Solid-State Chemical Transformations to Enhance Gas Capture in Benzoxazine-Linked Conjugated Microporous Polymers

We describe the first examples of benzoxazine (BZ)-linked tetraphenylethylene (TPE)- and pyrene (Py)-containing conjugated microporous organic polymers (CMPs)—TPE-TPE-BZ and Py-TPE-BZ, respectively—having high surface areas and pore volumes, prepared through multistep syntheses (Schiff base, reduction, Mannich, and Sonogashira–Hagihara coupling), and their solid-state transformations through ring-opening polymerizations (ROPs) to give BZ linkages have never been reported previously. The chemical structures and, particularly, the presence of BZ units in the TPE-TPE-BZ and Py-TPE-BZ CMPs were confirmed through Fourier transform infrared and solid-state nuclear magnetic resonance spectroscopic analyses. The TEP-TPE-BZ CMP had a high BET specific surface area and a high total pore volume (325 m2 g–1 and 0.69 cm3 g–1, respectively). Because BZ units can undergo ROP through simple thermal treatment without the need for a curing agent or catalyst, the CMPs readily underwent one-step chemical transformations in the solid state to form new CMPs featuring phenolic OH and Mannich bridges as functional groups capable of forming strong intermolecular hydrogen bonds and/or acid/base interactions with molecules of CO2 gas to enhance the gas uptake ability.