Is it possible to contain dark matter in a vacuum?

Dark matter is speculated, not observed. To my knowledge, its hypothetical existence was invented to explain peculiar cosmic phenomena (eg missing portion of gravitation), like the aether of old which einstein eliminated in his theories of relativity. By definition, it does not interact with nor emit electromagnetic energy, so it's about as scientific as "will of the universe".

If you meant antimatter, then yes; it's necessary since they are attracted to their counterparts, and upon collision would result in mutual annihilation + energy burst. However, in order to be able to study these minuscule traces of antimatter in say a lab environment, they use powerful electric & magnetic fields to negate the attraction effect in a smaller locality of vacuum.