Porous nitrogen-rich g-C₃N₄ nanotubes for efficient photocatalytic CO₂ reduction

The conversion of carbon dioxide (CO₂) into fuels and valuable chemicals using solar energy is a promising method for reducing CO₂ emissions and solving energy supply issues. However, the development of inexpensive, efficient and metal-free materials for photocatalytic CO₂ reduction is challenging. Herein, we report a facile supramolecular self-assembly strategy for the preparation of porous nitrogen-rich graphitic carbon nitride (g-C₃N₄) nanotubes with Lewis basicity and a large surface area, which are beneficial for the adsorption of CO₂ and, consequently, the enhancement of the photocatalytic CO₂ reduction activity. The metal-free porous nitrogen-rich g-C₃N₄ nanotubes catalyst exhibits a superior visible-light-induced CO₂-to-CO conversion rate of 103.6 μmol g⁻¹ h⁻¹, which is 17 and 15 times higher than those of bulk g-C₃N₄ (6.1 μmol g⁻¹ h⁻¹) and P25-TiO₂ (7.1 μmol g⁻¹ h⁻¹), respectively, and exceeds the performance of most metal-free photocatalysts. This work provides new insights into the synthesis of functional groups-modified g-C₃N₄ with a unique structure for effective photocatalytic CO₂ reduction.