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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 sp2 carbon-linked three-dimensional covalent organic framework (3D COF), TFPM-PDAN-AO was prepared as a porous platform for uranium extraction from seawater. The TFPM-PDAN-AO designed with regular 3D pore channel of 7.12 Å 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 (Na2O(UO3H2O)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. [ABSTRACT FROM AUTHOR]

The gas-sensing performance of PbSnS2 monolayer to sulfur hexafluoride (SF6) decompositions (SO2, H2S, HF, SOF2, and SO2F2) has been systematically studied by density functional theory and nonequilibrium Green’s function calculations. The most stable adsorption configurations, adsorption energies, charge transfer, electron localization function (ELF), density of states (DOS), and ${I}$ – ${V}$ curves of gas molecules on PbSnS2 are calculated and discussed. SO2 exhibits the largest adsorption energy of −0.74 eV with the charge transfer of −0.39 e and HF possesses the biggest charge transfer of −0.66 e with the adsorption energy of −0.46 eV. The results of ELF and DOS show that the interaction between SO2 and PbSnS2 may be stronger than those of other gases. Moreover, ${I}$ – ${V}$ curves show that the responses of PbSnS2 to SO2 is up to 65.5% at the bias of 2.2 V. Therefore, PbSnS2 monolayer may be a qualified material for detecting SF6 decompositions. [ABSTRACT FROM AUTHOR]

Facing the complex coexistence of various metal ions in wastewater and mineral resources, metal–organic frameworks (MOFs) with diverse functionalities and tunable pores are poised to serve as distinctive solutions for efficiently recognizing and selectively separating radioactive thorium (Th(IV)). Herein, a fluorescent MOF (DBT‐DHTA‐Cd) with unique thorium nanocavity traps is rationally designed by using two rigid ligands, including azole and hydroxyl groups, respectively. Notably, the synergistic effect of the appropriate pore size and dense hydroxyl···N nanocavity traps in DBT‐DHTA‐Cd results in selective capture of Th(IV), arising from the high charge density of nano‐trap and extremely low binding energy (Eads = −602.7 KJ mol−1). The fast adsorption kinetics (30 min) and rapid fluorescence response (1 min) of DBT‐DHTA‐Cd toward Th(IV) are attributed to the stronger electron holding capacity of the d and f orbitals belonged to Th(IV), making it more prone to accepting electrons transferred from the N/O active sites in the nano‐trap. As a verification test, tailing breakthrough experiments confirm that DBT‐DHTA‐Cd can efficiently purify Th(IV) from monazite mining solid waste in one step. This work provides profound insights into relationship between structure and property of MOFs and has valuable guidance for designing materials in the radioactive purification field. [ABSTRACT FROM AUTHOR]

Untreated radioactive iodine (129I and 131I) released from nuclear power plants poses a significant threat to humans and the environment, so the development of materials to capture iodine from water media and steam is critical. Here, we report a charge transfer complex (TCNQ-MA CTC) with abundant nitrogen atoms and π-conjugated system for adsorption of I 2 vapor and I 3 - from aqueous solutions. Due to the synergistic binding mechanism of benzene/triazine rings and N-containing groups with iodine, special I-π and charge transfer interaction can be formed between the guest and the host, and thus efficient removal of I 2 and I 3 - can be realized by TCNQ-MA CTC with the adsorption capacity up to 2.42 g/g and 800 mg/g, respectively. TCNQ-MA CTC can capture 92% of I 3 - within 2.5 min, showing extremely fast kinetics, excellent selectivity and high affinity (K d = 5.68 × 106 mL/g). Finally, the TCNQ-MA CTC was successfully applied in the removal of iodine from seawater with the efficiency of 93.71%. This work provides new insights in the construction of charge transfer complexes and lays the foundation for its environmental applications. [Display omitted] • A π-conjugated and hydrogen-bonded charge transfer complex (TCNQ-MA CTC) was prepared. • The TCNQ-MA CTC has a high affinity for iodine due to the aboundant binding sites. • The TCNQ-MA CTC can adsorb I 2 and I 3 - with large capacity and good selectivity. • The TCNQ-MA CTC shows fast adsorption kinetics with the removal rate of 92% in 2.5 min [ABSTRACT FROM AUTHOR]

