Dynamic Studies on Kinetic H2 /D2 Quantum Sieving in a Narrow Pore Metal-Organic Framework Grown on a Sensor Chip.

The separation of deuterium from hydrogen still remains a challenging and industrially relevant task. Compared to traditional cryogenic methods for separation, based on different boiling points of H2 and D2 , the use of ultramicroporous materials offers a more efficient alternative method. Due to their rigid structures, permanently high porosity, tunable pore sizes and adjustable internal surface properties, metal-organic frameworks (MOFs), a class of porous materials built through the coordination between organic linkers and metal ions/clusters, are more suitable for this approach than zeolites or carbon-based materials. Herein, dynamic gas flow studies on H2 /D2 quantum sieving in MFU-4, a metal-organic framework with ultra-narrow pores of 2.5 Å, are presented. A specially designed sensor with a very fast response based on surface acoustic waves is used. On-chip measurements of diffusion rates in the temperature range 27-207 K reveal a quantum sieving effect, with D2 diffusing faster than H2 below 64 K and the opposite selectivity above this temperature. The experimental results obtained are confirmed by molecular dynamic simulation regarding quantum sieving of H2 and D2 on MOFs for which a flexible framework approach was used for the first time.