In situ Generation of Reticulate Micropores through Covalent Network/Polymer Nanocomposite Membranes for Reverse-Selective Separation of Carbon Dioxide

We demonstrate the synthesis of a microporous covalent‐network membrane derived from co‐continuous blends of a porogenic urea network and a polyimide (PI). We show that the urea networks in the PI matrix may be thermally rearranged while selectively expelling small molecular fragments, thereby forming a new network bearing reticular microporous molecular pathways. The porous structures enable reverse‐selective gas separation, efficiently blocking carbon dioxide to which most polymeric membranes exhibit selective permeability. The proposed method for fabricating microporous organic membranes with highly tunable porosities using a variety of chemical structures and processing parameters is facile and shows promise for the creation of new membrane‐based molecular‐separation techniques. Selective networking: Reticular microporous channels are generated in situ throughout a urea‐based network film by selective expulsion of molecular fragments during a thermal rearrangement. The nanocomposite membranes exhibited unusual reverse‐selective gas‐transport properties, rejecting carbon dioxide while transporting different gases.