If you want a high surface area, liquid cooled material, you might try aluminum and copper foam, open cell. AFAIK, the thermal conductivity and pressure drop is worse than a properly made heatsink.
A similar material can be made from sintering large metal particles, but it's not known for its fluid flow capability; indeed, quite the opposite. Oilite(R) (sintered bronze, oil impregnated) is famous for its ability to retain liquid.
Tim