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Covalent organic frameworks (COFs) have been proposed for electrochemical energy storage, although the poor conductivity resulted from covalent bonds limits their practical performance. Here, we propose to introduce noncovalent bonds in COFs through a molecular insertion strategy for improving the conductivity of the COFs as supercapacitor. The synthesized COFs (MI−COFs) establish equilibriums between covalent bonds and noncovalent bonds, which construct a continuous charge transfer channel to enhance the conductivity. The rapid charge transfer rate enables the COFs to activate the redox sites, bringing about excellent electrochemical energy storage behavior. The results show that the MI−COFs exhibit much better performance in specific capacitance and capacity retention rate than those of most COFs‐based supercapacitors. Moreover, through simply altering inserted guests, the mode and strength of noncovalent bond can be adjusted to obtain different energy storage characteristics. The introduction of noncovalent bonds is an effective and flexible way to enhance and regulate the properties of COFs, providing a valuable direction for the development of novel COFs‐based energy storage materials. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) have been proposed for electrochemical energy storage, although the poor conductivity resulted from covalent bonds limits their practical performance. Here, we propose to introduce noncovalent bonds in COFs through a molecular insertion strategy for improving the conductivity of the COFs as supercapacitor. The synthesized COFs (MI−COFs) establish equilibriums between covalent bonds and noncovalent bonds, which construct a continuous charge transfer channel to enhance the conductivity. The rapid charge transfer rate enables the COFs to activate the redox sites, bringing about excellent electrochemical energy storage behavior. The results show that the MI−COFs exhibit much better performance in specific capacitance and capacity retention rate than those of most COFs‐based supercapacitors. Moreover, through simply altering inserted guests, the mode and strength of noncovalent bond can be adjusted to obtain different energy storage characteristics. The introduction of noncovalent bonds is an effective and flexible way to enhance and regulate the properties of COFs, providing a valuable direction for the development of novel COFs‐based energy storage materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • Cu-based metal covalent organic framework (Cu-TMT) was prepared for the extraction of uranium. • Cu-TMT has unsaturated Cu centers that serve as chemical reduction sites. • Cu-TMT has excellent visible light conversion efficiency and low band gap. • Cu-TMT reduced uranium by chemical reduction and photocatalytic reduction reached 1438.8 mg g−1. The reduction of hexavalent uranium to tetravalent uranium is an effective strategy for controlling uranium contamination in wastewater. Herein, a C C bonded metal-covalent organic framework (Cu-TMT) was synthesized via the Aldol condensation reaction by using the metal cluster Cu 3 (PyCA) 3 and 2,4,6-trimethyl-1,3,5-triazine (TMT) for the chemical and photocatalytic synergistic reduction of uranium. In the Cu-TMT, the low-valent Cu in the metal clusters provides the framework with numerous distributed redox sites being capable of chemically reducing UVI. Meanwhile, the encapsulating Cu clusters in long-range ordered frameworks can provide fast transport channels for intramolecular charge transfer and effectively inhibit electron/hole complexation, making Cu-TMT suitable for photocatalytic reduction of uranium. The chemical reduction of uranium by Cu-TMT was verified under light-avoidance conditions, reaching 659.5 mg g−1. After exposure of Cu-TMT to light, the amount of reduced uranium further increases to 1438.8 mg g−1 with 98.1 % removal rate of actual uranium containing wastewater. This study not only expands the range of applications of variable valence metal covalent organic frameworks, but also provides unique insights into the effective combination of chemical and photocatalytic reduction strategies for removing UVI in a single material. