Microtubular Self‐Assembly of Covalent Organic Frameworks

Despite significant progress in the synthesis of covalent organic frameworks (COFs), reports on the precise construction of template‐free nano‐ and microstructures of such materials have been rare. In the quest for dye‐containing porous materials, a novel conjugated framework DPP‐TAPP‐COF with an enhanced absorption capability up to λ=800 nm has been synthesized by utilizing reversible imine condensations between 5,10,15,20‐tetrakis(4‐aminophenyl)porphyrin ( TAPP ) and a diketopyrrolopyrrole ( DPP ) dialdehyde derivative. Surprisingly, the obtained COF exhibited spontaneous aggregation into hollow microtubular assemblies with outer and inner tube diameters of around 300 and 90 nm, respectively. A detailed mechanistic investigation revealed the time‐dependent transformation of initial sheet‐like agglomerates into the tubular microstructures.