Deuterium and tritium are substances with a future – but they are rare. The heavy isotopes of hydrogen not only have numerous applications in science but could also contribute to the energy mix of tomorrow as fuels for nuclear fusion. Deuterium is also contained in some drugs that are currently undergoing regulatory approval in the US. However, the process of filtering deuterium out of the natural isotopic mixture of hydrogen is at present both difficult and expensive. Scientists from the Max Planck Institute for Intelligent Systems, the Max Planck Institute for Solid State Research, the University of Leipzig, Jacobs University Bremen, the University of Augsburg, and Oak Ridge National Laboratory (USA) may be able to remedy this problem. They have presented a metal-organic framework compound that can be used to separate the two isotopes from normal hydrogen more efficiently than previous methods.