Intrinsically Microporous Polyimides Derived From Norbornane-2-Spiro-Alpha-Cyclopentanone-Alpha '-Spiro-2 ''-Norbornane-5,5 '', 6,6 ''-Tetracarboxylic Dianhydride

Here, a series of intrinsically microporous polyimides (PIM-PIs) were prepared from norbornane-2-spiro alpha-cyclopentanone-alpha '-spiro-2 '-norbornane-5,5 ',6,6 '-tetracarboxylic dianhydride (CpODA) and archetypal contorted diamines, and their microstructures and gas transport properties were systematically investigated and compared with those of the counterparts derived from 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA). For certain diamines, the surface areas, interchain distances, and fractional free volumes (FFV) of the CpODA-derived PIM-PIs were considerably greater than those of the 6FDA-derived ones, and were in the range of 92-567 m2 g-1, 0.575-0.607 nm, and 0.194-0.246, respectively. Consequently, the CpODA-derived PIM-PIs overall displayed higher gas permeabilities and better gas separation performances compared to the 6FDAderived ones. In particular, CpODA-TBDA2 and CpODA-DAT showed high H2 permeabilities (>600 Barrer) and moderate H2/N2 and H2/CH4 selectivities which approached or even surpassed the corresponding 2008 Robeson upper bounds. The excellent gas separation performance of these CpODA-derived PIM-PIs may be attributed to the contorted and bulky architecture of the CpODA residue, which led to reduced inter- and intramolecular interactions and the formation of ultramicropores of <0.7 nm.