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The development of adsorbents for efficient and highly selective seawater extraction of uranium was instrumental in fostering sustainable progress in energy and addressing the prevailing energy crisis. However, the complex background composition of the marine environment, including radionuclides, organic pollutants, and a large number of co-existing heavy metal ions, were non-negligible obstacles to the extraction of uranium from seawater. The present investigation successfully employed a self-templated approach to synthesize porous nitrogen-doped carbon (PNC) derived from COF, which exhibited tremendous potential as an adsorbent for pollutant removal in environmental treatment. LZU1@PNC not only retained the structural features of the original COF-LZU1, but also overcame the acid-base instability problem commonly found in COFs. Subsequently, the removal process of two typical water pollutants on the material was investigated using 2,4-DCP and [UO2(CO3)3]4-. The results demonstrated that LZU1@PNC exhibited superior removal performance for the target pollutants compared to COF-LZU1, owing to its larger specific surface area and abundant defect structure. After six desorption-regeneration cycles, LZU1@PNC still maintained a high removal rate of the target contaminants, demonstrating the stability of this material and its excellent recyclability. In addition, based on various characterization techniques, the removal mechanism of 2,4-DCP was presumed to be mainly electrostatic attraction, hydrogen bonding, and π-π stacking interactions. Conversely, the elimination process of [UO2(CO3)3]4- predominantly relied on surface complexation phenomena. The present investigation provided new perspectives and stimulated a broader study of other COF-derived carbon materials and their modifications as adsorbents for uranium extraction from seawater and other applications.

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Rapid, on-site measurement of ppm-level humidity in real time remains a challenge. In this work, we fabricated a few micrometer thick, ß-ketoenamine-linked covalent organic framework (COF) membrane via interfacially confined condensation of 1,3,5-tris-(4-aminophenyl)triazine (TTA) with 1,3,5-tri-formylphloroglucinol (TP). Based on the super-sensitive and reversible response of the COF membrane to water vapor, we developed a high-performance film-based fluorescence humidity sensor, depicting unprecedented detection limit of 0.005 ppm, fast response/recovery (2.2 s/2.0 s), and a detection range from 0.005 to 100 ppm. Remarkably, more than 7,000-time continuous tests showed no observable change in the performance of the sensor. The applicability of the sensor was verified by on-site and real-time monitoring of humidity in a glovebox. The superior performance of the sensor was ascribed to the highly porous structure and unique affinity of the COF membrane to water molecules as they enable fast mass transfer and efficient utilization of the water binding sites. Moreover, based on the remarkable moisture driven deformation of the COF membrane and its composition with the known polyimide films, some conceptual actuators were created. This study brings new ideas to the design of ultra-sensitive film-based fluorescent sensors (FFSs) and high-performance actuators.

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Recently, the misuse of organic arsenic feed additives, such as roxarsone (ROX), has increasingly jeopardized both human health and the environment. In response, a unique electron-rich pyrazine-cored fluorescent covalent organic framework (COF) nanosheet, named as COF-TMP, was synthesized using an alkali-catalyzed reaction between 2, 3, 5, 6-tetramethylpyrazine (TMP) and terephthalaldehyde (TPA). Characterization demonstrated that COF-TMP boasted high porosity, pronounced fluorescence, and an abundance of (E)-2-styrylpyrazine (SPA) groups. These attributes render it an exceptional fluorescent sensor for the ultrahigh sensitivity detection of electron-deficient ROX molecules. The limit of detection (LOD) for COF-TMP in detecting ROX was found to be 0.015 ppb through fluorescence-quenching titration experiments-surpassing all previously reported fluorescent sensors. A combination of experimental results and theoretical calculations suggests that the extraordinary detection capability of COF-TMP for ROX arises from a static quenching mechanism. This study paves the way not only for a novel pyrazine-based fluorescent COF nanosheet with high porosity, exceptional fluorescent capabilities, and abundant SPA groups suitable for highly sensitive and selective ROX detection but also hints at its potential application as a fluorescent sensor for environmental pollution management and related domains.