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phosphate functionalized COF/rGO was synthesized using post-synthetic modification. • Tb-BD-P/rGO exhibited excellent physicochemical stability and rapid uranyl mass transfer ability. • TB-BD-P/rGO enabled photoelectrothermal synergistic photocatalytic reduction of uranium. • Tb-BD-P/rGO performed excellent removal rates (>95 %) in actual strong acid nuclear wastewater. Photocatalytic reduction is becoming an effective method to remove UVI from uranium mine wastewater. Herein, 1,3,5-benzotrialdehyde (Tb) and 4,4′-diaminobiphenyl (BD) used as monomers of covalent organic framework (COF) are in situ growth on graphene oxide (GO) surfaces to obtain Tb-BD/rGO. Then, Tb-BD/rGO is converted into Tb-BD-P/rGO by asymmetric hydrogen phosphorylation, which is served as a new material for photocatalytic reduction of uranium via photoelectrothermal synergy. Benefiting from the transformation of dynamic imine bonds into irreversible carbon–nitrogen single bonds, Tb-BD-P/rGO expresses remarkable chemical and thermal stability. The introduction of phosphate groups improve the electronegativity and hydrophilicity of Tb-BD-P/rGO, which contribute to rapid transportation of uranium. In addition, the introduction of rGO achieves excellent photothermal conversion, accelerating the adsorption kinetics of uranium. Meanwhile, the π-π interaction between Tb-BD-P and rGO promotes inter-interfacial electron transfer and reduces the complexation of electron-hole pairs during the photocatalytic process, further improving photocatalytic performance. Therefore, Tb-BD-P/rGO demonstrates exceptional removal uranium rates (>95 %) in uranium mine wastewater by synergistically photoelectrothermal integration, offering a pathway for developing multifunctional and integrated photocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ti-MOF@DATp was developed by using Ti-MOF as core and in-situ growing DATp shells on its surface. • A Z-Scheme heterojunction was created through covalent bonds between Ti-MOF and DATp. • The Ti-MOF@DATp enables tetracycline passing through the DATp shell while selectively capturing U(VI). • Ti-MOF serves as the site for photooxidation tetracycline, while DATp serves as the site for photoreduction U(VI). Uranium and antibiotics coexisting in natural water bodies pose a significant threat to the environment and human health. Herein, Ti-MOF@DATp was developed by using a metal–organic framework (Ti-MOF) as the core and in-situ growing covalent organic framework (DATp) shells on its surface for simultaneous photocatalytic reduction U(VI) and oxidation tetracycline. The staggered energy levels between Ti-MOF and DATp create a Z-Scheme heterojunction through covalent bonds between them, promoting the charge and holes transfer with enhancing the photocatalytic performance. The Ti-MOF@DATp enables tetracycline passing through the DATp shell while selectively capturing U(VI), then Ti-MOF functions as the site for photooxidation tetracycline, while DATp serves as the site for photoreduction U(VI). The oxidation and reduction of sites can be effectively separated, improving the utilization efficiency of photogenerated electrons and holes. Hence, Ti-MOF@DATp can effectively accomplish the simultaneous photocatalytic removal of 96% U(VI) and 90% tetracycline of their mixture. In comparison to the removal efficiency of 89% for U(VI) and 77% for tetracycline when removal alone, a notable enhancement in performance is observed. Particularly, the removal rate constant of the U(VI) and tetracycline mixture is 55 times higher than that of U(VI) alone and 4 times higher than that of tetracycline alone. Therefore, bifunctional photocatalysts offer an effective approach to tackling complex environmental challenges. [ABSTRACT FROM AUTHOR]