• TFHH-POM was developed by using amino-modified polyoxometalates embedded in covalent organic framework pores. • The covalent bond connection between TFHH and POM improves the stability of POM. • Covalent bonding and internal confined improve the mass transfer from TFHH to POM. • TFHH-POM exhibits a notably elevated photoreduction capacity of U(VI). To achieve sustainable nuclear energy and environmental protection, capturing uranium from mining wastewater is imperative. Herein, as an extraction composite of U(VI), TFHH-POM was developed by using a highly conjugated polyaromatic ether-based covalent organic framework (TFHH) as the carrier with amino-modified polyoxometalates (POM) embedded in its pores through amide bonds. The highly conjugated structure of TFHH facilitates charge transport, and in combination with the charge density contrast between POM and TFHH, along with the constraining effect of POM within TFHH channels, jointly enhances charge separation efficiency. As a result, the photoreduction efficiency of U(VI) is substantially increased. Simultaneously, the oxygen-containing groups in POM and carboxyl groups in TFHH could selectively adsorb U(VI), while Mo(V) in POM effectively reduces U(VI) to U(IV), synergistically promoting U(VI) capture. Hence, TFHH-POM exhibits remarkable U(VI) extraction efficiency through enhanced mass transfer, improved diffusion, and introduced chemical reduction. The U(VI) extraction capacity of TFHH-POM reaches 489.2 mg/g, surpassing those of POM and TFHH by 3.2 and 1.6 times, respectively. The reduced U(IV) remains stable after 30 days of storage with no reoxidation observed. Moreover, TFHH-POM demonstrates selective U(VI) capture from mining wastewater, highlighting its vast potential for environmentally sustainable uranium mining. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bi-functional COF based heterostructure (NH 2 -Ti 3 C 2 T x @COF) was developed in situ. • The Schottky interface realizes efficient carrier separation and solar utilization. • NH 2 -Ti 3 C 2 T x @COF has excellent photocatalytic activity without sacrificial agents. • NH 2 -Ti 3 C 2 T x @COF exhibits multiple-in-one advantage for photoreduction U(VI). Reduction of soluble U(VI) to insoluble U(IV) is considered as a promising strategy to avoid uranium contamination. Herein, a bi-functional covalent organic framework based heterojunction (NH 2 -Ti 3 C 2 T x @COF) was constructed on the amino-modified Ti 3 C 2 T x MXene for efficient photoreduction U(VI) without additional sacrificial agents. Schottky interface with electronic unidirectional channel is established by the formation of local electrophilic/nucleophilic region due to the introduction of reductive COF with alkynyl group, resulting in efficient photogenerated carrier separation and solar energy utilization. More importantly, NH 2 -Ti 3 C 2 T x with negative charge served as electron collector and transfer channel can effectively surmount the low photocatalytic activity caused by high polarization of imine-linked COFs. Thus, the tailored-made design of NH 2 -Ti 3 C 2 T x @COF exhibits excellent photocatalytic activity, fast reaction kinetics (removal of 97.8 % in 60 min) and high adsorptive capability (1557.2 mg/g) under the light condition. This multiple-in-one advantage makes well-designed NH 2 -Ti 3 C 2 T x @COF as a promising capture platform. This work will provide some new insight and inspiration to COF based heterojunctions for enhancing U(VI) capture. [ABSTRACT FROM AUTHOR]

