2D covalent organic frameworks (2D COFs) have been recognized as a novel class of photoactive materials owing to their extended π‐electron conjugation and high chemical stabilities. Herein, a new ...covalent organic framework (Tph‐BDP) is facilely synthesized by using a porphyrin derivative and an organic dye BODIPY derivative (5,5‐difluoro‐2,8‐diformyl‐1,3,7,9‐tetramethyl‐10‐phenyl‐5H‐dipyrrolo1,2‐c:2′,1′‐f1,3,2diazabori‐nin‐4‐ium‐5‐uide) as monomers for the first time, and their unique photosensitive properties endow them excellent simulated oxidase activity under 635 nm laser irradiation that can catalyze the oxidation of 3,3′,5,5′‐tetramethylbenzidine (TMB). Further findings demonstrate that the presence of uranium (UO22+) can coordinate with imines of the oxidation products of TMB, thus modulating the charge transfer process of the colored products accompanied with intensive aggregation and remarkable color fading. This research provides a preparation strategy for COFs with excellent photocatalytic properties and nanozyme activity, and broadens the applications of the simple colorimetric methods for sensitive and selective radionuclide detection.
A new covalent organic framework is facilely synthesized and its unique photosensitive property endows excellent simulated oxidase activity that can catalyze the oxidation of 3,3′,5,5′‐tetramethylbenzidine (TMB). The presence of uranium can coordinate with imines of the oxidation products of TMB, thus modulating the charge transfer process of the colored products accompanied with intensive aggregation and remarkable color fading.
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.
Photoelectric and photocatalytic effects endow the covalent organic framework NDA‐TN‐AO with good anti‐biofouling activity. This occurs by generating biotoxic reactive oxygen species and promoting photoelectrons to reduce the adsorbed UVI to insoluble UIV, thereby improving the uranium adsorption capacity.
Electrochemiluminescence (ECL) plays a key role in analysis and sensing because of its high sensitivity and low background. Its wide applications are however limited by a lack of highly tunable ECL ...luminophores. Here we develop a scalable method to design ECL emitters of covalent organic frameworks (COFs) in aqueous medium by simultaneously restricting the donor and acceptor to the COFs' tight electron configurations and constructing high-speed charge transport networks through olefin linkages. This design allows efficient intramolecular charge transfer for strong ECL, and no exogenous poisonous co-reactants are needed. Olefin-linked donor-acceptor conjugated COFs, systematically synthesized by combining non-ECL active monomers with C
or C
symmetry, exhibit strong ECL signals, which can be boosted by increasing the chain length and conjugation of monomers. The present concept demonstrates that the highly efficient COF-based ECL luminophores can be precisely designed, providing a promising direction toward COF-based ECL phosphors.
The inherent features of covalent organic frameworks (COFs) make them highly attractive for uranium recovery applications. A key aspect yet to be explored is how to improve the selectivity and ...efficiency of COFs for recovering uranium from seawater. To achieve this goal, a series of robust and hydrophilic benzoxazole‐based COFs is developed (denoted as Tp‐DBD, Bd‐DBD, and Hb‐DBD) as efficient adsorbents for photo‐enhanced targeted uranium recovery. Benefiting from the hydroxyl groups and the formation of benzoxazole rings, the hydrophilic Tp‐DBD shows outstanding stability and chemical reduction properties. Meanwhile, the synergistic effect of the hydroxyl groups and the benzoxazole rings in the π‐conjugated frameworks significantly decrease the optical band gap, and improve the affinity and capacity to uranium recovery. In seawater, the adsorption capacity of uranium is 19.2× that of vanadium, a main interfering metal in uranium extraction.
Excellent photocatalytic activity, photothermal and photoelectric effects make Tp‐DBD produce biotoxic ROS, have good anti‐biofouling activity, and increase the adsorption rate and affinity of uranium binding sites, thereby improving the recovery capacity of uranium.
The type of reactions and the availability of monomers for the synthesis of sp
-c linked covalent organic frameworks (COFs) are considerably limited by the irreversibility of the C=C bond. Herein, ...inspired by the Claisen-Schmidt condensation reaction, two propenone-linked (C=C-C=O) COFs (named Py-DAB and PyN-DAB) are developed based on the base-catalyzed nucleophilic addition reaction of ketone-activated α-H with aromatic aldehydes. The introduction of propenone structure endows COFs with high crystallinity, excellent physicochemical stability, and intriguing optoelectronic properties. Benefitting from the rational design on the COFs skeleton, Py-DAB and PyN-DAB are applied to the extraction of radionuclide uranium. In particular, PyN-DAB shows excellent removal rates (>98%) in four uranium mine wastewater samples. We highlight that such a general strategy can provide a valuable avenue toward various functional porous crystalline materials.
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•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 AuCl4− in acidic system. The advantages of this feasible method facilitate effective gold recovery from low-cost electronic waste.