The radioactive ion U(VI) and organophosphorus pollutants in sewage do great harm to the ecological environment and human health. Bifunctional photocatalyst MOF525@BDMTp was prepared by in-situ covalent bridging method, and U(VI) and chlorpyrifos (CP) were removed by one-to-two strategy. MOF525@BDMTp had high carrier migration performance and conformed to the type-II heterojunction. Under light conditions, electrons were transferred from MOF525 to BDMTp due to the action of the built-in electric field, increasing the electron density of BDMTp and thus activating the U(VI) binding sites. BDMTp interacted with S and N atoms in CP to promote its hydrolysis and oxidation by h+ and ·O 2 -. Thus, MOF525@BDMTp guaranteed the simultaneous reduction of U(VI) on BDMTp and the oxidation of CP on MOF525. Therefore, designing functional integrated composites is an effective means to improve the photocatalytic performance of composite materials in complex environments. [Display omitted] • MOF525@BDMTp was prepared by in-situ covalent bond bridging method. • MOF525@BDMTp can adsorb both U (VI) and chlorpyrifos. • Type-II heterojunction in MOF525@BDMTp improved electron-hole separation. • The presence of U(VI) and CP improved the removal performance of each other. [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]

The decline of fossil fuels is fostering research on carbon–neutral fuels such as nuclear energy, yet uranium supply is limited by actual techniques of uranium extraction from seawater. In particular, biofouling by marine bacteria and adsorbent instability are major drawbacks. Here we synthesized a novel amidoxime-functionalized antibacterial covalent organic framework that displays high stability and inhibits more than 90% the growth of marine bacteria, thus resulting in an enhanced uranium recovery capacity of 6.64 mg/g. Meanwhile, due to its exceptional fluorescence properties, the adsorbent can also be applied to highly sensitive on-site and real-time monitoring of UO22+. [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 covalent organic framework (DANT-BTT) with a D-A structure was synthesized based on naphthalimide. • DANT-BTT exhibits excellent chemical stability and photocatalytic properties. • Protonated DANT-BTT with superior photocatalytic capability and higher selectivity for uranium. • DANT-BTT has excellent removal efficiency for uranium at pH 1. Efficient removal of UO 2 2+ from radioactive wastewater under strong acid conditions remains a significant challenge due to the competition of excess H+ for adsorption and reduction sites. Here, covalent organic framework with complete charge separation and protonation properties (DANT-BTT) was synthesized for efficient removal of UO 2 2+ under strong acids. The DANT-BTT with strong electron-deficient naphthalimide significantly extended light absorption and enhanced intramolecular charge transfer, which significantly improve the separation efficiency of electrons and holes. Additionally, the auxiliary coordination of hydroxyl groups after protonation provides unparalleled selectivity for UO 2 2+ in strong acids, effectively preventing the competition of H+ for adsorption sites. Protonation of nitrogen atoms and ketones also extends light absorption and store electrons, further enhancing the photocatalytic performance of DANT-BTT. Consequently, DANT-BTT can achieve 71 % photoreduction UO 2 2+ efficiency (pH 1) after 60 min irradiation, where dark adsorption accounts for 43 %. This work provides a strategy for the efficient reduction of U(VI) under strong acids. [ABSTRACT FROM AUTHOR]

Uranium is a key resource for the development of the nuclear industry, and extracting uranium from the natural seawater is one of the most promising ways to address the shortage of uranium resources. Herein, a semiconducting covalent organic framework (named NDA‐TN‐AO) with excellent photocatalytic and photoelectric activities was synthesized. The excellent photocatalytic effect endowed NDA‐TN‐AO with a high anti‐biofouling activity by generating biotoxic reactive oxygen species and promoting photoelectrons to reduce the adsorbed UVI to insoluble UIV, thereby increasing the uranium extraction capacity. Owing to the photoinduced effect, the adsorption capacity of NDA‐TN‐AO to uranium in seawater reaches 6.07 mg g−1, which is 1.33 times of that in dark. The NDA‐TN‐AO with enhanced adsorption capacity is a promising material for extracting uranium from the natural seawater. [ABSTRACT FROM AUTHOR]

Uranium is a key resource for the development of the nuclear industry, and extracting uranium from the natural seawater is one of the most promising ways to address the shortage of uranium resources. Herein, a semiconducting covalent organic framework (named NDA‐TN‐AO) with excellent photocatalytic and photoelectric activities was synthesized. The excellent photocatalytic effect endowed NDA‐TN‐AO with a high anti‐biofouling activity by generating biotoxic reactive oxygen species and promoting photoelectrons to reduce the adsorbed UVI to insoluble UIV, thereby increasing the uranium extraction capacity. Owing to the photoinduced effect, the adsorption capacity of NDA‐TN‐AO to uranium in seawater reaches 6.07 mg g−1, which is 1.33 times of that in dark. The NDA‐TN‐AO with enhanced adsorption capacity is a promising material for extracting uranium from the natural seawater. [ABSTRACT FROM AUTHOR]

