Prepsitional Phrase

[Unregistered]

I want to be a teacher
"to be" is a prepositional phrase or an infininate

[Soup]

A preposition takes a noun as its object. The word be is not a noun. It's a verb; to be is an infinitive verb.

[svartnik]

I want to be a teacher
"to be" is a prepositional phrase or an infininate

'to' is an infinitive marker and not a preposition, if that is what you mean.