The high toxicity and mobility of hexavalent chromium (Cr(VI)) allow it to easily spread and bioaccumulate, and its detection is a major part of environmental protection. In this work, an innovative ...method is developed for preparation of cerium oxide nanorod-templated metal-organic frameworks (CeO
NRs-MOF). The in situ growth of MOF on the surface of CeO
nanorods (CeO
NRs) enhances its oxidase-like activity. In the presence of a trace amount of Cr(VI), CeO
NRs-MOF can significantly accelerate the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB) due to Cr(VI)-boosted oxidation, resulting in a blue colored oxidation product. It can detect Cr(VI) over a range of 0.03-5 μM with high selectivity. Moreover, this method can be applied to the detection of Cr(VI) in different water environment samples with satisfactory recoveries, demonstrating the potential application of CeO
NRs-MOF for the direct monitoring of Cr(VI) in environmental water systems. Thus, this work provides a facile host-templated MOF preparation method, which could possibly be extended to other fields.
Due to the low efficiency of traditional sewage treatment methods, the effective removal of zwitterionic fluoroquinolone (FQs) antibiotics is of vital significant for environment protection. In this ...work, a SO3H-anchored covalent organic framework (TpPa-SO3H) was deliberately designed by linking phenolic trialdehyde with triamine through Schiff reaction, then low-content Tb3+ ions were loaded onto covalent organic framework according to wet-chemistry immersion dispersion method which benefitting for efficient FQs antibiotics uptaking. Tb@TpPa-SO3H functionalized with regularly distributed sulfonic acid groups and terbium ions which could provide difunctional binding sites. Tb3+ sites could capture carboxylic acid group of FQs molecules according to the complexes coordination effect and sulfonic acid sites play a significant role in the adsorption of FQs molecules through electrostatic interaction with amine group. Tb@TpPa-SO3H with dual complementary function sites exhibited ultra-fast adsorption kinetics (< 2 min, average over 99% removing rate) and high adsorption capacities of 989, 956, and 998 mg g−1 for Norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), respectively. Furthermore, Tb@TpPa-SO3H showed excellent selectivity for the adsorption of FQs in tanglesome system. This work not only explored synergistic adsorption in ion-functionalized 2D covalent organic framework with dual binding sites, but also delineated a promising strategy for the elimination of organic pollutants in environmental remediation.
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•A difunctional Covalent Organic Framework Hybrid Material was prepared for efficient uptake of fluoroquinolone antibiotics.•Difunctional Tb@TpPa-SO3H exhibits outstanding adsorption capacity and short adsorption equilibrium time for FQs.•Tb@TpPa-SO3H shows excellent selectivity for the adsorption of FQs in tanglesome systems.•Plausible FQs adsorbed mechanisms were coordination with metal and electrostatic interaction.
Heavy metal ion pollution has threatened environmental and human safety. Therefore, there is a remarkable demand to detect heavy metal ions in a fast, sensitive, and selective way. Although ...conventional sensors have been designed and widely applied in heavy metal ion determination, they present many limitations and challenges. Graphene-based nanotechnology overcomes these challenges and endows the sensing platform a better performance. In this overview, studies concerning graphene-based optical nanosensors for heavy metal ion detection have been summarized, paying special attention to sensors based on graphene, graphene oxide, and graphene quantum dots. In addition, the prospects and developing trends of nanosensors for heavy metal ion analysis are also proposed.
•Graphene-based hybridized nanocomposites for metal ion optical detection were reviewed.•Graphene or GO as fluorescence probes for heavy metal ion detection was summarized.•Graphene or GO as the fluorescence quencher for heavy metal ion analysis was described.•Applications of GQD and CD probes in heavy metal ion sensing were discussed.
Nanomaterials with enzyme mimetic activity have attracted extensive attention, especially in the regulation of their catalytic activities by biomolecules or other polymers. Here, a covalent organic ...framework (Tph‐BT COF) with excellent photocatalytic activity is constructed by Schiff base reaction, and its mimetic oxidase activity and peroxidase activity is inversely regulated via single‐stranded DNA (ssDNA). Under light‐emitting diode (LED) light irradiation, Tph‐BT exhibited outstanding oxidase activity, which efficiently catalyzed oxidation of 3,3′,5,5′‐tetramethylbenzidine (TMB) to produce blue oxTMB, and ssDNA, especially those with poly‐thymidine (T) sequences, can significantly inhibit its oxidase activity. On the contrary, Tph‐BT showed weak peroxidase activity, and the presence of ssDNA, particularly poly‐cytosine (C) sequences, can remarkably enhance the peroxidase activity. The influence of base type, base length, and other factors on the activities of two enzymes is also studied, and the results reveal that the adsorption of ssDNA on the surface of Tph‐BT prevented intersystem crossing (ISC) and energy transfer processes to reduce 1O2 generation, while the electrostatic interaction between ssDNA and TMB enhanced Tph‐BT's affinity for TMB to facilitate the electron transfer from TMB to •OH. This study investigates multitype mimetic enzyme activities of nonmetallic D‐A conjugated COFs and demonstrates their feasibility of regulation by ssDNA.
A D‐A covalent organic framework (Tph‐BT) with unique mimetic oxidase and peroxidase activities has been synthesized. The outstanding oxidase activity of Tph‐BT can be significantly inhibited by the adsorption of single‐stranded DNA (ssDNA), while the weak peroxidase activity of Tph‐BT can be remarkably enhanced upon the addition of ssDNA.
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