Conjugated Boron Porous Polymers Having Strong p-pi* Conjugation for Amine Sensing and Absorption

Conjugated porous polymers (CPPs) have drawn significant attention in materials science. We envisioned that simple building blocks may provide a more general platform for constructing functional CPPs. Herein, we report a new synthetic strategy to incorporate a simple boron element building block into CPPs by using efficient boron/tin (B/Sn) exchange reaction, which is distinct from the commonly employed Pd-catalyzed C-C coupling toward CPPs in the literature. More importantly, this synthetic strategy allows us to construct the first example of the CPPs having the nonprotected B-centers and the highest B-content reported to date, which is beneficial for strong Lewis acid-base interactions. The boron (B)-CPPs exhibit the well-defined chemical structures and the microsized porous structures. This synthetic protocol also allows us to access the B-CPPs having the smallest aromatic linker between the B-centers, which can enhance the electronic communications of the adjacent B-centers and increase Lewis acidity of the B-centers. Because of the strong electronic communications of the adjacent B-centers via the p-pi* coupling, the B-CPPs exhibit higher Lewis acidity compared to that of the B-monomer. Combining the high microporosity, the high Lewis acidity, and small steric protection of the B-centers endows these B-CPPs with excellent triethylamine and pyridine sensing and absorptivity properties.