Construction of covalent organic frameworks (COFs)-based nanozymes is of great importance for the extensive applications in catalysis and sensing fields. In this work, a two-dimensional COF (DAFB-DCTP COF) was fabricated via Knoevenagel condensation reaction. The integration of catalytically active sites of pyridine groups into the donor-acceptor (D-A) conjugated skeleton endows DAFB-DCTP COF with both hydrolytic and photosensitive properties. The DAFB-DCTP COF can be utilized as an artificial enzyme with selective and photo-enhanced catalytic efficiency, facilitating its application in photocatalytic degradation of hydrolase substrates (p- nitrophenyl acetate, p NPA) by nucleophilic reaction and further realizing colorimetric detection of the nanozyme inhibitor of organophosphorus nerve agent (diethyl cyanophosphonate, DCNP). The distinct color changes could be distinguished by naked eyes even at a low DCNP concentration, and the versatile smartphone analysis featured with reliability and simplicity. For the first time, the COFs' intrinsic hydrolase activity depending on their structural characteristics was investigated in synergy with the photosensitive performance originating from their photoelectric features. The present contribution provides a promising direction towards construction of colorimetric sensing platform based on the regulation of COFs' non-oxidoreductase activity under visible light irradiation. A novel photosensitive and hydrolytically active covalent organic framework (DAFB-DCTP COF) is constructed, which can be utilized as an artificial enzyme for photocatalytic degradation of ester substrates via nucleophilic reaction, and thus colorimetric detection of the organophosphorus nerve agent can be realized due to its inhibition effect on the mimic hydrolase activity and the photosensitive property of DAFB-DCTP COF. [Display omitted] • A D-A conjugated COF with pyridine groups is successfully constructed. • The COF nanozyme involves selective and photo-enhanced hydrolase activities. • Organophosphorus nerve agents can inhibit the nanoenzymatic activity of the COF. • Nerve agents can be colorimetrically detected by naked eyes or versatile smartphones. [ABSTRACT FROM AUTHOR]

Plasmonic photocatalysis is an effective strategy to solve radioactive uranium hazards in wastewater. A plasmonic photocatalyst Bi/Bi 2 O 3−x @COFs was synthesized by in-situ growth of covalent organic frameworks (COFs) on Bi/Bi 2 O 3−x surface for the U(VI) adsorption and plasmonic photoreduction in rare earth tailings wastewater. The presence of oxygen vacancy in Bi/Bi 2 O 3−x and Schottky potential well formed by Bi and Bi 2 O 3−x interface increased the number of free electrons, which induced localized surface plasmon resonance (LSPR) and enhanced the light absorption performance of composites. In addition, oxygen vacancy improved the Fermi level of Bi/Bi 2 O 3−x , leading to another potential well between Bi 2 O 3−x and COFs interface. The electron transport direction was reversed, thus increasing the electron density of COFs layer. COFs was an N-type semiconductor with specific binding U(VI) groups and suitable band structure, which could be used as an active reaction site. Bi/Bi 2 O 3−x @COFs had 1411.5 mg g−1 removal capacity and high separation coefficient for U(VI) due to the synergistic action of photogenerated electrons and hot electrons. Moreover, the removal rate of uranium from rare earth tailings wastewater by regenerated Bi/Bi 2 O 3−x @COFs was over 93.9%. The scheme of introducing LSPR and Schottky potential well provides another way to improve the photocatalytic effect. [Display omitted] • Bi/Bi 2 O 3−x @COFs with core-shell structure was synthesized in-situ. • Oxygen vacancies in Bi 2 O 3−x induced LSPR and increased light absorption. • The double Schottky potential well increased the electron density of COFs. • U(VI) was reduced by the synergistic action of photogenerated and hot electrons. • Regenerated Bi/Bi 2 O 3−x @COFs had high cyclic stability. [ABSTRACT FROM AUTHOR]