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Covalent organic frameworks (COFs) are of massive interest due to their potential application spanning diverse fields such as gas storage and separation, catalysis, drug delivery systems, sensing, and organic electronics. In view of their application-oriented quest, the field of electrochromism marked a significant stride with the reporting of the first electrochromic COF in 2019 [J. Am. Chem. Soc. 2019, 141, 19831-19838]. Since then, new and novel COF structures with electrochromic features (denoted as ecCOFs) have been searched continuously. Yet, only a handful of ecCOFs have been constructed to date. A closer look at these reports suggests that multielectrochromism (showing at least three redox color states) in a COF assembly has only been achieved once, manifested through three-state electrochromism [Angew. Chem. 2021, 133, 12606 - 1261]. Herein, we report four-state electrochromism in tris(4-aminophenyl)amine-terephthalaldehyde (TAPA-PDA)-based COF constructed through the metal-catalyst free Schiff base approach. The four-state (orange, pear, green, and cyan) electrochromism demonstrated by the TAPA-PDA ecCOF opens several futuristic avenues for ecCOF's end use in flip-flop logic gates, intelligent windows, decorative displays, and energy-saving devices.

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Sp2-carbon (sp2-c) covalent organic frameworks (COFs), featuring distinctive π-conjugated network structures, facilitate the migration of photo-generated carriers, rendering them exceptionally appealing for applications in photoelectrochemical water splitting. However, owing to the powdery nature of COFs, leaving anchor the sp2-c COFs powder tightly onto a conductive substrate challenging. Here, we propose a method for preparing photoactive substance-conductive substrate integrated photocathodes through copper surface-mediated knoevenagel polycondensation (Cu-SMKP), this approach results in a uniform and stable sp2-c COF film, directly grown on commercial copper foam (COFTh-Cu). The COFTh-Cu demonstrates a high H2-evolution photocurrent density of 56 µA cm-2 at 0.3 V versus RHE, sustaining stability for 12 hours. The as-prepared COFTh-Cu represents a 4.5-fold increase in current density compared to traditional spin-coating methods and outperforms most COF photocathodes without cocatalysts. This innovative copper surface-mediated approach for preparing photocathodes opens up a crucial pathway towards the realization of highly active COF photocathodes.

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Ionic Covalent Organic Frameworks are a special subgroup that has risen as promising materials for innovative applications. In parallel, some of the so-called Reticular Innovative Organic compounds (RIOs), which are ionic and non-ionic porous materials have been used with great versatility, for several purposes. In this work, the ionic dye-based RIO-55 was chosen to capture a series of lanthanides (Eu, Gd, Dy, and Tb) from water, observing their affinity with the lattice and the performance of the adsorbent. Thus, the higher adsorbed amount was referred to as Eu3+ (Qmax = 370 mg/g), as well as the best affinity (KL = 5x10-3), following the Langmuir model. The impregnated Eu3+@RIO-55 was used for chemical sensing, capturing dopant molecules (ephedrine and dopamine) from water, showing great performance, even after some reuse cycles. In addition, some initial fluorescence tests were performed using RIO-55 and Eu3+@RIO-55 to observe the spectrum before and after lanthanide impregnation.

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Enzyme-free single-molecule sequencing has the potential to significantly expand the application of nanopore technology to DNA, proteins, and saccharides. Despite their advantages over biological nanopores and natural suitability for enzyme-free single-molecule sequencing, conventional solid-state nanopores have not yet achieved single-molecule DNA sequencing. The biggest challenge for the accuracy of single-molecule sequencing using solid-state nanopores lies in the precise control of the pore size and conformity. In this study, we fabricated nanopore devices by covering the tip of a quartz nanopipette with ultrathin two-dimensional (2D) covalent organic framework (COF) nanosheets (pore size ≈ 1.1 nm). The size of the periodically arranged nanopores in COF is comparable to that of protein nanopores, and the structure of each COF nanopore is consistent at the atomic scale. The COF nanopore device could roughly distinguish dAMP, dCMP, dGMP, and dTMP. Furthermore, a certain percentage of the current blockades originating from 150 nucleotides model DNA molecules (13.5% for dA50dC50dA50 and 11.1% for dC50dA50dC50) show distinct DNA sequence-specific concave and convex resistive current patterns. The finite element simulation confirmed that the current blockade pattern of a DNA molecule passing through a COF nanopore is dependent on the relative location of the nanopore with respect to the wall of the nanopipette. Our study is a significant step toward single-molecule DNA sequencing by solid-state nanopores.

