Fabrication of novel fluorene incorporated conjugated microporous polymer nanotubes for visible-light CO₂ reduction with water vapor

Porous organic polymers have recently attracted great interest as desirable candidates for the solar-driven conversion of CO(2 )molecules to hydrocarbon fuels. However, the interfacial reaction efficiency of polymer photocatalysts is severely suppressed by the limited active sites due to their bulk microstructures. In this work, we report the facile preparation of two nanotube-like photocatalysts on the base of fluorene (Flu) incorporated conjugated microporous polymers by the template-free Sonogashira coupling reaction. The unique nanotube structure endows polymers with surface areas of 450-861 m(2) g(-1), which favors the exposure of active sites and adsorption of CO2 molecules. By replacing the 1,3,5-triethynylbenzene (TEB) core with a 1,3,5-tris(4-ethynylphenyl)benzene (TPB) unit in the polymer backbone, TPB-Flu shows simultaneously reduced optical band gaps, enhanced CO2 uptake and improved charge migration compared with TEB-Flu due to the extended pi-conjugation. As a result, under irradiation with visible light (>420 nm), TPB-Flu nanotubes deliver an impressive CO formation rate of 83.1 mu mol h(-1) g(-1), which is more than 2 fold higher than that of TEB-Flu (40.4 mu mol h(-1) g(-1)). This work paves the way for fabricating novel organic polymer nanotubes in combination with improving the charge migration and CO2 absorption towards the photoconversion of CO2.