If you are flying on an award ticket in business class but there is a first-class space available on the day of departure with Emirates, you should be able to Upgrade Emirates Flight to that seat for a reasonable number of miles (the same principle applies for upgrading from economy to business, incidentally). If your ticket is issued straight from Emirates, you will typically receive one class upgrade (so partner tickets do not count). When purchasing a ticket through official Emirates channels, you can often upgrade your service level by one service class only.
https://airlinespolicy.com/blo....g/how-to-upgrade-emi