所能 is a
所-nominalization:
所 + verb
能 turns 'be able' into 'that which one can do'. Almost always appears as
尽…
所能 (jìn… suǒnéng, do all in one's power) or
各尽所能 (gè jìn suǒnéng, each contributes what they can — the famous Marxist slogan). On its own it's bookish.
