secede vs split up

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

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

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

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

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

secede (verb)	split up (verb)
withdraw from an organization or communion	become separated into pieces or fragments
	get a divorce; formally terminate a marriage
	discontinue an association or relation; go different ways
	separate into parts or portions