Irish capital vs Dublin

Irish capital and Dublin both are nouns.

Word	Noun	Adjective	Verb	Adverb
Irish capital	Yes	No	No	No
Dublin	Yes	No	No	No

As nouns, Irish capital and Dublin are synonyms defined as:

Irish capital and Dublin: capital and largest city and major port of the Irish Republic

Other synonyms of Irish capital include capital of Ireland.

Irish capital (noun)	Dublin (noun)
capital and largest city and major port of the Irish Republic	capital and largest city and major port of the Irish Republic