Previous researches of covalent organic frameworks (COFs) have shown their potential as fluorescent probes, but the regulation of their optical properties and recognition characteristics still remains a challenge, and most of reports required complicated post-decoration to improve the sensing performance. In this context, we propose a novel in-situ strategy to construct uracil-conjugated COFs and modulate their fluorescence properties for sensitive and selective mercury(II) detection. By using 1,3,6,8-tetrakis(4-formylphenyl)pyrene (TFPPy) and 1,3,6,8-tetrakis(4-aminophenyl)pyrene (TAPPy) as fundamental blocks and 5-aminouraci (5-AU) as the functional monomer, a series of COFs (Py-COFs and Py-U-COFs-1 to Py-U-COFs-5) with tunable fluorescence were solvothermally synthesized through an in-situ Schiff base reaction. The π-conjugated framework serves as a signal reporter, the evenly and densely distributed uracil acts as a mercury(II) receptor, and the regular pores (channels) make the rapid and sensitive detection of the mercury(II) possible. In this research, we manage to regulate the crystalline structure, the fluorescence properties, and the sensing performance of COFs by simply changing the molar ratio of precursors. We expect this research to open up a new strategy for effective and controllable construction of functionalized COFs for environmental analysis. An in-situ strategy is proposed to construct uracil-conjugated COFs and modulate their fluorescence properties for sensitive and selective mercury(II) detection. The π-conjugated framework serves as a signal reporter, the evenly and densely distributed uracil acts as a mercury(II) receptor, and the regular pores (channels) make the rapid and sensitive detection of the mercury(II) possible. [Display omitted] • A novel in-situ strategy was proposed to construct uracil-conjugated COFs. • The crystalline structure and the fluorescence property of COFs can be facilely modulated. • The functionalized COFs demonstrate tunable recognition characteristics toward mercury(II). • Mercury(II) can be sensitively and selectively detected based on the fluorescence quenching. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SnS 2 -covalent organic framework van der Waals heterojunction (SnS 2 COF) was constructed. • With good photoelectric properties, SnS 2 COF can realize separation and transfer of electron-hole. • The electron flow path of heterojunction conforms to Z-scheme by experimental study and theoretical calculation. • SnS 2 COF can effectively reduce and remove U (VI) from rare earth tailings wastewater under UV/Vis light. Uranium removal by photocatalytic reduction is one of the most promising methods to reduce radioactive contamination in wastewater. Herein, a Z-scheme van der Waals heterojunction photocatalyst (SnS 2 COF) was synthesized in situ by combining covalent organic frameworks (COF) with semiconductor (SnS 2) for U (VI) reduction in rare earth tailings wastewater. The synthesis method of van der Waals heterojunction is simple and solves the problem of no hanging bond in composite components. In this heterojunction, large areas of van der Waals interaction form high-speed electron transport channels. In addition, it is deduced that SnS 2 COF fits the Z-scheme heterojunction electron transport mode through the theoretical calculation of the ground state and excited state electron density difference and the related band structure. Under the photoexcitation, the direction of electron flow is reversed, which further promotes the separation of the photogenerated electron (e−)-hole (h+) under the action of the built-in electric field, maintains the high reducibility of the conduction band, and avoids the photocorrosion of SnS 2. Compared with inorganic-inorganic heterojunction, SnS 2 COF has a wider light absorption range, more active sites, and higher e−-h+ separation and transfer efficiency. Therefore, it had a higher U (VI) reduction removal capacity, up to 1123.3 mg g−1, far surpassing the SnS 2 and COF counterparts under ultraviolet/visible light. And the U (VI) removal rate reached 98.5 % in rare earth tailings wastewater. The design concept of organic–inorganic heterojunction materials provides an alternative strategy for improving the photocatalytic performance. [ABSTRACT FROM AUTHOR]

Efficient extraction of radioactive 99TcO 4 - from strong acid/base solutions by porous adsorbents is extremely desirable but remains a great challenge. To overcome the challenge, here we report the first example of an olefin-linked cationic covalent organic framework (COF) named BDBI-TMT with excellent acid, base and radiation stability is synthesized by integrating robust imidazolium salt-based linkers with triazine building blocks. BDBI-TMT shows an ultra-fast adsorption kinetics (equilibrium is reached within 1 min) and an excellent ReO 4 - (a non-radioactive surrogate of 99TcO 4 -) capture capacity of 726 mg g−1, which can be attributed to the abundance of precisely tailored imidazolium salt-based units on the highly accessible pore walls of the ordered pore channels. Furthermore, the formation of the highly conjugated bulky alkyl skeleton enhances the hydrophobicity of BDBI-TMT, which significantly improves not only the affinity toward ReO 4 -/99TcO 4 - but also the chemical stability, allowing selective and reversible extraction of ReO 4 -/99TcO 4 - even under extreme conditions. This work demonstrates the great potential of olefin-linked cationic COFs for ReO 4 -/99TcO 4 - extraction, providing a new avenue to construct high-performance porous adsorbents for radionuclide remediation. [Display omitted] • Explore robust olefin-linked cationic covalent organic framework (COF) for efficient extraction of ReO 4 −/99TcO 4 −. • This is the first example of olefin-linked cationic COF (BDBI-TMT) for high-performance ReO 4 −/99TcO 4 − removal. • This work provides a new avenue for constructing high-performance porous adsorbents for ReO 4 −/99TcO 4 − remediation. [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]

