Luminescent Covalent Organic Frameworks Research Articles

A dual-signal triple-readout optical sensing platform for α-glucosidase and β-glucosidase activity monitoring and inhibitor screening based on luminescent covalent organic framework

BackgroundAs promising biomarkers of diabetes, α-glucosidase (α-Glu) and β-glucosidase (β-Glu) play a crucial role in the diagnosis and management of diseases. However, there is a scarcity of techniques available for simultaneously and sensitively detecting both enzymes. What's more, most of the approaches for detecting α-Glu and β-Glu rely on a single-mode readout, which can be affected by multiple factors leading to inaccurate results. Hence, the simultaneous detection of the activity levels of both enzymes in a single sample utilizing multiple-readout sensing approaches is highly attractive. ResultsIn this work, we constructed a facile sensing platform for the simultaneous determination of α-Glu and β-Glu by utilizing a luminescent covalent organic framework (COF) as a fluorescent indicator. The enzymatic hydrolysis product common to both enzymes, p-nitrophenol (PNP), was found to affect the fluorometric signal through an inner filter effect on COF, enhance the colorimetric response by intensifying the absorption peak at 400 nm, and induce changes in RGB values when analyzed using a smartphone-based color recognition application. By combining fluorometric/colorimetric measurements with smartphone-assisted RGB mode, we achieved sensitive and accurate quantification of α-Glu and β-Glu. The limits of detection for α-Glu were determined to be 0.8, 1.22, and 1.85 U/L, respectively. Similarly, the limits of detection for β-Glu were 0.16, 0.42, and 0.53 U/L, respectively. SignificanceApplication of the proposed sensing platform to clinical serum samples revealed significant differences in the two enzymes between healthy people and diabetic patients. Additionally, the proposed sensing method was successfully applied for the screening of α-Glu inhibitors and β-Glu inhibitors, demonstrating its viability and prospective applications in the clinical management of diabetes as well as the discovery of antidiabetic medications.

Strategic design of a rare trigonal symmetric luminescent covalent organic framework by linker modification

We designed a trigonal symmetric imine-linked covalent organic framework (COF), TFPC-DAB, with control over the angularity of the building units, where a bent C2-symmetric diamine, such as 1,3-diaminobenzene (1,3-DAB or DAB), with an exo-angle of 120° was used instead of those with an exo-angle of 180°, in combination with a C3-symmetric trialdehyde, such as tri(4-formylphenoxy)cyanurate (TFPC). Its synthesis was accomplished by reacting the building units in a mixture of mesitylene/dioxane/6 M acetic acid under solvothermal conditions. The phase purity, thermal stability, and porosity of TFPC-DAB were established by various analytical techniques. Utilizing the Density Functional Tight Binding (DFTB+) simulation and Pawley refinement, the best fit of the small angle x-ray pattern was found to have an AA stacking of TFPC-DAB in the trigonal space group P3 with low refinement parameters. Such smart materials are in huge demand to detect hazardous corrosive chemicals, such as HCl and NH3. The dual features of electron deficient π-acidic triazine moiety and heteroatoms (N/O) from TFPC and electron rich phenyl units from DAB embodied in the framework enhance its luminescent property and thereby make it suitable for solvent-based HCl and NH3 sensing. The detection limits for HCl and NH3 in methanol were found to be 14 and 82 ppb, respectively. The effect of solvent polarity on the sensing studies was observed with much lower detection limits in dioxane: 2.5 and 11 ppb for HCl and NH3, respectively. A detailed theoretical calculation using density functional theory and configurational bias Monte Carlo modules was conducted for understanding interactions between the COF and HCl or NH3 analytes.

A Stimuli-Responsive Dual-Emitting Covalent Organic Framework Shows Selective Sensing of Highly Corrosive Acidic Media via Fluorescence Turn-On Signal with White Light Emission.