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The reliable detection of organophosphorus pesticides (OPs) in complex matrices remains an enormous challenge due to inevitable interference of sample matrices and testing factors. To address this issue, we designed a nanozyme-coated mesoporous COF with guest molecule loading, and successfully used it to construct a dual-ratio dual-mode sensor through target-regulated signal generation. The multifunctional COF-based composite (MB/COF@MnO2, MCM) featured high loading of methylene blue (MB), oxidase-like MnO2 coatings as gatekeepers, and specific recognition of thiocholine (TCh). TCh, a regulator produced from acetylcholinesterase (AChE)-catalyzed hydrolysis of acetylthiocholine, could decompose MnO2 coatings, triggering the release of abundant MB and oxidation of few o-phenylenediamine (OPD). OPs, strong inhibitors of AChE, could restrain TCh production and MnO2 decomposition, thereby controlling the release of less MB and oxidation of more OPD. This regulation boosted the dual-ratio dual-mode assay of OPs by using the released MB and oxidized OPD in the solution as testing signals, measured by both fluorescent and electrochemical methods. Experimental results demonstrated the sensitive detection of dichlorvos with LODs of 0.083 and 0.026 ng/mL via the fluorescent/electrochemical mode, respectively. This study represented a creative endeavor to develop dual-ratio dual-mode sensors for OPs detection in complex samples, offering high sensitivity, excellent selectivity, and good reliability.

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A critical consideration in the application of phytoremediation to remediate sludge soil contaminated with heavy metals is the potential for leaching risks that prevail prior to the efficient uptake of these metals by plants. The most cost-effective method is to use heavy metal stabilizers with selective adsorption. A novel amide-based COF material (COF-TH) has been synthesized as a heavy metal stabilizer for Pb. COF-TH exhibits significant selectivity for Pb in five-metal-mixed solutions, with a distribution coefficient KD as high as 3279 mL·g-1, which was more than 7.3 times that of other heavy metals. The maximum adsorption capacity of COF-TH for Pb was 189 mg·g-1. The adsorption fitted Langmuir model and intra-particle diffusion model, and satisfied pseudo-second-order kinetic model. The excellent selectivity and adsorption performance originate from the complexation between abundant amide groups and Pb ions. Pot experiments and leaching assays confirm that COF-TH decreased Pb leachate concentrations by 77.8 % without significantly decreasing total phytoextracted amounts of other heavy metals, due to the high selectivity of COF-TH to Pb. Additionally, its positive impact on plant growth and microbial diversity makes it a promising soil remediation agent. This investigation offers a novel approach to mitigate the leaching risk of a specific heavy metal Pb during sludge land application by integrating soil phytoremediation with stabilization techniques.

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HYPOTHESIS: Hexavalent chromium, recognized as one of the most toxic heavy metals, demands the development of advanced materials capable of both adsorption and photocatalysis for effective Cr (VI) removal. EXPERIMENTS: This study successfully synthesized a two-dimensional zinc porphyrin covalent organic framework (ZnPor-COF) via a solvent-based method. Performance evaluations have demonstrated that the ZnPor-COF possesses outstanding capabilities for the adsorptive and/or photocatalytic elimination of Cr (VI). Particularly noteworthy is the observation that when adsorption and photocatalysis are coupled, the ZnPor-COF attains an exceptional 99.7 % removal rate for a Cr (VI) concentration of 30 mg/L within just 60 min, with minimal susceptibility to coexisting ions. After five consecutive cycles, the material sustains a removal efficiency of 90 %, indicative of its robust cyclability. FINDINGS: Theoretical calculations, as well as experimental validations, have indicated that the integration of Zn ions into the porphyrin COF not only results in an expanded specific surface area and an increased count of adsorption sites but also significantly improves the COF's photosensitivity and the capability for charge carrier separation. Furthermore, the core of the synergistic effect between adsorption and photocatalysis lies in the ability of photocatalysis to substantially augment the adsorption process.

