Factors controlling successful formation of mixed-matrix gas separation materials

Prior work has suggested simple guidelines for matching transport characteristics of materials to form high-performance mixed-matrix materials for gas separation. Such materials comprise a dispersion of molecular sieving particles in a properly selected matrix polymer phase. Recent work has shown that these simple criteria are necessary but not sufficient to achieve the desired properties. The analysis presented here shows the need to optimize the transport properties of the interfacial region, i.e., the region between the bulk polymer and dispersed sieve phases. Guided by the need to optimize both the transport properties of the interfacial region and the matrix material selection criteria noted above, a new paradigm is recommended for matrix phase selection. The practicality of the paradigm is validated by the formation of mixed-matrix membranes with an appropriate polymer and sieve. These materials lead to the attractive predicted performances at low loading. For success at higher loading a zeolite "priming" protocol based on polymer-solvent sieve interactions is shown to be necessary. This modified protocol leads to success at intermediate and high dispersed-phase loading.