A passive heat sink for cooling an electronic component such as a high-performance processor. The heat sink includes a shell with a surface that is positionable adjacent a heat generating surface of the electronic component. The shell includes a heat exchanger portion with cooling fins extending outward and positioned in a fan-provided airflow. A generator compartment is provided within the shell with a generator vessel for containing an absorbent, and the generator compartment is maintained at a pressure lower than ambient. The generator compartment conducts heat away from the electronic component to the absorbent in the generator vessel. An absorber compartment, at a pressure lower than the generator compartment, is provided within the shell above the generator compartment, and, in use, an absorption refrigeration cycle contained within the shell is activated by heat from the electronic component. A bubble pump moves absorbent from the generator compartment to the absorber compartment.