• Three-dimensional luminescent covalent organic framework (TAPM-DHBD) for reversible uranium detection and extraction. • This is the first example of three-dimensional fluorescent covalent organic framework for simultaneous uranium detection and extraction. • TAPM-DHBD is suitable for sensitive and on-site monitoring the radioactive uranium contamination of the extracted water. • TAPM-DHBD exhibits an exceptional uranium extraction capacity as well as fast kinetics. Uranium is a key fuel for nuclear reactions, but it also causes serious public health concerns to human beings when leaked into the environment. Exploring new strategies for simultaneous uranium detection and extraction is highly desirable for public health and environmental protection. Herein, a hydroxyl-functionalized 3D covalent organic framework (termed TAPM-DHBD) with strong fluorescence and 3D interconnected pore channels is synthesized and evaluated for uranium detection and extraction. TAPM-DHBD exhibits an exceptional uranium extraction capacity of 955.3 mg g−1 as well as fast kinetics due to the plentiful selective binding sites on the extremely accessible pore channels of 3D interconnected micropore skeleton. Interestingly, due to the signal amplification of the 3D conjugated skeleton, it has a rapid-response time of 2 s and an ultra-low detection limit of 4.08 nM UO 2 2+ suitable for sensitive and on-site monitoring the radioactive uranium contamination of the extracted water. Furthermore, TAPM-DHBD exhibits excellent regenerable performance at least six cycles. This study provides a new strategy for constructing high-performance 3D COFs for radioactive contamination monitoring and strategic nuclides extraction. [ABSTRACT FROM AUTHOR]

[Display omitted] • COFs and CNTs composites were synthesized by in-situ synthesis. • The synergistic effect improved the adsorption capacity and selectivity. • The removal mechanism of samples was clarified through various characteristic modes. • The problem of U (VI) removal from the rare earth tailings wastewater had been solved. The wastewater containing uranium produced in the mining process is harmful to the environment and life safety due to the inherent biotoxicity and radioactivity of uranium. In this paper, 4,4′-diamino-[1,1′-biphenyl]-3,3′-diol and 2,4,6-triformylphloroglucinol were in situ synthesized β -ketoenamine covalent organic frameworks (COFs) on the surface of carbon nanotubes (CNTs) to obtain a composite of CNT/COF-OH for removal uranium in the rare earth tailings wastewater. Grafting COFs with a large number of specific uranium-binding groups and redox-active sites on the surface of CNTs, CNT/COF-OH can effectively enhance the uranium ion selectivity and adsorption capacity. Furthermore, CNTs have good electron transport capacity and π-conjugation properties, electrons can be effectively transferred from CNTs to COFs, which increases the electron density of the adsorption functional groups, resulting in an increase of the adsorption energy and reductive activity for U (VI), thus improving the removal efficiency. In addition, the skeleton of COFs can be supported by CNTs, thus reducing collapse. Through the synergistic effect of composite, CNT/COF-OH had a good uranium adsorption capacity of 518.2 mg g−1. The adsorption capacity of CNT/COF-OH was increased by 390.7 %, 54.6 %, and 84.5 % compared with those of single CNTs, COF-OH, and mixed CNT + COF-OH, respectively. The selective separation coefficient of CNT/COF-OH was 1.6 times higher than that of COF-OH. The experiment of uranium removal was carried out in the rare earth tailings wastewater using CNT/COF-OH, the removal rate reached 96.7 %. The COFs modified CNTs with synergistic effect have important theoretical and practical significance for the safety problems caused by harmful ions in wastewater. [ABSTRACT FROM AUTHOR]

