disunite vs split up

disunite is not a noun while split up is a noun.

Word	Noun	Adjective	Verb	Adverb
disunite	No	No	Yes	No
split up	Yes	No	Yes	No

As verbs, split up is a hypernym of disunite; that is, split up is a word with a broader meaning than disunite:

Other hypernyms of disunite include break, break up, part, separate, split.

disunite (noun)	split up (noun)
	an increase in the number of outstanding shares of a corporation without changing the shareholders' equity

disunite (verb)	split up (verb)
force, take, or pull apart	become separated into pieces or fragments
part; cease or break association with	get a divorce; formally terminate a marriage
	discontinue an association or relation; go different ways
	separate into parts or portions