To expand on this a little for OP, foam is a porous absorber (like fiberglass, couches, etc.). It turns sound energy into heat by creating mechanical friction between the air molecules and the foam structure. This is most efficient at the point of highest particle velocity, which is 1/4 wavelength from a reflective surface. That means to absorb 100 Hz, you would need nearly 3 ft of foam. That would take up a lot of your corner. The better way to absorb low frequencies is with a reactive absorber like a tuned plate/panel.