Nanoporous materials, such as metal-organic frameworks (MOFs), enable the separation of various molecular mixtures. Thus, detailed knowledge of multi-component diffusion properties of the guest molecules in the pores is vital. Here, UV/Vis absorption spectroscopy combined with step-by-step-synthesized MOF films with high transparency are used to measure the multi-component dye uptake and diffusion in a straightforward fashion. The time-resolved single-component, binary- and ternary-mixture uptakes of methylene blue (MB), nuclear fast red (NFR) and acid yellow 17 (AY) by MOF films of type HKUST-1 from ethanolic solutions with low dye concentrations were investigated. It was found that the diffusion of MB is approximately one order of magnitude slower than the diffusion of NFR or AY, independent of whether it is a single-component uptake or a mixture uptake.

The Front Cover visualizes the concept based on the high transparency of thin, step‐by‐step‐synthesized metal–organic framework (MOF) films combined with UV/Vis absorption spectroscopy enabling the measurement of multi‐component uptake and diffusion of dye molecules in a straightforward fashion. More information can be found in the Full Paper by M. Saghanejhadtehrani et al. on page 3548 in Issue 24, 2017 (DOI: 10.1002/cphc.201701023).

The front cover artwork is provided by the group of Dr. Lars Heinke. It depicts a schematic of the nanoporous thin film in the center. The three molecules investigated in this study are shown above, with the light coming from the left side, and the experimental results (UV/Vis spectra and diffusion coefficients of the three molecules investigated in this study) on the right side of the MOF film. Read the full text of the article at 10.1002/cphc.201701023.