Flexible Porous Polynorbornenes with Alkene Linkage for Decolorizing the Highly Reactive Triisocyanate in Ethyl Acetate

Porous materials with structural flexibility have gained significant attention in recent years. However, the flexible porous organic polymers (POPs) have been rarely reported due to the lack of efficient synthesis. Herein, a rigid-flexible transformation strategy based on ring-opening metathesis polymerization (ROMP) was employed to synthesize the flexible polynorbornenes with isolated alkene linkage (BIT-POPs). The flexibility of as-prepared BIT-POPs was investigated by low-field NMR based on the transverse relaxation time (T2) of organic solvents. BIT-POP-10 can be used to decolor triisocyanate called Desmodur RE (DRE), with the decolorization efficiency of up to 99.5% and separation efficiency of up to 100%. Solid-state NMR (ssNMR) along with X-ray photoelectron spectroscopy revealed that the excellent performance of BIT-POP-10 for purification of DRE was attributed to the formation of intermolecular hydrogen bonding between the carbonyl groups of imides and amino groups of Basic Red 9 (BR-9).