Alkynyl-Based sp2 Carbon-Conjugated Covalent Organic Frameworks with Enhanced Uranium Extraction from Seawater by Photoinduced Multiple Effects

Biofouling is a major obstacle to the efficient extraction of uranium from seawater due to the numerous marine microorganisms in the ocean. Herein, we report a novel amidoxime (AO) crystalline covalent organic framework (BD-TN-AO) by Knoevenagel condensation reaction of 2,2',2 ''-(benzene-1,3,5-triyl)triacetonitrile (TN) and 4,4'-(buta-1,3-diynel,4-diyl)dibenzaldehyde (BD) that is highly conjugated and possesses excellent photocatalytic activity. The excellent photocatalytic activity endows the BDTN-AO high anti-biofouling activity by producing biotoxic reactive oxygen species (ROS) and photogenerated electrons to efficiently reduce the loaded U(VI) to insoluble U(IV). Meanwhile, the surface-positive electric field has strong electrostatic attraction to the negative [UO2(CO3)(3)](4-) in seawater, which can significantly enhance the extraction capacity of uranium. Benefiting from these outstanding photoinduced effects of BD-TN-AO, the adsorbent exhibits a high uranium adsorption capacity of 5.9 mg g(-1) under simulated sunlight irradiation in microorganism-containing natural seawater, which is 1.48 times the adsorption capacity in darkness. [GRAPHICS] .

Automated summary

A novel amidoxime (AO) crystalline covalent organic framework (BD-TN-AO) with highly conjugated structure and excellent photocatalytic activity is reported, which exhibits high anti-biofouling activity and efficient extraction of uranium from seawater. The framework's outstanding photoinduced effects lead to a high uranium adsorption capacity under simulated sunlight irradiation in microorganism-containing natural seawater.