Quantum Molecular Sieving in Carbons

Introduction The molecular sieving of isotopes has long been considered impossible, as they are of essentially identical size and shape. However, for light isotopes such as H2 and D2, quantum effects can lead to sufficiently large differences in de Broglie wavelengths at cryogenic conditions to make their molecular sieving possible in nanoporous materials having pores of molecular dimension. Whilst most of the attention [1,2] has focused on adsorption equilibrium, our recent simulations have shown remarkable counterintuitive effects, with the heavier deuterium diffusing faster than hydrogen at sufficiently low temperatures in nanoporous materials [3-5]. Here, we report the first microscopic experimental verification of this prediction, using quasi-elastic neutron scattering, along with extensive simulations of D2/H2 quantum separation in carbons. The results suggest suitable structures for facilitating the quantum effect, opening the door for carbon-based quantum effect-mediated kinetic separation of light isotopes.