First guess is Mulberry, definitely not a paulownia. Are there any other leaves from that tree available? A mulberry should have some on there that have the odd shaped, deep lobed leaves. Second guess is some kind of Basswood, but I've never seen a Basswood leaf that big, but that leaf base doesn't exactly match a Mulberry leaf base. May be a Basswood local to your area I've never seen, I think it is a type of Basswood after consideration.