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In this work, a composite hydrogel material consisting of chitosan-based composite hydrogel was prepared by a simple and rapid synthetic method and will be named three-dimensional (3D)-IL-COF-1@CS hydrogel. Possessing a stable 3D network structure and outstanding hydrophilicity, the novel hydrogel is capable of capturing glycopeptides. The 3D-IL-COF-1@CS hydrogel showed good sensitivity (0.1 fmol/µL) and selectivity (1:2000). In addition, 19 glycopeptides were captured in standard samples. In the analysis of human serum, 148 glycopeptides assigned to 72 glycoproteins were assayed in the serum of normal individuals, and 245 glycopeptides corresponding to 100 glycoproteins were found in the serum of colorectal cancer (CRC) patients. More importantly, several functional programs based on Gene Ontology analysis supported molecular biological processes that may be relevant to the pathogenesis of CRC, including aging, fibrinogen complex, and arylesterase activity. The low cost, simplicity, rapid synthesis, and good enrichment performance have a great future in glycoproteomics analysis and related diseases.

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The conventional covalent organic framework (COF)-based electrolytes with tailored ionic conducting behaviors are typically fabricated in the powder morphology, requiring further compaction procedures to operate as solid electrolyte tablets, which hinders the large-scale manufacturing of COF materials. In this study, we present a feasible electrospinning strategy to prepare scalable, self-supporting COF membranes (COMs) that feature a rigid COF skeleton bonded with flexible, lithiophilic polyethylene glycol (PEG) chains, forming an ion conduction network for Li⁺ transport. The resulting PEG-COM electrolytes exhibit enhanced dendrite inhibition and high ionic conductivity of 0.153 mS cm⁻¹ at 30 °C. The improved Li⁺ conduction in PEG-COM electrolytes stems from the loose ion pairing in the structure and the production of higher free Li⁺ content, as confirmed by solid-state 7Li NMR experiments. These changes in the local microenvironment of Li⁺ facilitate its directional movement within the COM pores. Consequently, solid-state symmetrical Li|Li, Li|LFP, and pouch cells demonstrate excellent electrochemical performance at 60 °C. This strategy offers a universal approach for constructing scalable COM-based electrolytes, thereby broadening the practical applications of COFs in solid-state lithium metal batteries.

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In order to expand the applicability of materials and improve their performance, the combined use of different materials has increasingly been explored. Among these materials, inorganic-organic hybrid materials often exhibit properties superior to those of single materials. Covalent organic frameworks (COFs) are famous crystalline porous materials constructed by organic building blocks linked by covalent bonds. In recent years, the combination of COFs with other materials has shown interesting properties in diverse fields, and the composite materials of COFs and TiO2 have been investigated more and more. These two outstanding materials are combined through covalent bonding, physical mixing, and other methods and exhibit excellent performance in various fields, including photocatalysis, electrocatalysis, sensors, separation, and energy storage and conversion. In this Review, the current preparation methods and applications of COF-TiO2 hybrid materials are introduced in detail, and their future development and possible problems are discussed and prospected, which is of great significance for related research. It is believed that these interesting hybrid materials will show greater application value as research progresses.

