split up vs come apart

split up is a noun but come apart is not a noun.

Word	Noun	Adjective	Verb	Adverb
split up	Yes	No	Yes	No
come apart	No	No	Yes	No

As verbs, split up and come apart are synonyms defined as:

Other synonyms of split up include break, fall apart, separate.

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

split up (verb)	come apart (verb)
become separated into pieces or fragments	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