[Display omitted] • A metal coordination polymer Zn-Vlm 6 enriched with imidazole was synthesized to remove iodine. • The imidazole group and the free counter anion NO 3 – in Zn-Vlm 6 play a vital role in the I 2 /I 3 − adsorption. • In the presence of excess competing anions, Zn-Vlm 6 exhibited excellent selective removal of I 3 −. • Zn-Vlm 6 could remove I 3 − in the actual aqueous environment (e.g., lake water, seawater). Rationally designing a new adsorbent with highly selective and high adsorption capacity for removing I 3 − from water is still a significant challenge. Herein, we report an imidazole group-rich coordination polymer (CP) named Zn-Vlm 6 , which was constructed by the reaction of the 1-vinylimidazole (Vlm) and Zn2+ ions. Zn-Vlm 6 showed excellent thermal and chemical stability (1 M HCl and 0.1 M NaOH). The abundance of positively charged imidazole groups and the free anti-anion NO 3 − in the backbone of Zn-Vlm 6 results in strong electrostatic interactions and ion exchange between the material and the guest, in return, a high adsorption capacity for I 3 − (1680.7 mg g−1). In addition, the kinetics of I 3 − adsorption on Zn-Vlm 6 followed the pseudo-second-order kinetic model and reached adsorption equilibrium within 3 min. More importantly, Zn-Vlm 6 can selectively capture I 3 − in the presence of competing anions and selectively remove high up to 96.4% of I 3 − from different environments (e.g., lake water, seawater). Moreover, Zn-Vlm 6 can also adsorb gaseous iodine up to 2470 mg g−1. This study shows that Zn-Vlm 6 has promising applications for removing iodine in the gaseous state and from different aqueous phases. [ABSTRACT FROM AUTHOR]

[Display omitted] • A 3D cationic covalent organic framework (TFAM-BDNP) was synthesized via Zincke reaction. • TFAM-BDNP exhibits high adsorption capacity and extremely fast exchange kinetic for ReO 4 −. • TFAM-BDNP demonstrates remarkable selectivity for ReO 4 −. • TFAM-BDNP has outstanding removal efficiency of ReO 4 − from simulated Hanford flow sample. Due to the long half-life and high environmental mobility, the selective and efficient capture of TcO 4 − from nuclear effluents is very important, but it is still very challenging. Herein, we design and synthesize a novel three-dimensional (3D) cationic covalent organic framework (TFAM-BDNP) via Zincke reaction for selective capture of TcO 4 −/ReO 4 −. TFAM-BDNP exhibits high adsorption capacity (998 mg g−1) and extremely fast exchange kinetic (60 s) for ReO 4 − (the non-radioactive alternative to TcO 4 −), attributing to the open 3D hydrophobic channels, abundant active sites, and high chemical stability. More importantly, TFAM-BDNP shows good adsorption performance for ReO 4 − in the presence of significant excess competing anions with a wide pH value range of 2 to 12. Under complex simulated Hanford flow sample, TFAM-BDNP has outstanding removal efficiency of ReO 4 −. The adsorption mechanism of ReO 4 − is mainly caused by anion exchange process. This study provides a novel adsorbent for efficient capture of TcO 4 −/ReO 4 − in complex environmental systems and exploits an effective strategy for broadening the types of 3D COFs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Indium-based MOF is synthesized for the efficient removal of iodine from both the vapor and aqueous. • In-MOF exhibits high hydrostability even in seawater for 30 days. • In-MOF shows high selectivity and adsorption capacity for I 3 -. • In-MOF shows high-efficiency removal for iodine in seawater. The highly efficient removal of radioactive iodine from nuclear accident-polluted seawater is of great significance for the purpose of environmental protection. Herein, we report an indium-based metal–organic framework, named In-MOF, for highly efficient removing iodine from seawater. In-MOF is constructed by In3+ ions coordinated with tris (4-(1H-imidazol-1-yl) phenyl) amine and exhibits high chemical stability even under seawater for 30 days. Due to the flexible one-dimensional linear structure and high-density charged imidazolium groups, In-MOF possesses a high adsorption capacity (1138 mg/g) for iodine in water. Furthermore, it exhibits high selectivity in the presence of competitive ions, due to forming the unique I-π interactions between iodine and the In-MOF. Notably, these excellent adsorption features endowed In-MOF successfully remove iodine from seawater with a high removal rate of 93.86%. These results are of fundamental importance to understanding iodine uptake and designing materials with high adsorption capacity. [ABSTRACT FROM AUTHOR]