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Woven covalent organic frameworks (COF) possess three dimensional frameworks with spatially isolated Cu(I) centers and have promising optoelectronic properties because of metal to ligand charge transfer (MLCT). However, despite their potential, woven COFs have not yet been investigated as photocatalysts. In this study, we developed a new woven COF, Cu-PhenBDA-COF, functionalized with diacetylene bonds. Cu-PhenBDA-COF was fully characterized, and the optoelectronic and photocatalytic properties were compared to previously reported Cu-COF-505. The diacetylene bonds of the linker positively impacted the optoelectronic properties of Cu-PhenBDA-COF and resulted in a narrower band gap and better charge separation efficiency. When the Cu(I) center was removed from both woven COFs, the absorption edge was blue shifted, resulting in a wider band gap, and there was a considerable decrease in the charge separation efficiency, underscoring the pivotal role of MLCT. This trend was reflected in the photocatalytic activity of the woven COFs toward the degradation of sulfamethoxazole in water, where the highest reaction rate constant (k app ) was recorded for the metallated diacetylene functionalized woven COF, Cu-PhenBDA-COF.

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A multifunctional COF@HOF (ETTA-DFP@TCBP-HOF) composite is prepared by adding red-fluorescent ETTA-DFP COF to the blue-fluorescent TCBP-HOF preparation system through molecular hydrogen bonding or π - π stacking interactions in situ one-pot synthesis. ETTA-DFP@TCBP-HOF is a multifunctional material for the quantitative detection and simultaneous adsorption of 4-nitrophenol (4-NP) and metamitron (MET) in aqueous solution. As a dual-emission fluorescent sensor, the ETTA-DFP@TCBP-HOF has both fluorescence of TCBP-HOF at 474 nm and ETTA-DFP COF at 592 nm, which shows a ratiometric response to 4-NP and MET with high selectivity, good sensitivity, good anti-interference performance and fast response. As a adsorbent, ETTA-DFP@TCBP-HOF displays rapid adsorption kinetics, and acceptable adsorption capacity for 4-NP and MET. In conclusion, this work constructs a novel multifunctional hybrid material with dual-emission center of HOF and COF, which can not only be used as a ratiometric fluorescent probe for detection, but also for removal of hazardous pollutants, suggesting a new strategy for environmental remediation and human health.

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Covalent organic frameworks (COFs) are an innovative class of crystalline porous polymers composed of light elements such as C, N, O, etc., linked by covalent bonds. The distinctive properties of COFs, including designable building blocks, large specific surface area, tunable pore size, abundant active sites, and remarkable stability, have led their widespread applications in electrocatalysis. In recent years, COF-based electrocatalysts have made remarkable progress in various electrocatalytic fields, including the hydrogen evolution reaction, oxygen evolution reaction, oxygen reduction reaction, nitrogen reduction reaction, nitrate reduction reaction, and carbon dioxide reduction reaction. This review begins with an introduction to the design and synthesis strategies employed for COF-based electrocatalysts. These strategies include heteroatom doping, metalation of COF and building monomers, encapsulation of active sites within COF pores, and the development of COF-based derived materials. Subsequently, a systematic overview of the recent advancements in the application of COF-based catalysts in electrocatalysis is presented. Finally, the review discusses the main challenges and outlines possible avenues for the future development of COF-based electrocatalysts.

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Recognition and separation of chiral isomers are of great importance in both industrial and biological applications. However, owing to identical molecular formulas and chemical properties of enantiomers, signal transduction and amplification are still two major challenges in chiral sensing. In this study, we developed an enantioselective device by integrating chiral covalent organic framework nanosheets (CONs) with nanochannels for sensitive identification and quantification of enantiomers. Using 3,4-dihydroxyphenylalanine (DOPA) as the model analyte, the as-prepared chiral nanofluidic device exhibits a remarkable chiral recognition ability to l-DOPA than d-DOPA. More importantly, due to the chelation of DOPA with Fe3+ ions, it can efficiently block the ion transport through channel and shield the channel surface charge, which will amplify the difference in the electrochemical response of l-DOPA and d-DOPA. Therefore, a sensitive chiral recognition can be achieved using the present nanofluidic device coupled using electrochemical amplification strategy. Notably, using this method, an ultra-low concentration of l-DOPA (as low as 0.21 pM) can be facilely and successfully detected with a linear range of 1 pM-10 µM. This study provides a reliable and sensitive approach for achieving highly selective detection of chiral molecules.

