From a flexible hyperbranched polyimide to a microporous polyimide network: Microporous architecture and carbon dioxide adsorption

A dianhydride monomer 2, 5-bis(3, 4-dicarboxyphenoxy)-4′-phenylethynyl biphenyl (PEPHQDA) containing a chain extendable phenylethynyl pendant group has been successfully synthesized via successive nucleophilic substitution , Sonogashira cross-coupling, hydrolysis and dehydration reactions. A flexible microporous polyimide network has been prepared based on the use of triamine (TAPOB), affording hyperbranched polyimide, followed by the curing of phenylethynyl groups to give network structure. Specifically microporous features such as a well-defined surface morphology , microporous structure and nanometer-sized pore channels have been introduced to the flexible polyimide networks through this two-step pathway. This network exhibit a BET surface area (322 m 2  g −1 ) as well as a comparable CO 2 uptake (1.25 mmol g −1 at 273 K and 1 bar) and enthalpy of adsorption (30.3 kJ mol −1 ) to that of other microporous polyimides derived from rigid tridimensional monomers.