Luminescent covalent organic frameworks (LCOFs) have been employed as platforms for sensing analytes. Judicial incorporation of appropriate functional units inside the framework leads to the different electronic states in the presence of external stimuli, e.g., temperature, pH, etc. We report herein a new COF (TPEPy) as a solid-state acid sensor specific for the highly acidic environments that range from pH ∼0.5 to ∼3.0. This COF shows a protonation-induced reversible color change from bright yellow to deep red upon decreasing the pH from 3 to 0.5 and vice versa. No visual color change was, however, observed above pH 3.0. Photoluminescence (PL) studies show that the intrinsic emission peak of the TPEPy COF at 530 nm is shifted to 420 nm owing to the N-protonation of the imine nitrogen of COF within this pH range. Extensive studies demonstrate that the protonation behavior of the COF is counterion dependent. This was revealed when different acids, e.g., HCl, HNO3, HBr, and HI, were employed. The intensity of the proton-induced emission peak at 420 nm depends significantly upon the counterions with the order of HCl > HNO3 > HBr > HI. These anions interact with the protonated TPEPy COF by cation-anion and H-bonding interactions. Further, the pristine COF showed near white light emission at a particular pH of 2.5 (CIE coordinates 0.27, 0.32). From the PL spectrophotometric titrations, the deprotonation pKa was experimentally found to be 1.8 ± 0.02 for the TPEPy COF. The sensor reported herein is reversible, reusable, and regenerable and is useful for assessing pH fluctuations within a strongly acidic range via digital signaling.

Mechanical interlocking induced emission in two-dimensional covalent organic frameworks

The development of two-dimensional (2D) solid-state luminescent covalent organic frameworks (COFs) remains an intriguing challenge due to the aggregation quenching caused by π-π interactions. In this study, a novel approach utilizing mechanical interlocking was employed to construct two 2D-COFs, namely mTPE-COF-1 and mTPE-COF-2. These COFs exhibited robust solid-state emissive properties. Fully characterization and spectroscopic analysis revealed that the regular interleaving mechanical restraints was able to mitigate the π-π stacking interactions in the two 2D-COFs. As a result, this inhibition inactivates non-radiation deactivation and turns on the luminescence. Theoretical calculations support the promotion of mechanical interlocking for emissions. Furthermore, by coating mTPE-COF-1 and mTPE-COF-2 onto a blue light-emitting diode, a high purity white light can be generated. This study offers a novel approach to design 2D luminescent COFs using mechanical interlocking strategy.

Hydrogen Isotope Effect Endows a Breakthrough in Photoluminescent Covalent Organic Frameworks.

Luminescent covalent organic frameworks (LCOFs) have emerged as indispensable candidates in various applications due to their greater tunable emitting properties and structural robustness compared to small molecule emitters. An unsolved issue in this area is developing highly luminescent LCOFs of which the nonradiative quenching pathways were suppressed as much as possible. Here, a robust aminal-linked COF (DD-COF) possessing perdeuterated light-emitting monomers was designed and synthesized. The solid-state photoluminescence quantum yield of the DD-COF reaches 81%, significantly outcompeting all state-of-the-art LCOFs reported so far. The exceptional luminescent efficiency is attributed to the inhibition of different pathways of nonradiative decay, especially from bond vibrations where only substitution by a heavier isotope with a lower zero-point vibration frequency works. Furthermore, the prepared deuterated COF not only boosts higher photostability under UV irradiation but also enables superior fluorescence sensing performance for iodine detection compared to nondeuterated COF.

Linker engineering to regulate fluorescence of 1,3,5-tris(phenylacetylene)benzene-based covalent organic frameworks for white light-emitting diodes and information encryption and decryption

Luminescent covalent organic frameworks (LCOFs) is a promising luminescent material with huge potential for various applications because it can integrate various chromophores into its porous ordered structure. A facile and effective approach to edit LCOFs emission is very necessary but remains a challenge. Herein, a rigidity-flexibility combination strategy to edit the luminescence properties of LCOFs was proposed by using a flexible fluorescent 1,3,5-tris(phenylacetylene) benzene with propeller-like conformation as center skeleton and linkers with different rigidity and conjugation degree. Since the conjugated degree of LCOFs’ frameworks depended on conformation of propeller-like 1,3,5-tris(phenylacetylene)benzene skeleton, the emission wavelengths of 1,3,5-tris (phenylacetylene)benzene-based LCOFs could be edited by linkers to tune conjugated degree of the frameworks. These 1,3,5-tris(phenylacetylene)benzene-based LCOFs emitted blue, green, yellow, orange and red light depending on the conjugation degree caused by the effect of the linkers of melem, terephthalic dihydrazide, hydrazine hydrate and p-phenylenediamine on the conformation of central skeleton. Binary or ternary mixed 1,3,5-tris(phenylacetylene)benzene-based LCOFs were used for white emission, white light-emitting diodes and information encryption/decryption. The work provides a simple yet efficient method to systematically edit the emission behaviors of LCOFs by linker engineering.

