Molecular transport in subnanometer pores: zero-point energy, reduced dimensionality and quantum sieving

In microporous materials quantum effects in molecular adsorption and transport become of importance if the difference between pore diameter and the molecular hard core is no longer large compared to the de Broglie wavelength of radial motion. Two aspects are discussed: the freezing of the radial degrees of freedom resulting in a one dimensional gas and the situation where the zero-point energy overcompensates the attraction of the walls, creating an energy barrier at the entrance of the pores. In both cases the material can act as a quantum molecular sieve.