A novel 3D sp2 carbon-linked covalent organic framework as a platform for efficient electro-extraction of uranium

Extracting uranium from seawater offers opportunities for sustainable nuclear fuel supply,but the task is quite challenging due to the low uranium concentration(~3 ppb)in seawater.Here,based on the Knoevenagel condensation reaction of aldehyde and acetonitrile groups,a novel stable sp^(2)carbon-linked three-dimensional covalent organic framework(3D COF),TFPM-PDANAO was prepared as a porous platform for uranium extraction from seawater.The TFPM-PDAN-AO designed with regular 3D pore channel of 7.12 A provides a specific channel for uranyl diffusion,which exhibits high selectivity and fast kinetics for uranium adsorption.Meanwhile,the superior stability and optoelectronic properties enable it an excellent porous platform for uranium electroextraction.By applying alternating voltages between-5 and 0 V,uranyl ions can rapidly migrate and enrich into the porous structure of TFPM-PDAN-AO,then inducing the electrodeposition of uranium compounds to form the charge neutral species(Na_(2)O(UO_(3)H_(2)O)x)with an unprecedentedly high adsorption capacity of 4,685 mg g^(-1).This work not only expands the application prospects of functionalized 3D COFs,but also provides a technical support for the electrodeposition adsorption of uranium from seawater.

Alkynyl-Based sp^(2) 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-diyne1,4-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 surfacepositive 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.