Enhancement of Chemical Stability and Crystallinity in Porphyrin-Containing Covalent Organic Frameworks by Intramolecular Hydrogen Bonds

摘要

Covalent organic frameworks (COFs) are a new class of porous materials that follow the same rules of reticular chemistry as metal-organic frameworks (MOFs). COFs can be synthesized under relatively mild conditions, using reversible condensation reactions such as boronic acid trimerization, boronate ester formation, the trimerization of nitriles, and the Schiff base reaction. The reversibility of the reactions allows the structural units to self-assemble until they achieve long-range periodicity, which results in the crystallization of COFs. These frameworks exhibit an exceptional high surface area and uniform pore size distributions, and hence can be considered as promising materials for the storage of gases, separation of gas mixtures, catalysis, and charge carrier transport. In general, two classes of porous COFs have been reported: a) chemically stable amorphous porous polymeric structures, often called PAFs/POPs/CTFs with intrinsic porosity and b) porous COFs with high crystallinity but moderate or poor chemical stability.