There is a group project we have and I'm going to refuse to be partners with a good friend of mine.
What about him makes you not want to be partners?
He is a greedy person, he doesn't respect other's contributions and he's a big talker.
Sometimes friendship and work should be separate, it is okay to work apart from your friends. It might help your friendship to not work together if it would lead to fights.
I think he makes a better friend than he does a partner on such projects.
I'm sure your friend will understand as it's unreasonable for friends to expect each other to do everything with each other. Just rationally explain your position on the situation and things will work out just fine.