Polymeric carbon nitride with frustrated Lewis pair sites for enhanced photofixation of nitrogen

Abstract

The bottleneck of photocatalytic nitrogen fixation lies in the rate-limiting reductive activation of robust NN triple bonds with high bond energy. Herein, polymeric carbon nitride with frustrated-Lewis-pairs was constructed by intercalation of electron-deficient boron (B) into metal-free carbon nitride. NH₃-temperature programmed desorption (TPD) and pyridine-adsorption diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results demonstrated that B heteroatoms (Lewis acid) and proximal amino groups (Lewis base) were more likely to form frustrated Lewis pairs, which would capture, activate and reduce N₂ to NH₃ through a “pull–push” effect. Molybdenum-based oxide was further employed as a co-catalyst to improve the charge separation efficiency of site-engineered photocatalysts. The synergistic effect between intercalated B and defective MoO₂ resulted in an 8-fold increased photoactivity of carbon nitride for N₂ fixation. This work provides a new avenue for the rational design and engineering of frustrated Lewis pair sites on polymeric photocatalysts toward efficient N₂ fixation.