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

Abstract

Porous organic polymers have recently attracted great interest as desirable candidates for the solar-driven conversion of CO₂ 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 m² 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 π-conjugation. As a result, under irradiation with visible light (>420 nm), TPB-Flu nanotubes deliver an impressive CO formation rate of 83.1 μmol h⁻¹ g⁻¹, which is more than 2 fold higher than that of TEB-Flu (40.4 μmol 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.