Effective and selective removal of 99TcO 4 -, one of the most nuisance radionuclides in nuclear waste, is highly desirable but remains a significant challenge. Herein, two isostructural MOFs, NCU-3-X (X = Cl, Br) were constructed by ZnX 2 coordinated to nitrogen-containing neutral ligand tri(4-(1H-imidazole-1-l) phenyl) amine for efficient adsorption ReO 4 -/TcO 4 -. Owning to the twofold interpenetrating structure, both of them exhibit strong alkaline resistance. Consequently, NCU-3-Br exhibited superior adsorption performances with a maximum capacity as high as 483 mg/g, which is 2.23 times larger than that of NCU-3-Cl. The primary reasons accounting for the enhanced adsorption performances of NCU-3-Br are that compared to chlorine atoms, the smaller electronegativity of bromine atoms as halogen bonds donor can facilitate the formation of σ-holes, enhance positively charged skeleton, and reduce the adsorption energy associated with ReO 4 -/TcO 4 -. In addition, the one-dimensional hydrophobic channels in the NCU-3-Br framework enable NCU-3-Br to have highly selective toward ReO 4 -, which has a low relative charge density against interfering ions. The SRS simulation removal experiment further confirmed the excellent adsorption capacity of NCU-3-Br to ReO 4 -/TcO 4 -. This work illustrated that the halogenated new strategy incorporated different halogen atoms into MOF skeletons can dramatically modulate the adsorption performances for ReO 4 -/TcO 4 -. [Display omitted] • Two halogens isostructural MOFs were designed and synthesized for efficient removal of TcO 4 -/ReO 4 -. • The high alkaline resistance was due to the twofold interpenetrating structure of NCU-3-X. • Halogenation in MOFs plays a critical role in modulating the adsorption capacity for ReO 4 -. • NCU-3-Br showed high-efficiency removal for ReO 4 -/TcO 4 - in simulated wastes. [ABSTRACT FROM AUTHOR]

It has been considered challenging to develop ideal adsorbents for efficient and lower adsorption time uranium extraction, especially 3D covalent organic frameworks with interpenetrating topologies and tunable porous structures. Here, a "soft" three-dimensional (3D) covalent organic framework (TAM-DHBD) with a fivefold interpenetrating structure is prepared as a novel porous platform for the efficient extraction of radioactive uranium. The resultant TAM-DHBD appears exceptional crystallinity, prominent porosity and excellent chemical stability. Based on the strong mutual coordination between phenolic-hydroxyl/imine-N on the main chain and uranium, TAM-DHBD can effectively avert the competition of other ions, showing high selectivity for uranium extraction. Impressively, the 3D ultra-hydrophilic transport channels and multi-directional uniform pore structure of TAM-DHBD lay the foundation for the ultra-high-speed diffusion of uranium (the adsorption equilibrium can be reached within 60 min under a high-concentration environment). Furthermore, the utilization of lightweight structure not only increases the adsorption site density, but renders the adsorption process flexible, achieving a breakthrough adsorption capacity of 1263.8 mg g-1. This work not only highlights new opportunities for designing microporous 3D COFs, but paves the way for the practical application of 3D COFs for uranium adsorption. [Display omitted] • A three-dimensional covalent organic framework (TAM-DHBD) is prepared for extraction of uranium. • TAM-DHBD can effectively avoid the competition of other ions, showing high selectivity to uranium. • TAM-DHBD possesses superhydrophilic transport channels and multidirectional uniform pore structure. • The lightweight structure increases adsorption site density and makes adsorption process flexible. • TAM-DHBD achieved a breakthrough adsorption capacity of 1263.8 mg g-1. [ABSTRACT FROM AUTHOR]

