national capital vs Ciudad de Mexico

national capital and Ciudad de Mexico both are nouns.

Word	Noun	Adjective	Verb	Adverb
national capital	Yes	No	No	No
Ciudad de Mexico	Yes	No	No	No

national capital (noun)	Ciudad de Mexico (noun)
the capital city of a nation	the capital and largest city of Mexico is a political and cultural and commercial and industrial center; one of the world's largest cities