Mechanism diagram. Through the structural design at the molecular level, the ECL-COF with electrocatalytic performance and excellent electronic structure was obtained, which display an adjustable easily potential ECL platform. Meanwhile, the advanced COF'ECL platform was developed for accurate monitoring of Lu3+, indicating the inestimable application potential of COFs in environment field. [Display omitted] • The azine-linked COFs are prepared for precise ECL performance regulation. • COFs display decrease of reduction potential and increase of intensity in ECL. • Introducing nitrogen into COFs bring electrocatalysis for ECL enhancement. • COFs show efficiently carrier transport for improving ECL. • A novel COF-ECL platform is structured for Lu3+ detection. Covalent organic frameworks (COFs) have emerged as a novel class of electrochemiluminescence (ECL) materials on account of its highly tunable structure and versatile properties. However, decoding the ECL property and its luminophor structure to improve the luminous performance remains challenging, which hinders its deeper development and wider application. Herein, by condensing triphenylarene aldehydes with varying number of nitrogen atoms with 2,4,6-trimethylbenzene-1,3,5-tricarbonitrile, a series of COFs were prepared to regulate the ECL potential, opening up a new way to precisely improve ECL performance. The electron and spatial changes in the precursor are transferred to the generated COFs skeleton, resulting in a progressively decrease in the reduction potential and a gradual increase intensity in ECL with the precise increase of nitrogen content in the skeleton. Introduction of nitrogen into COFs brings electrocatalysis and planarization of the framework for more efficiently carrier transport. The conclusion is confirmed by optical, electrical tests, as well as density functional theory calculations. As a proof-of-methodology, an ECL method was developed for the selective determination of lutetium ion with a detection limit as low as 1.6 nM (S/N = 3). This work exhibits that the advanced potential-tunable ECL-COFs can be obtained accurately and easily through design structure at the molecular level, which is expected to promote the exploration of the relationship between ECL potential and framework structure, and further apply to environment-related sensing analysis. [ABSTRACT FROM AUTHOR]

We proposed a strategy to synergistically enhance uranium capture capacity through photothermal desalination, and prepared a COF hydrogel (KTG) through a simple process for the first time. KTG with ideal broadband light absorption capacity could be used as an outstanding photothermal conversion material. Meanwhile, the built-in elastic honeycomb structure endowed the KTG with good mechanical properties and adequate water transport performance that accelerated the diffusion and mass transfer ability of uranyl. Under a simulated sunlight, the adsorption capacity, selectivity, adsorption rate and cycle capacity of uranium could be significantly improved. Moreover, benefiting from the outstanding photocatalytic performance, KTG exhibited a high anti-fouling activity against marine biological entities, thereby achieving long-term efficient uranium adsorption and solar desalination. [Display omitted] • The first example of COF hydrogel for solar desalination and uranium recovery. • COF hydrogel for synergistically enhance uranium capture through photothermal desalination. • COF hydrogel shows a high evaporation rate and exceptional uranium recovery capacity. • COF hydrogel has high anti-biofouling activity and good reusability. Capturing of uranium from the natural seawater is considered to be one of the most promising methods to meet the current demand for nuclear energy. Herein, we prepared a reduced graphene oxide-based (rGO-based) covalent organic framework hydrogel (KTG) with three-dimensional porous structure as a platform for enhancing uranium capture capacity through photothermal desalination. Under light irradiation, the KTG produces a local heat that can be used to generate steam while promoting the rapid diffusion of uranium inside the hydrogel 3D network, thereby increasing the adsorption efficiency and capacity of uranium. KTG can achieve exceptional uranium capture capacity (521.6 mg g−1) under one sun irradiation, which is 42.4% higher than that under dark conditions. In addition, excellent photocatalytic activity and mechanical properties make KTG possess high anti-biofouling activity, good reusability, and achieving continuous uranium capture and solar distillation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Triformylphloroglucinol and thiosemicarbazide as precursors for synthesizing TpTsc. • TpTsc with excellent adsorption capacity of gold shows higher than most adsorbents. • Dual functions of adsorption and reduction enhance gold adsorption capacity of TpTsc. • TpTsc can selectively extract gold from real electronic waste liquids. Recovering precious metals from electronic equipment waste involves significant environmental and economic benefits. In this paper, a covalent organic framework, named as TpTsc COF, was synthesized by using flexible alkyl amine thiosemicarbazide (Tsc) and 1,3,5-triformylphloroglucinol (Tp) as precursors for extracting gold from actual electronic waste. The results show that it has favorable selectivity, high recycling and groundbreaking adsorption capacity (4400.23 mg g−1). Such excellent adsorption capacity can be attributed to the improved crystallinity by irreversible enol-to-tautomerism of Tp, the abundant functional group sites in Tsc, and the efficient reduction of gold by thiourea. The adsorption process can be well fitted with the pseudo-second-order kinetic model and Langmuir mode, which is characterized by the coordination between Au (III) and S, N, O atoms in COF, as well as the electrostatic interaction between protonated amino groups and AuCl 4 − in acidic system. The advantages of this feasible method facilitate effective gold recovery from low-cost electronic waste. [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]

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]