In this paper, a novel graphene oxide (GO)-based cadmium-imprinted polymer (Cd(II)-IIP) was firstly prepared via surface ion imprinted technology (SIIT) and reversible addition-fragmentation chain transfer polymerization (RAFT) in microemulsion system. In the polymerization methodology, the RAFT technology was applied to controlling the morphology and functionality of the imprinted polymer. The polymerization was conducted in the microemulsion system to keep stable polymerization process. The obtained Cd(II)-IIP was characterized by FT-IR, SEM, AFM, XRD and TGA, proving to be with uniform morphology, as well as favorable thermal stability. The adsorption properties and selectivity of Cd(II)-IIP towards Cd(II) were investigated, indicating high adsorption capacity, fast mass transfer rate and distinct selectivity upon exposure to complex contaminants. In addition, thermodynamic parameters and adsorption–desorption cycles were all studied to comprehensively assess the adsorbent performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • MI-TBPAFs acted as a palladium capture platform through three synergistic mechanisms. • The MI-TBPAFs with numerous tailored binding sites exhibited extraordinary selective affinity with palladium. • Pd2+ was reduced into Pd0 by MI-TBPAFs via photocatalytic and chemical reduction effects. • MI-TBPAF-3 showed ultra-high adsorption capacity for palladium (435.4 mg/g) under simulated sunlight radiation. Herein, molecular imprinting technology (MIT) was introduced into construction of molecularly imprinted triazine-based porous aromatic frameworks (MI-TBPAFs) via Heck-coupling reaction for palladium extracting from wastewater. According to the decorating Pd-vinylpyridine complex (Pd@Vpy), MI-TBPAFs were given considerable tailor-made binding sites with strong affinities for palladium, which captured palladium from various metal ions precisely. The adsorption experiments showed that the extraction capacity of MI-TBPAF-3 was improved by 59.0% (435.4 mg/g) under simulated sunlight radiation. Mechanism analysis proved that Pd2+ was reduced into Pd0 by MI-TBPAF-3 via photocatalytic and chemical reduction effects originating from triazine base and pyridine nitrogen atoms in the extended π-conjugated framework respectively, thereby greatly increasing adsorption capacity by the sorption-reduction strategy. Organically combining the advantages of MIT, photocatalytic reduction and chemical reduction, three synergistic mechanisms, not only provides a new strategy for highly efficient palladium extraction, but also inspires new insights for precious metal recovery. [ABSTRACT FROM AUTHOR]

[Display omitted] • The synthesis of bi-function natural polymers is simple without expensive catalytic agents. • Bi-function natural polymers show superior selectivity and fast adsorption kinetics for recovery of gold. • Bi-function natural polymers act as the adsorbents for gold recovery through the synergistic mechanisms of adsorption and reduction. • The PDA-TFN-A exhibits outstanding Au(III) adsorption capacity up to 2771.8 mg/g at pH 2.0. Designing and synthesizing cost-effective and biodegradable adsorbents for recovering gold from electronic acidic waste have immense sustainable development significance. Herein, three natural macromolecules (polydopamine, chitosan and cellulose) as raw materials were selected to be chemically crosslinked with tetrafluoroterephthalonitrile (TFN) through aromatic nucleophilic reaction, respectively. Then cyano groups of the cross-linked products were converted into amides under alkaline conditions then gained PDA-TFN-A, Chitosan-TFN-A and Cellulose-TFN-A for specifically binding gold. The gold adsorption capacities were 2771.8, 2680.0 and 1992.0 mg g−1 for PDA-TFN-A, Chitosan-TFN-A and Cellulose-TFN-A, respectively. Moreover, various physicochemical and spectroscopic studies provided insight into the binding process, confirming the highly efficient adsorption and in-situ reduction of gold of bifunctional natural polymers based on the interaction of amide functional groups with Au and chloro gold complexes. In addition, the comparative analysis proved the optimum behavior of bi-functional natural polymer PDA-TFN-A with high capacity, selectivity, stability, and fast adsorption kinetics (15 min) for adsorption of gold. This work delineated a promising strategy for the application of eco-friendly natural polymers to solve environmental problems. [ABSTRACT FROM AUTHOR]

