One-Dimensional and Pseudo-Two-Dimensional Helicene Covalent Organic Frameworks

Here we report the synthesis of one-dimensional (1D) covalent organic frameworks constructed from spatially folded helicene units that are topologically forbidden in a conventional topology design. A carbazole-fused helicene adopts a V-shaped geometry with two reactive sites oriented at 104° and vertically separated by 4.4 Å, a configuration incompatible with the allowed 1D framework growth. Unexpectedly, condensation with tetrasubstituted <i>C</i>₂-symmetric π knots produces unprecedented 2-fold-interpenetrated 1D belt architectures, in which <i>P</i>- and <i>M</i>-helicene isomers are chiral sorted along opposite edges. These belts further assemble into pseudo-two-dimensional (2D) frameworks through homochiral <i>P</i>-on-<i>P</i> and <i>M</i>-on-<i>M</i> stacking column arrays that facilitate charge transport. Visible light irradiation converts the frameworks into photocatalytic skeletons, where the knots reduce oxygen, the helicene units oxidize water, and the micropores deliver water and oxygen, producing hydrogen peroxide directly from oxygen and water without the need of metal cocatalysts and sacrificial agents. These findings open a way to unconventional 1D and pseudo-2D frameworks and photocatalysts.