The science behind this weapon is a crystal that absorbs Oxygen (See Science Daily, IFLScience or PopSci) for release later. The fact “A bucket full (10 litres) of the material is enough to suck up all the oxygen in a room.” is not much use on the surface of a planet, but in confined spaces like airlocks, or small rooms where it will take some find for the oxygen (O2) to return to breathable levels it has some potential. The other important thing about this substance it that it will release the O2 when there is a lack of oxygen or when heated.
One option is for the long term storage of O2 on spaceships, or for oxygen scrubbers that strip out the oxygen of the carbon dioxide (CO2.) to enable better life support systems. With heat releasing the oxygen when needed. A similar system could be create for deep sea exploration to remove the O2 from the water for use in the submarine.
Another option is a 2 kg aerosol canister can release this in a powdered form as a knock-out weapon for boarding actions on spaceships. Although the clean up would be difficult with the substance getting everywhere. A better idea maybe a trap, where the canister is opened the characters enter the room.
This will result in Hypoxia to the body and brain (Cerebral hypoxia). According to Wikipedia the list of symptoms for hypoxic hypoxia are: Cyanosis, Headache, Decreased reaction time, Impaired judgment time, Euphoria, Visual impairment, Drowsiness, Lightheaded or dizzy sensation, Tingling in fingers and toes, & Numbness. All of which can be experienced by mountain climbers and other people who are about 10,000 feet.