Transforming 2D Imine into 3D Thiazole Covalent Organic Frameworks by Conjugated Connectors: Fully Conjugated Photocatalysts

We developed a robust
three-dimensional (3D) covalent organic framework
(COF), fully conjugated in both the planar (x, y) and interlayer (z) directions, using
a one-pot sulfurization process. We converted the two-dimensional
(2D) imine-linked COF (Py-BDA-COF) to the 3D thiazole-linked COF (3D-Py-BDA-S-COF).
In the interlayer direction (z-axis), the alternating
covalently bound acetylene and ethylene arrangements serve as conjugated
connectors (“pillars”) and create a fully conjugated
and very robust COF in all three dimensions. On top of this, the presence
of the sulfur lone pair electrons in the thiazole rings considerably
enhances the electron delocalization degree of the frameworks. The
3D-Py-BDA-S-COF is successfully evaluated in the photocatalytic reduction
of nitrobenzene.