Observation of the kinetics and measurement of the activation energies for gas diffusion in porous materials requires very fast and sensitive sensors. In this work, thin films of metal-organic frameworks (MOFs) with different pore sizes are grown on a surface acoustic wave (SAW) substrate, resulting in very sensitive and specific sensor systems for the detection of various gases at very short time scales. Using specially designed SAW delay lines for the detection, up to 200-nm-wide cubic MOF crystals were grown directly from a solution on the sensitive sensor chip area. One example, MFU-4, exhibits a smallest pore aperture of 2.5 Å and shows a highly sensitive and specific response to CO, H, He, NH, and HO. It is shown that such a MOF@SAW sensor responds within milliseconds to gas loading and its sensitivity reaches levels as low as 1 ppmv, currently only limited by the gas mixing system. This unique combination of sensitivity and fast response characteristics allows even for real-time investigations of the sorption kinetics during gas uptake and release. As is typical for SAW sensors, the production of the chips is very straightforward and inexpensive and-combined with the unique properties of the MOFs with their tunable pore sizes and adjustable internal surface properties-holds promise for different sensor applications.

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.

A metal–organic framework (MFU‐4) with ultra‐narrow pores has been integrated on a specially designed sensor, with response in the range of milliseconds, and based on surface acoustic waves (SAWs). Selective diffusion of D2 in H2/D2 mixtures below 64 K has been observed due to kinetic quantum‐sieving. More information can be found in the Communication by G. Sastre, A. Wixforth, D. Volkmer, et al. on page 10803.