We report the first example of covalent organic framework (DHBD-TMT) linked by unsubstituted olefin-linkages for selective loading, chemical reduction and photocatalytic reduction of uranium. The unique structures of DHBD-TMT possess all the characteristics to be well suited as a capture platform for selective ligand complexation, efficient chemical reduction and photocatalytic reduction of uranium, thus exhibiting a groundbreaking uranium capture capacity (2640.8 mg g-1). [Display omitted] • Covalent organic framework (DHBD-TMT) as a uranium adsorbent through three synergistic mechanisms. • This is the first example of covalent organic framework for selective adsorption, chemical reduction and photocatalytic reduction of uranium. • DHBD-TMT is very suitable as a capture platform for selective ligand complexation, efficient chemical reduction and photocatalytic reduction of uranium. • DHBD-TMT exhibited a groundbreaking uranium capture capacity. Herein, we report the first example of covalent organic framework (DHBD-TMT) linked by unsubstituted olefin-linkages for selective loading, chemical reduction and photocatalytic reduction of uranium. The unique structures of DHBD-TMT possess all the characteristics to be well suited as a capture platform for selective ligand complexation, efficient chemical reduction and photocatalytic reduction of uranium, thus exhibiting a groundbreaking uranium capture capacity (2640.8 mg g-1). In the dark, DHBD-TMT can effectively adsorb uranium through the hydroxyl groups laced on the skeleton and reduce UVI to UIV in situ, leading to a higher adsorption capacity and selectivity of uranium. At the same time, the synergistic effect of the hydroquinone and triazine units in the extended π-conjugated skeleton significantly improve the photocatalytic activity of DHBD-TMT, and an additional UVI photocatalytic reduction mechanism can occur under visible light irradiation, allowing significantly higher the capacity and faster adsorption kinetics. [ABSTRACT FROM AUTHOR]

[Display omitted] • High selectivity imidazole was introduced as linkage in varying degree hydroxylation covalent organic polymers. • Benefiting from the introduction of hydroxyl groups, the uranium adsorption capacities were largely enhanced. • The TpDAB endowed prominent selectivity towards multiple metal ions including vanadium. • The hydroxyl groups significantly influenced the uranium coordination mechanism of imidazole functional group. Highly effective and reliable adsorbents for uranium extraction are vital significant for environmental protection and social development. Herein, inspired by the interaction between imidazole affinity ligand of histidine and uranium, a series of varying degree hydroxylation imidazole linked covalent organic polymers were developed for the first time via one step facile reaction without any post treatment between 2,4,6-triformylphloroglucinol (Tp), 2,4,6-triformylresorcinol (Bd), 2,4,6-triformylphenol (Hb) and 3,3′-diaminobenzidine (DAB), denoted as TpDAB, BdDAB, and HbDAB, respectively. Benefiting from the hierarchical structure of the covalent organic polymer and synergistic effects originating from hydroxyl groups and imidazole linkages, TpDAB, BdDAB, and HbDAB displayed as the promising adsorbents for uranium extraction with high extraction ability and fast capture kinetics. X-ray photoelectron spectroscopy results revealed that both nitrogen atoms in imidazole and oxygen atom in hydroxyl took part in uranium coordination. With the increasing of hydroxyl group amounts, TpDAB achieved highest extraction capacity of uranium. Furthermore, TpDAB with imidazole affinity group possessed eminent selectivity for uranium in the multiple metal ions solution, and especially overcome the unavoidable problem of vanadium interfering with amidoxime adsorption uranium. This work provided a promising uranium extraction strategy with high selectivity and easy preparation for environmental protection and human health. [ABSTRACT FROM AUTHOR]

