Rapid Quantification of Mass Transfer Barriers in Metal–Organic Framework Crystals

Although mass transfer of molecules in and out of porous materials such as zeolites and metal–organic frameworks impacts many applications, the fast and reproducible measurement of intracrystalline diffusion and surface permeability in porous materials remains challenging. Here, we demonstrate how a commercially available volumetric adsorption instrument can be used to reliably obtain guest mass transfer rates in nanoporous materials. The measurements are rapid and allow for the determination of intracrystalline diffusion coefficients and surface permeabilities in multiple adsorbents simultaneously, as well as the parallel collection of their adsorptive properties. In addition to describing the experimental procedures in detail, we provide a user-friendly code to facilitate the data analysis to obtain the transport parameters from adsorption uptake experiments and to determine the rate limiting process. Using the metal–organic frameworks MOF-808, NU-1000, and UiO-66, we illustrate the reproducibility of this technique for different sample masses across a variety of pressures. Wider adoption of this method─using commonly available equipment─should contribute to a better understanding of mass transport in nanoporous materials.