his fists like that (he needed to draw something on the floor), and he actually 'teleported' his fist across the ring.
Leorio punched a guy from a greater distance, and he created a new 'fist', (when the punch hit gin, Leorio had both his hand where they should be). seems fishy.

also, I think that might need to hit an identical object to send the fist (the table, in our case). maybe he can use a knife next time..