We report the first example of vinylene-linked covalent organic framework (Tp-TMT) with enhanced uranium adsorption through combined selective ligand binding, chemical reduction and photocatalytic reduction. The dense hydroxyl functional groups on the Tp-TMT framework had good selectivity and excellent chemical reduction performance for U(VI). Meanwhile, the synergistic effect of hydroxyl groups and triazine unit significantly enhanced the photocatalytic reduction activity. Thus Tp-TMT exhibited incredible adsorption kinetics and capacity for uranium. [Display omitted] • COFs effectively capture uranium through three coordinated mechanisms. • Tp-TMT has excellent visible light conversion efficiency and low band gap. • Tp-TMT enhances uranium adsorption through selective ligand binding and reduction. • Tp-TMT exhibits incredible adsorption kinetics and capacity for uranium. So far, it remains a challenge to synthesize uranium adsorbents with robust stability, high adsorption capacity, excellent photocatalytic activity and easy regeneration. Herein, we report the first example of vinylene-linked covalent organic framework (Tp-TMT) with enhanced uranium adsorption through combined selective ligand binding, chemical reduction and photocatalytic reduction. The unique structure and excellent photocatalytic activity of Tp-TMT make it very suitable for photo-enhanced uranium adsorption through three synergistic mechanisms, thus exhibiting an outstanding uranium adsorption capacity (2362.4 mg g−1). In the dark, a large number of hydroxyl groups in the Tp-TMT framework serve as selective binding sites for uranium, and reduce part of U(VI) to U(IV), thereby greatly improving the adsorption capacity. Meanwhile, the synergistic effect of the triazine units and hydroxyl groups in the highly conjugated framework greatly decreases the optical band gap of Tp-TMT, and an additional U(VI) photocatalytic reduction process can occur under light irradiation, further increasing the adsorption kinetics and capacity. This work explored the structural and functional design of covalent organic frameworks for the adsorption and reduction of uranium in nuclear industry wastewater. [ABSTRACT FROM AUTHOR]

• Highly stable sp2 carbon-conjugated covalent organic framework (COF-PDAN-AO) was synthesized and characterization. • Acid and radiation resistant COF-PDAN-AO exhibits efficient adsorption of UO 2 2+ from radioactive wastewater. • COF-PDAN-AO possesses short adsorption equilibrium time and selectivity for uranium. • The emission of COF-PDAN-AO was selectively quenched upon adding UO 2 2+. Uranium is an important element in the nuclear industry while the discharge of radioactive wastewater can cause serious damages to the environment. In this work, an ultra-stable sp2 carbon-conjugated covalent organic framework (COF-PDAN-AO) is synthesized with amidoxime-substituted monomers for detection and efficient adsorption of uranium from radioactive wastewater. Abundant amidoxime groups laced on the open 1D channels of COF-PDAN-AO exhibit exceptional accessibility and the regular pores facilitate the mass transfer. Based on these features, COF-PDAN-AO achieves ultra-low detection limit of 6.5 nM, high uranium adsorption capacity (410 mg/g) and selective interaction with uranium. In addition, various spectroscopies verify COF-PDAN-AO possesses excellent radioresistance in acidic solution. Regeneration studies have shown that COF-PDAN-AO maintained good structural stability after seven cycles. These results indicate that our sp2 carbon conjugated COF can be potentially used for practical detection and adsorption of uranium from radioactive wastewater. This strategy can be extended to detection and extraction of other contaminants by designing the target ligand. [ABSTRACT FROM AUTHOR]