Stepwise observation and quantification and mixed matrix membrane separation of CO(2) within a hydroxy-decorated porous host

The identification of preferred binding domains within a host structure provides important insights into the function of materials. State-of-the-art reports mostly focus on crystallographic studies of empty and single component guest-loaded host structures to determine the location of guests. However, measurements of material properties (e.g., adsorption and breakthrough of substrates) are usually performed for a wide range of pressure (guest coverage) and/or using multi-component gas mixtures. Here we report the development of a multifunctional gas dosing system for use in X-ray powder diffraction studies on Beamline I11 at Diamond Light Source. This facility is fully automated and enables in situ crystallographic studies of host structures under (i) unlimited target gas loadings and (ii) loading of multi-component gas mixtures. A proof-of-concept study was conducted on a hydroxyl-decorated porous material MFM-300(V(III)) under (i) five different CO(2) pressures covering the isotherm range and (ii) the loading of equimolar mixtures of CO(2)/N(2). The study has successfully captured the structural dynamics underpinning CO(2) uptake as a function of surface coverage. Moreover, MFM-300(V(III)) was incorporated in a mixed matrix membrane (MMM) with PIM-1 in order to evaluate the CO(2)/N(2) separation potential of this material. Gas permeation measurements on the MMM show a great improvement over the bare PIM-1 polymer for CO(2)/N(2) separation based on the ideal selectivity.