Designed synthesis of stable light-emitting two-dimensional sp(2) carbon-conjugated covalent organic frameworks

Covalent organic frameworks enable the topological connection of organic chromophores into pi lattices, making them attractive for creating light-emitting polymers that are pre-designable for both the primary- and high-order structures. However, owing to linkages, covalent organic frameworks are either unstable or poor luminescent, leaving the practical synthesis of stable light-emitting frameworks challenging. Here, we report the designed synthesis of sp(2) carbon-conjugated frameworks that combine stability with light-emitting activity. The C=C linkages topologically connect pyrene knots and arylyenevinylene linkers into two-dimensional all sp(2) carbon lattices that are designed to be pi conjugated along both the x and y directions and develop layer structures, creating exceptionally stable frameworks. The resulting frameworks are capable of tuning band gap and emission by the linkers, are highly luminescent under various conditions and can be exfoliated to produce brilliant nanosheets. These results suggest a platform based on sp(2) carbon frameworks for designing robust photofunctional materials.