Change of gas permeation by photoinduced switching of zeolite-azobenzene membranes of type MFI and FAU

FAU membranes of type Na-X and MFI membranes of type silicalite-1 which contain adsorbed azobenzene (AZB), have photoswitchable permeation properties due to the trans-cis photoisomerization of AZB. The change of gas permeation through these host-guest composite membranes depends on the irradiation wavelength, the quality of the membranes and the amount of adsorbed AZB. The permeances of the gases in the trans-form of the zeolite-encapsulated AZB were higher than those in the cis-form. The separation factors of equimolar mixtures of N₂/CO₂ and CH₄/CO₂ fed through the FAU-AZB membrane were higher at trans-switching than at cis-switching. The changes of the permeances of single gases and of the separation factors of equimolar gas mixtures by photoinduced trans-cis switching were found to be reversible over numerous switching cycles. The experimental results are in agreement with predictions made by Monte Carlo simulations for passing of permeant gases through these host-guest systems with the zeolitehosted AZB in the trans- and in the cis-configuration.