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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.

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.

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.

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.

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.

The effective removal of zwitterionic fluoroquinolone (FQ) antibiotics with high water solubility in wastewater is a key environmental challenge due to the inefficacy of conventional methods of wastewater treatment. In this work, zwitterionic covalent organic frameworks (Tp-MTABs) were synthesized through a solvothermal route using 5,5′,5″-methanetriyltris(2-aminobenzenesulfonic acid) (MTABs) as a zwitterionic linker and 1,3,5-triformylphloroglucinol (Tp) as neutral knots for efficient uptake of FQ antibiotics. Tp-MTABs compose of regular distributions of sulfonic acids and amines that produce zwitterionic binding sites, which produce complementary ion-pair interactions with zwitterionic FQ antibiotics. The charge on Tp-MTABs facilitates its initial self-exfoliation to few-layered ionic covalent organic nanosheets (iCONs) with controlled surface charge, which exposes more surface ionic sites and phenyl groups toward FQ antibiotics, improving ion-pair and π–π interactions between iCONs and FQ antibiotics. These iCONs with multiple active sites highly facilitated the process of antibiotics adsorption, boosting the adsorption kinetics and improving the selectivity towards FQ antibiotics. Tp-MTABs endows ultrafast adsorption rate (