without a workaround, no. If it’s a 3D layer, and camera DOF is on, it gets what the camera is set to.
workarounds:
render without object you want in focus, then
render again with object solo’d and cam DOF turned off. (comp’ing and mattes might be needed to pull off, dunno your scene)
make your layer you want sharp, not a 3D layer and “fake” whatever about it would happen in 3D space. again, don’t know your scene, might work, might not.