DhaTph Tubes and DhaTph‐Cu Tubes with Hollow Tubular Structure and Their Photocatalytic Reduction of CO2

Abstract Porphyrinic covalent organic frameworks (COFs, specifically DhaTph) in the absence or presence of Cu 2+ in porphyrin centers, were synthesized by a Schiff base condensation reaction of 5,10,15,20‐tetrakis(4‐aminophenyl)‐porphyrin (Tph) and 2,5‐dihydroxyterephthalaldehyde (Dha). Using 2,4,6‐trimethylbenzaldehyde (TBA) as a competition reagent, the hollow DhaTph Tubes and DhaTph‐Cu Tubes were obtained under solvothermal conditions. A detailed mechanism of formation of the tubular microstructure revealed the time‐dependent transformation into the tube via migration of the unstable central part of the initial solid rod. The DhaTph‐Cu Tubes possessed a high photoreduction efficiency of CO 2 and the rate constants of CO and methane production are 15.9 and 13.7 μmol g −1 h −1 in the absence of any cocatalysts, which is about 3 and 7.6 times of DhaTph COF, respectively. The high effective photocatalytic reduction of CO 2 activity of DhaTph‐Cu Tubes is attributed to the high specific surface area, strong absorption of visible light, and the fast separation and transferability of electrons and holes. This work not only provides in‐depth insights into the formation mechanism of the tubular COF but also reveals the relation between the morphology and the photocatalytic property based on COFs.