Reconstruction of biomimetic ionic channels within covalent organic frameworks for ultrafast and selective uranyl capture

The efficient extraction of uranium,as the primary component of nuclear energy,holds significant implications.Drawing inspiration from the charge interaction observed in biological ion channels,we encapsulated negatively charged polystyrene sulfonate(PSS)or sodium polystyrene carboxylate(PVBA)into the nanochannels of amidoxime functionalized covalent organic framework(COF-AO)in-situ to alter the cavity environment of COF-AO.The synthesized COF-AO-PSS and COF-AO-PVBA are used for ultra-fast and highly selective uranium recovery.The negatively charged PSS/PVBA was confined in the COF-AO channel providing the driving force for uranium transport and blocking other ions,thus creating a highly selective“uranium highway”.Additionally,introducing sulfonate groups or carboxyl groups into COF-AO offers supplementary coordination environments and weak interactions with uranium.Due to charge-assisted migration and various interaction mechanisms,both COF-AO-PSS and COF-AO-PVBA exhibit faster adsorption kinetics and higher selectivity compared to COF-AO alone.Their adsorption capacities are 3.8 times and 2.4 times that of COF-AO alone respectively which highlights the necessity for constructing biomimetic ion channels in uranium adsorption processes.This work presents a bionic adsorbent based on covalent organic frameworks(COFs)for the first time,overcoming environmental and equipment limitations associated with traditional photocatalysis and electrocatalysis methods for uranium capture,opening up new avenues for designing multifunctional materials that mimic biological systems.

Redox-active sp^(2)-c connected metal covalent organic frameworks for selective detection and reductive separation of uranium

It is economically desirable to develop a material that can simultaneously detect and recover uranium.Herein,a C=C-bridged two-dimensional metal-covalent organic framework(Cu-BTAN-AO MCOF)was constructed by condensation of metal single crystals with a rigid structure(Cu3(PyCA)3)and cyano monomers(BTAN)via Knoevenagel reaction for simultaneous detection and adsorption of uranium.The amidoxime group within the pore and the presence of unsaturated Cu(I)in the framework facilitate the adsorption of uranyl ions onto the amidoxime group,leading to fluorescence quenching via the photoinduced electron transfer(PET)mechanism,achieving a detection limit of as low as 167 nM uranyl ions.Furthermore,Cu-BTAN-AO demonstrates exceptional efficiency in capturing uranium from wastewater characterized by rapid kinetics and superior selectivity.It is noteworthy that Cu-BTAN-AO is the first example of simultaneous detection,adsorption and chemical reduction of uranium using metal centers and functional groups in MCOF,indicating that Cu-BTAN-AO has great potential for the detection and recovery of uranium-containing wastewater.This design strategy may also be applicable to advancing sensing and energy materials for other important metal ions.

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.