Polymerization of Free-Volume-Promoting Monomers for Methane Absorption

Cationic palladium catalysts containing N-heterocyclic carbene ligands were found to be effective catalysts for the chain-growth polymerization of monomers based on a fused [2.2.1]:[2.2.2] ring system. The shape-persistent monomers prevent dense packing of polymer chains and produce intrinsic microporosity in polymer solids. Gas absorption isotherm measurements reveal that surface areas greater than 1000 m2 g–1 are produced in some materials. High molecular weight materials are produced, and catalyst optimization studies reveal that the steric bulk and electronic nature of the N-heterocyclic carbene ligands play dominant roles in determining the efficiency of the polymerization. The hydrocarbon nature of the microporous polymers enables methane absorption even at high humidity levels, which has anticipated utility in the creation of concentrators for robust point methane sensors.