Crystalline, Porous Figure‐Eight‐Noded Covalent Organic Frameworks

Figure‐eight macrocycles represent a fascinating class of π‐conjugated units characterized by unique aesthetics and non‐contact molecular crossing at the center. Despite progress in synthesis over the past century, research into inorganic, organic, and polymeric figure‐eight materials remains in its infancy. Here we report the first examples of figure‐eight covalent organic frameworks by condensing figure‐eight knots to create extended porous figure‐eight π architectures. A distinct feature is that polymerization interweaves figure‐eight knots into double‐decker layers, which upon supramolecular polymerization organize well‐defined layer frameworks. The figure‐eight frameworks exhibit a bandgap of 2.3 eV and emit bright orange florescence with benchmark quantum yields. Remarkably, the donor‐acceptor figure‐eight skeletons convert the figure‐eight knots into reduction centers and the linkers into oxidation sites upon light irradiation, enable charge transport and accumulation through π columns, while the built‐in hydrophilic micropores allow rapid water and oxygen delivery via capillary effect. With these distinct features, the figure‐eight frameworks function as a photocatalyst to produce hydrogen peroxide at high rate and efficiency with water/saltwater, oxygen/air, and light as sole inputs. This work paves a way to a new class of molecular frameworks, underpinning the study of well‐defined figure‐eight materials to explore unprecedented structures and functions so far we untouched.