A fully π-conjugated triazine-based 2D covalent organic framework used as metal-free yellow phosphors in white light-emitting diodes

Luminescent covalent organic frameworks (COFs) can be used as metal-free phosphors to replace rare earth-based phosphors for LEDs. Here, a fully π-conjugated 2D COF containing triazine units is synthesized via Knoevenagel condensation by using terephthalaldehyde (TPA) and 2,2′,2′'-((1,3,5-triazine-2,4,6-triyl)tris([1′',1′''-biphenyl]-4′,4′'-diyl))triacetonitrile (TTTA) as monomers. This yellow-emitting COF consists of a periodic hexagonal pore structure and is in an eclipsed (AA) stacking mode. Its solid-state photoluminescence quantum yield (PLQY) is 26.0 %, its thermal decomposition temperature (Td) is ca. 495 °C, and its relative emission intensity at 90 ℃ is 80.0 % of that at 30 °C, at 150 ℃ is 58.9 % of that at 30 °C. Together with GaN-based blue-emitting chips (λem,max ≈ 460 nm, around 25.0 lm·W−1), a series of cold/neutral/warm white LEDs are fabricated by using the COF as yellow phosphors at different concentrations in epoxy resin. At 2.0 wt%, a cold white LED is obtained with the best performances, its correlated color temperature (CCT) is 5743 K, color rendering index (CRI) is 83.1, Commission Internationale de L’Eclairage (CIE) chromaticity coordinate is (0.33, 0.29), luminous efficacy (LE) is 18.18 lm·W−1.

High-precision luminescent covalent organic frameworks with sp2-carbon connection for visual detecting of nereistoxin-related insecticide

A new strategy for nereistoxin-related insecticide, cartap, detection in foodstuff and the environment is of great importance due to its poisoning of human beings through direct exposure or via biomagnification. Herein, a highly planar conjugated sp2 carbon-connected COF (F-Csp2-TT) was synthesized via Knoevenagel condensation reaction followed by the post-modification to develop a new platform for cartap visual detection in agricultural and food samples. The synergistic effect of highly planar conjugation and dense functional groups in the opened framework endowed F-Csp2-TT with a high-precision luminescence sensing performance. Meanwhile, the exquisitely designed F-Csp2-TT presented robust chemical stability, radiation stability, and good reproducibility. Benefiting from these advantages, high-precision luminescent F-Csp2-TT achieves a low detection limit of 0.51 μg/L to cartap over the range of 1–300 μg/L (R2=0.9938), and the recoveries percentage in food products was calculated as 95.90%− 119.3%. More significantly, the smartphone-based high-precision platform by F-Csp2-TT was established and successfully applied to portable monitoring of cartap and water content. Therefore, our work revealed the enormous potential of Csp2-connected COF, which opened a new situation for insecticide detection.

A three-dimensional luminescent covalent organic framework for rapid, selective, and reversible uranium detection and extraction

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 UO22+ 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.

A luminescent covalent organic framework with recognition traps for nitro-pesticides detection, pH sensing and metal ions identification

Special recognition sites in luminescent covalent organic frameworks (LCOFs) are extremely important to improve the selectivity of detection. Herein, we report on a novel LCOF named TFBD-Py-COF with three-in-one recognition traps composed of hydrogen bonding, reversible protonation of N and O–H⋯NC chelating unit. TFBD-Py-COF is synthesized via 3,3′,5,5′-tetraformyl-4,4′biphenyldiol (TFBD) and 4,4′,4″,4‴-(pyrene-1,3,6,8-tetrayl) tetra aniline (PyTTA), which has a two-dimensional dual rhombic pore structure based on AA stacking with the pore diameters of 0.88 and 1.38 nm. The hydroxyl group of TFBD-Py-COF can form hydrogen bonds with imines and induce the trans conformation of the mesoimine, as evidenced by the single crystal structure of the model compound. TFBD-Py-COF exhibits good chemical and thermal stability with a high BET surface area of 750 m2 g−1. TFBD-Py-COF shows visible fluorescent color from blue to green when dispersed in different organic solvents. TFBD-Py-COF has the fluorescence chemo-sensing ability for nitro-pesticides based on electron transfer-induced fluorescence quenching mechanism, allowing a high sensitivity and low detection limit of 4.0 × 10−2 ppm for p-nitroaniline. In addition, TFBD-Py-COF shows reversible acidochromic behaviors and concomitant distinct fluorescent color change due to the protonation of the imine N. Furthermore, the fluorescence of TFBD-Py-COF is selectively quenched by Fe3+ with a Ksv of 1.1 × 104 and a detection limit of 0.2 μM, owing to the coordination of Fe3+ with the O–H⋯NC chelating unit. This study demonstrates great potential of LCOFs for multifunctional detection.

