Search

[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]

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]

[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 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]