Understanding Adsorption Behavior of Periodic Mesoporous Organosilica Having a Heterogeneous Chemical Environment: Selective Coverage and Interpenetration of Adsorbates inside the Channel Wall

Abstract

Gas adsorption of periodic mesoporous organosilica (PMO) containing bipyridine ligands within the framework (BPy-PMO) has been studied by in situ gas adsorption powder X-ray diffraction (XRD) analysis. Both Ar and CO2 molecules showed strong affinity with organic moiety than silica during monolayer adsorption, even though CO2 is localized more than Ar due to the strong interaction with bipyridine. During multilayer adsorption, adsorbates tend to be located on the silica layers rather than organic and uniformly distributed on the framework surface at the end of this process. The interpenetration of adsorbates within the organic domain of BPy-PMO pore wall enhances rigidity of the framework until capillary condensation, confirmed by decrease of full width at half-maxima (FWHM) of XRD peaks. A molecular simulation study supported the in situ XRD data, and these results provided a full understanding of how the framework environment influences the adsorption behavior of different adsorbates.