Hydrazone-linked luminescent covalent organic frameworks based on AIE-active unit for acid vapour sensing

Many two-dimensional (2D) covalent organic frameworks (COFs) exhibit weak fluorescence in the solid state or relatively strong fluorescence only in their suspensions. So it is significant to develop a COF with high luminescence in its as-synthesized solid-state for the better practical applications such as fluorescence sensor. We constructed a 2D COF of TPE-DHZ-COF with the hydrazone bond as the linkage and the monomers of triphenylbenzene (TPE) units with aggregation-induced emission (AIE) characteristics, and also synthesized an analogue of TPB-DHZ-COF without AIE-active unit as a comparison. Compared with TPB-DHZ-COF, the COF with TPE unit show excellent solid-state luminescence properties, demonstrating that introducing of AIE-active unit in COF can significantly improve the solid-state luminescence performance of hydrazone-linked COFs. In addition, all of these COFs could weaken or quench their fluorescence when exposure to strong-acid vapour. We regarded the response of TPE-DHZ-COF to trifluoroacetic acid (TFA) vapour as the research object, and found that TPE-DHZ-COF exhibited a fast response speed, strong adsorption capacity, excellent stability and recycling performance in the detection of TFA vapour. These results indicated that COFs would be a good candidate in solid-state fluorescence sensing.

Functionalized luminescent covalent organic frameworks hybrid material as smart nose for the diagnosis of Huanglongbing

Quantitative identification of several volatile organic compounds (VOCs) associated with the same disease provides a strong guarantee of the accurate analysis of the disease. Designing a single luminescent material to interact differently with multiple analytes can generate response patterns with remarkable diversity. Here, a highly green luminescent imine-based 2D COF (TtDFP) is designed and synthesized. TtDFP has ultrasensitive detection performance for trace water in organic solvent. Constructing a ratiometric fluorescence sensor can improve sensitivity for detecting analytes. To contrast the fluorescence signals of Eu3+ and COFs in sensing assays, a simple postsynthetic modification (PSM) method is used to introduce Eu3+ into TtDFP. The obtained red luminescent hybrid material Eu3+@TtDFP EVA film can be a fluorescent nose capable of "sniffing out" and quantifying VOCs (GA and PhA) associated with Huanglongbing (HLB, a devastating disease of citrus) at ppb levels. This work provides a technique of developing functionalized COF hybrid material to facilitate the distinction of various VOCs, which can also be extended to monitor the levels of other VOCs relevant to human health.

Luminescent Covalent Organic Frameworks for Biosensing and Bioimaging Applications.

Luminescent covalent organic frameworks (LCOFs) have attracted significant attention due to their tunability of structures and photophysical properties at molecular level. LCOFs are built to highly ordered and periodic 2D or 3D framework structures through covalently assembling with various luminophore building blocks. Recently, the advantages of LCOFs including predesigned properties of structure, unique photoluminescence, hypotoxicity and good biocompatibility and tumor penetration, broaden their applications in biorelated fields, such as biosensing, bioimaging, and drug delivery. A specific review that analyses the advances of LCOFs in the field of biosensing and bioimaging is thus urged to emerge. Here the construction of LCOFs is reviewed first. The synthetic chemistry of LCOFs highlights the key role of chemical linkages, which not only concrete the building blocks but also affect the optical properties and even can act as the responsive sites for potential sensing applications. How to brighten LCOFs are clarified through description of structure managements. The ability to utilize the luminescence of LCOFs for applications in biosensing and bioimaging is discussed using state-of-the-art examples of varied practical goals. A prospect finally addresses opportunities and challenges the development of LCOFs facing from chemistry, physics to the applications, according to their current progress.

Deuterated Covalent Organic Frameworks with Significantly Enhanced Luminescence.