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Uranium is an essential nuclear material in civilian and military areas; however, its extensive application raises concerns about the potential safety issues in the fields of environmental protection and nuclear industry. In this study, we developed an Ag/Ag2O-COF (covalent-organic framework) composite SERS substrate to detect uranyl ions (UO22+) in environmental aqueous solutions. Herein, the strong SERS effect of uranyl adsorbed in Ag/Ag2O composite and the high adsorption efficiency of COF TpPa-1 were combined to realize the trace detection of uranyl ions. This method displayed a linear range of 10-8 mol L-1 to 10-6 mol L-1 with the detection limit of 8.9 × 10-10 mol L-1 for uranyl ions. Furthermore, common metal cations and oxo-ions hardly affected the SERS detection of uranyl, which is helpful for the trace analysis of uranyl in natural water samples. Although the proposed strategy is deployed for uranyl detection, the reusable and high-efficiency system may be expanded to trace detection of other substance with Raman activity.

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In NH3 capture technologies, the desorption process is usually driven by high temperature and low pressure (such as 150-200 °C under vacuum), which accounts for intensive energy consumption and CO2 emission. Developing light responsive adsorbent is promising in this regard but remains a great challenge. Here, we for the first time designed and synthesized a light responsive azophenol-containing covalent organic framework (COF), COF-HNU38, to address this challenge. We found that at 25 °C and 1.0 bar, the cis -COF exhibited a NH3 uptake capacity of 7.7 mmol g-1 and a NH3/N2 selectivity of 158. In the adsorbed NH3, about 29.0 % could be removed by vis-light irradiated cis-trans isomerization at 25 °C, and the remaining NH3 might be released at 25 °C under vacuum. Almost no decrease in adsorption capacity was observed after eight adsorption-desorption cycles. As such, an efficient NH3 capture and low energy release strategy was established thanks to the multiple hydrogen bond interactions (which are strong in total but weak in individuals) between NH3 and the smart COF, as well as the increased polarity and number of hydrogen bond sites after the trans-cis isomerization.

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OBJECTIVES: To evaluate the wear resistance of three additively manufactured dental crown materials (NextDent C&B MFH, Saremco print CROWNTEC and Bego VarseoSmile Crown) under two environmental conditions (dry and artificial saliva), two loads (49 N and 70 N) and two surface treatments (polished and glazed). METHODS: A total of 120 specimens were divided into 24 groups and tested for wear under two loads (49 N and 70 N), surface treatment (polished or glazed), and environment (dry or submerged in artificial saliva). All samples underwent reciprocating wear testing at 1 Hz using a wear simulator, replicating 48 months of In Vivo conditions with a stainless-steel ball as the antagonist. The coefficient of friction (CoF), surface roughness, volumetric and vertical wear loss were measured and statistically analysed. Confocal microscopy assessed the surface properties of crown materials and the antagonists. RESULTS: The NextDent material demonstrated the most homogenous wear, with relatively low vertical and volumetric loss across all groups (p < 0.004). NextDent and Bego materials performed similarly in artificial saliva regardless of the load type (p > 1.000). The CoF remained below 0.3 for all groups. All groups exhibited significant increases in surface roughness after testing, however, this did not correlate with an increase in the CoF. Confocal analysis revealed material deformities due to load and notable scratch marks on the stainless-steel antagonists. CONCLUSION: It was found that all investigated addtively manufactured materials can be suggested for provisional use. Both vertical loss and volumetric loss results should be included for material evaluation. CoF and surface roughness should be implemented into wear evaluation. CLINICAL SIGNIFICANCE: This study highlights the practical value of additively manufactured dental crown materials, particularly for provisional restorations. However, their extended use requires careful consideration of individual patient needs, emphasising the need for judicious clinical application evaluation.

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