Rigid supramolecular structures based on flexible covalent bonds: A fabrication mechanism of porous organic polymers and their CO₂ capture properties

Porous organic polymers (POPs), with dramatic textural properties and versatile uses, were traditionally fabricated by means of rigid covalent bonds or linkages on the basis of judiciously chosen monomers or reaction types. In this study, a new fabrication mechanism of POPs is proposed. For the first time, supramolecular interaction is discovered to be robust to maintain the rigid structures of POPs, even with some flexible or rotatable chemical bonds/linkages, on which a series of successfully fabricated POPs code-named PoBCs are based. Both the first-principle calculations and experimental facts confirm that, owing to π-π stacking and van der Waals’ force, a multi-helix structure can be self-assembled in the course of PoBCs polymer chain growth, which effectively inhibits bending and twisting of the polymer chains and the collapse of intrinsic pore structures. Therefore, the as-synthesized PoBC, especially the PoBC-16, with rigid supramolecular structures possesses satisfactory BET specific surface area (1170 m² g⁻¹) and fully developed porosity (1.08 cm³ g⁻¹), efficiently contributing to both the selective CO₂ capture, of which capacity reaches 67.2 cm³ g⁻¹ at 0 °C and 1 bar, and good reusability, even competitive with many representative benchmark POPs that are based on rigid covalent linkages, for instance, that code-named APOP (BET specific surface area, 490 m² g⁻¹; CO₂ adsorption capacity, 43.6 cm³ g⁻¹ at 0 °C and 1 bar).