Impact of Dye Encapsulation in ZIF-8 on CO, Water, and Wet CO Sorption.

The fast adsorption kinetics of zeolitic imidazolate frameworks (ZIFs) enable a wide range of sorption applications. The most commonly used framework, ZIF-8, is relatively non-polar. Increasing the polarity of ZIF-8 through the encapsulation of different polar species shows promise for enhancing the sorption performance for pure CO. Recently, the outlook has re-focused on gas mixtures, mostly in the context of post-combustion CO capture from wet flue gasses. While water is known to sometimes have a synergistic effect on CO sorption, we still face the potential problem of preferential water vapor adsorption. Herein, we report the preparation of three ZIF-8/organic dye (OD) composites using Congo red, Xylenol orange, and Bromothymol blue, and their impact on the sorption properties for CO, water, and a model wet CO system at 50% RH. The results show that the preparation of OD composites can be a promising way to optimize adsorbents for single gasses, but further work is needed to find superior ZIF@OD for the selective sorption of CO from wet gas mixtures.