Ternary boron carbon nitrides hollow nanotubes with tunable p-n homojunction for photo-assisted uranium extraction: A combined batch, EXAFS and DFT calculations

Light-driven catalysis-assisted uranium extraction from seawater opens up a promising avenue to enhance the extraction capacity, kinetics, and selectivity for uranium removal. Herein, we report novel ternary boron carbon nitride hollow nanotubes (BCN-HNTs) with tunable p-n homojunction as metal-free photocatalyst for efficient uranium extraction. Relying on the density functional theory calculations, in conjunction with other spectral analyses, we distinguish the six-membered carbon rings introduced in h-BN to form a tunable p-n homojunction. Accordingly, the BCN-HNTs exhibit a remarkable U(VI) removal rate of > 95% under a wide range of uranium concentrations. By virtue of the X-ray absorption spectroscopy technique, we identify the conversion of 3Oax-U-4Oeq moieties into the 2Oax-U-3Oeq moieties during the transition from dark to light conditions, further verifying the reduction of high-valent uranium. In addition, we find that the introduction of carbon into h-BN lattice enhances the adsorption energy for uranium species, thereby improving the extraction capacity of uranium.