Luminescent covalent organic frameworks (COFs) find promising applications in chemical sensing, photocatalysis, and optoelectronic devices, however, the majority of COFs are non or weakly emissive owing to the aggregation-caused quenching (ACQ) or the molecular thermal motion-based energy dissipation. Here, we report a previously unperceived approach to improve luminescence performance of COFs by introducing isotope effect, which is achieved through substitution of hydrogen from high-frequency oscillators X-H (X=O, N, C) by heavier isotope deuterium. Combining the "bottom-up" and in situ deuteration methods generates the first deuterated COF, which exhibits an impressively 19-fold enhancement in quantum yield over that of the non-deuterated counterpart. These results are interpreted by theoretical calculations as the consequence of slower C/N-D and OD⋅⋅⋅O vibrations that impede the nonradiative deactivation process. The proposed strategy is proved applicable to many other types of emissive COFs.

Dual‐Function Fluorescent Covalent Organic Frameworks: HCl Sensing and Photocatalytic H2 Evolution from Water

AbstractTwo ultrastable luminescent covalent organic frameworks (COFs), PyTA‐BC and PyTA‐BC‐Ph, are synthesized through polycondensations of 4,4′,4″,4′″‐pyrene‐1,3,6,8‐tetrayl)tetraaniline (PyTA‐4NH2) with two carbazole‐based derivatives having different degrees of conjugation. The PyTA‐BC and PyTA‐BC‐Ph COFs exhibit ultrahigh thermal stabilities (up to 421 °C), excellent crystallinity, and high Brunauer–Emmett–Teller surface areas (up to 1445 m2 g−1). These COFs display strong fluorescence emissions in various solvents, with their emission maxima gradually red‐shifting upon increasing the polarity of the solvent (solvatochromism). Upon exposure to HCl, they respond very rapidly and sensitively in terms of changing their colors and fluorescence emission maxima. In the presence of a sacrificial electron donor, these COFs mediate the highly efficient photocatalytic evolution of H2 from water. In the absence of a noble metal cocatalyst, the COFs and ascorbic acid provide a photocatalytic H2 production of up to 1183 µmol g−1 h−1 (λ ≥ 420 nm); this value is the highest reported to date for a COF. Such COFs appear to be potentially useful as chemosensors for the naked‐eye and sensitive spectroscopic detection of HCl and as cocatalysts for the sustainable photocatalytic production of H2 from water.

Comprehensive Structural and Microscopic Characterization of an Azine-Triazine-Functionalized Highly Crystalline Covalent Organic Framework and Its Selective Detection of Dichloran and 4-Nitroaniline.

In recent years, luminescent covalent organic frameworks (COFs) constructed with nitrogen-rich building units have been the target for selective detection of electron-deficient pollutants to serve for a clean environment. In order to contribute to these imperative applications, an azine-triazine-based COF (ANCOF) has been solvothermally synthesized and structurally characterized by a variety of analytical methods for comprehensive studies. ANCOF possesses micropores with a rare ABAB stacking, high thermal and chemical stabilities, and a Brunauer-Emmett-Teller surface area of 565 m2 g-1. On the other hand, ANCOF exhibits excellent luminescent property in the presence of different solvents marked by the wavelength shift due to polarity. Exploiting the bluish-white emission of ANCOF in aqueous medium, it has been found to be an excellent probe for the discriminative and selective detection of dichloran (DCNA) and 4-nitroaniline (4-NA) with detection limits of 142 and 89 ppb, respectively. A distinguishable color change for DCNA and 4-NA has been reflected by UV illumination, fluorescence microscopy, and a handy paper strip method. Time-resolved fluorescence studies, spectral overlap, density functional theory, and configurational bias Monte Carlo molecular simulation have been utilized to understand the mechanism of action and interaction of DCNA and 4-NA with the host ANCOF. The selectivity of ANCOF toward DCNA and 4-NA in the presence of other analytes and the recyclability after sensing experiments have been successfully demonstrated. Furthermore, the stability of ANCOF has been confirmed by powder X-ray diffraction and field emission scanning electron microscopy with good retention of crystallinity and morphology. To the best of our knowledge, this is the first COF employed for the detection of amine derivatives in aqueous solution combining both experimental and computational studies.

Smart Responsive Luminescent Aptamer-Functionalized Covalent Organic Framework Hydrogel for High-Resolution Visualization and Security Protection of Latent Fingerprints.

