Porous, Crystalline, Covalent Organic Frameworks

Covalent organic frameworks (COFs) have been designed and successfully synthesized by condensation reactions of phenyl diboronic acid {C₆H₄[B(OH)₂]₂} and hexahydroxytriphenylene [C₁₈H₆(OH)₆]. Powder x-ray diffraction studies of the highly crystalline products (C₃H₂BO)₆·(C₉H₁₂)₁ (COF-1) and C₉H₄BO₂ (COF-5) revealed expanded porous graphitic layers that are either staggered (COF-1, P6₃/mmc) or eclipsed (COF-5, P6/mmm). Their crystal structures are entirely held by strong bonds between B, C, and O atoms to form rigid porous architectures with pore sizes ranging from 7 to 27 angstroms. COF-1 and COF-5 exhibit high thermal stability (to temperatures up to 500° to 600°C), permanent porosity, and high surface areas (711 and 1590 square meters per gram, respectively).