Abstract
Covalent organic frameworks enable the topological connection of organic chromophores into π lattices, making them attractive for creating light-emitting polymers that are predesignable 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 sp2 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 sp2 carbon lattices that are designed to be π 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 sp2 carbon frameworks for designing robust photofunctional materials.
Highlights
Covalent organic frameworks enable the topological connection of organic chromophores into π lattices, making them attractive for creating light-emitting polymers that are predesignable for both the primary- and high-order structures
We explored a tetragonal topology for designing the sp[2] carbon frameworks since it enables π conjugation along both the x and y directions to transmit the π cloud overlap over the 2D skeleton[41]
The C=C linkage is different from the boronate, boroxine, imine, hydrozone, imide, and phenazine bonds since it allows for the formation of fully conjugated systems from all sp[2] carbon
Summary
Covalent organic frameworks enable the topological connection of organic chromophores into π lattices, making them attractive for creating light-emitting polymers that are predesignable for both the primary- and high-order structures. The solid sample of sp2c-COF exhibited an electronic absorption band at 498 nm (Fig. 5a, black curve, Table 1). The absolute fluorescence quantum yields of sp2c-COF, sp2c-COF-2, and sp2cCOF-3 were evaluated to be 15%, 19%, and 12%, respectively (Fig. 5e, Supplementary Table 9).
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