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Unless your ticket class permits rescheduling for free (unlikely unless you've booked a more expensive flexible fare class), because these flights will be on two separate tickets, you are owed no protection if the first flight is delayed.
Your options:
You could possibly use a lower fare class on the second ticket, but you will have to pay a fee to reschedule the flight, and if you don't do so prior to the departure of your second flight, you may end up forfeiting the entire fare.