Covalent organic frameworks (COFs) have been proposed as alternative candidates for "smart" materials due to their ordered π-columnar structures. However, it remains a challenge to develop external-stimuli-responsive luminescent COFs for confidential information protection. Here, we have designed and synthesized a water-dispersible and smart responsive luminescent carboxymethyl cellulose-COF hydrogel encapsulated 5-(dimethylamino)-N,N-bis (pyridin-2-ylmethyl) napthalene-1-sulfonamide, named CMC-COF-LZU1⊃DPYNS, for latent fingerprint imaging and encryption. We show that the fluorescence of CMC-COF-LZU1⊃DPYNS is reversibly switchable upon addition of Cu2+/H2O. This effect endows potential applications of tunable luminescent COFs based hydrogel as an invisible security probe for imaging, recording, storage, and security of latent fingerprint information. It is shown that the latent fingerprint information incubated by the aptamer-functionalized CMC-COF-LZU1⊃DPYNS hydrogel is invisible in the presence of Cu2+, but three levels of fingerprint features with high-resolution patterns could be readable upon addition of H2O under UV light. The design strategy provides a promising platform for the development of smart responsive luminescent COFs and their detection and protection of valuable latent fingerprint information.

LCOFs: Role of the excited state hydrogen bonding in the detection for nitro-explosives

It is of important theoretical significance to research the mechanism of luminescent covalent organic frameworks (LCOFs) for detecting nitro-explosives. The interaction between LCOF-BTT1 and nitrobenzene has been investigated by DFT and TDDFT methods. By studying electronic configurations and frontier molecular orbitals, the luminescence mechanism of LCOF-BTT1 has changed due to the hydrogen bonding formed between LCOF-BTT1 and nitrobenzene (Complex 1). Further study of electronic transition energies, hydrogen bond lengths, 1H NMR and IR spectra of Complex 1 reveals that hydrogen bonding is stronger in the excited state than in the ground state, indicating fluorescence quenching. Furthermore, the fluorescence rate coefficient and the internal conversion rate coefficient of Complex 1 are correspondingly decreased and increased, indicating that the increase in the strength of hydrogen bonding in the excited state is beneficial to the non-radiative transition and is not conducive to the radiation transition.

Improving Covalent Organic Frameworks Fluorescence by Triethylamine Pinpoint Surgery as Selective Biomarker Sensor for Diabetes Mellitus Diagnosis.

The nitrogen-containing imine or hydrazone linked covalent organic frameworks (COFs) are poorly luminescent due to the fluorescence quenching by nitrogen atoms in the linkages, even if highly luminescent units and linkers are employed. The fluorescence quenching pathway to prevent linkage-originated to mitigate the inherent limitations of the linkage is a promising method for luminescent COFs. The generation of N- by deprotonation of the N-H unit eliminates the electron transfer from N lone pair to COF (TpPa-1) and enhances the luminescence. In this work, TpPa-1 achieved turn-on luminescence response with good sensitivity and reproducibility toward triethylamine (TEA) vapor in the process of deprotonation. The fabricated detector offers a viable approach for sensing ppm-level TEA, which can remind people to take timely measures to reduce the environmental hazards caused by TEA. The fluorescent sensor TpPa-1@LE constructed by the products of TpPa-1 and TEA can quantitatively trace biomarker methylglyoxal (MGO) for diabetes mellitus diagnosis in serum system. Furthermore, using TEA and MGO as input signals and the two fluorescence emissions G476 and Y525 as output signals, an advanced analytical device based on two Boolean logic gates with INH and AND function is constructed. This work provides a new strategy for improving the weak luminescence of COF in aqueous solution and realizes selective response to biomarker (MGO) for diabetes mellitus diagnosis.

TD-DFT insights into the sensing potential of the luminescent covalent organic framework for indoor pollutant formaldehyde.

This paper investigates the sensitivity of the luminescent thieno[2,3-b]thiophene-based covalent organic framework (TT-COF) towards the formaldehyde using the density functional theory and time-dependent method. The hydrogen bonding dynamics is explored by comparison of geometries, electronic transition energies, binding energies, UV-vis, and infrared spectra. Frontier molecular orbitals examination, natural population analysis, and plotted electron density difference map describe the quenching process explicitly via electron density distribution. The MOMAP program illuminates the quenching owing to TT-COF-HCHO complex radiative rate constant. Furthermore, the S1-T1 energy gap describes the facilitation of the luminescence quenching through the intersystem crossing. Above all results elaborate the TT-COF's potential to detect the formaldehyde.