Selective Ag(I) Binding, H2S Sensing, and White-Light Emission from an Easy-to-Make Porous Conjugated Polymer

Recent progress of covalent organic frameworks as attractive materials for solid-phase microextraction: A review

Solid-phase microextraction (SPME) is a green, environmentally friendly, and efficient technique for sample pre-treatment. Covalent organic frameworks (COFs), a class of porous materials formed by covalent bonds, have gained prominence owing to their remarkable attributes, including large specific surface area, tunable pore size, and robust thermal/chemical stability. These characteristics have made COFs highly appealing as potential coatings for SPME fiber over the past decades. In this review, various methods used to prepare SPME coatings based on COFs are presented. These methods encompass physical adhesion, sol-gel processes, in situ growth, and chemical cross-linking strategies. In addition, the applications of COF-based SPME coating fibers for the preconcentration of various targets in environmental, food, and biological samples are summarized. Moreover, not only their advantages but also the challenges they pose in practical applications are highlighted. By shedding light on these aspects, this review aims to contribute to the continued development and utilization of COF materials in the field of sample pretreatment.

Porous organic polymers (POPs) for environmental remediation

Modern global industrialization along with the ever-increasing growth of the population has resulted in continuous enhancement in the discharge and accumulation of various toxic and hazardous chemicals in the environment. These harmful pollutants, including toxic gases, inorganic heavy metal ions, anthropogenic waste, persistent organic pollutants, toxic dyes, pharmaceuticals, volatile organic compounds, etc., are destroying the ecological balance of the environment. Therefore, systematic monitoring and effective remediation of these toxic pollutants either by adsorptive removal or by catalytic degradation are of great significance. From this viewpoint, porous organic polymers (POPs), being two- or three-dimensional polymeric materials, constructed from small organic molecules connected with rigid covalent bonds have come forth as a promising platform toward various leading applications, especially for efficient environmental remediation. Their unique chemical and structural features including high stability, tunable pore functionalization, and large surface area have boosted the transformation of POPs into various macro-physical forms such as thick and thin-film membranes, which led to a new direction in advanced level pollutant removal, separation and catalytic degradation. In this review, our focus is to highlight the recent progress and achievements in the strategic design, synthesis, architectural-engineering and applications of POPs and their composite materials toward environmental remediation. Several strategies to improve the adsorption efficiency and catalytic degradation performance along with the in-depth interaction mechanism of POP-based materials have been systematically summarized. In addition, evolution of POPs from regular powder form application to rapid and more efficient size and chemo-selective, "real-time" applicable membrane-based application has been further highlighted. Finally, we put forward our perspective on the challenges and opportunities of these materials toward real-world implementation and future prospects in next generation remediation technology.

Processable Conjugated Microporous Polymer Gels and Monoliths: Fundamentals and Versatile Applications

Conjugated microporous polymers (CMPs) as a new type of conjugated polymers have attracted extensive attention in academia and industry because of the combination of microporous structure and π-electron conjugated structure. The construction and application of gels and monoliths based on CMPs constitute a fertile area of research, promising to provide solutions to complex environmental and energy issues. This review summarizes and objectively analyzes the latest advances in the construction and application of processable CMP gels and monoliths, linking the basic and enhanced properties to widespread applications. In this review, we open with a summary of the construction methods used to build CMP gels and monoliths and assess the feasibility of different preparation techniques and the advantages of the products. The CMP gels and monoliths with enhanced properties involving various special applications are then deliberated by highlighting relevant scientific literature and discussions. Finally, we present the issues and future of openness in the field, as well as come up with the major challenges hindering further development, to guide researchers in this field.

Facile synthesis of a triazine-based porous organic polymer containing thiophene units for effective loading and releasing of temozolomide

Suzuki cross-coupling reaction was employed to easily obtain a triazine-based porous organic polymer (2,4,6-tris(5-bromothiophene-2-yl)-1,3,5-triazine [TBrTh]–1,3,5-benzene-triyltriboronic acid pinacol ester [BTBPE]–covalent triazine framework [CTF]) containing thiophene units. The chemical structure of TBrTh–BTBPE–CTF was revealed by solid-state 13C NMR, Fourier-transform infrared, and X-ray photoelectron spectroscopy. TBrTh–BTBPE–CTF with an amorphous structure exhibited excellent thermal stability and intrinsic porosity (373 m2·g−1 of Brunauer–Emmett–Teller surface area). Consequently, temozolomide (TMZ) was used as an oral alkylating agent in melanoma treatment to explore the drug loading and releasing behavior of TBrTh–BTBPE–CTF as a result of the low cytotoxicity of thiophene-based polymers. The successful loading of TMZ within the polymeric structure was suggested by thermogravimetric analysis and N2 sorption isotherms. The release experiments were performed in phosphate-buffered saline at pH values of 5.5 and 7.4, exhibiting good controlled-release properties. These results suggest that the current porous organic polymer is expected to be a drug carrier for the delivery and release of TMZ.

Influence mechanisms of 2-amino-1,3,5-triazine-4,6-dithiol coating on adhesion properties of polybutylene terephthalate/aluminum interface in nano-injection molding

Four interfacial models, including the PBT-Al&P (Plane), PBT-Al&V (V-slot), PBT-ATD-Al&P (Plane), and PBT-ATD-Al&V (V-slot), were constructed. The molecular dynamics (MD) method was launched to study the interfacial interactions and bonding behaviors between heterogeneous interfaces in nano-injection molding. The influence mechanism of the 2-amino-1,3,5-triazine-4,6-dithiol (ATD) coating on adhesion properties of the PBT–Al interface was mainly explored. Results indicated that the nano-V-slot interface system exhibited a double-wall-slipping phenomenon, unlike the non-nano-interface (macroscale molding) one. In nano-V-slot interfacial models, although the ATD coating reduced the double-wall-slipping velocity, it also increased the polar bonding, thus strengthened a better anchoring connection in the PBT–ATD–Al interface. The addition of the ATD layer did not cause chemical bonding of the original PBT materials; the interlocking effect behavior occurred between them and only coexisted in the form of physical anchors. Whatever model it was, the ATD layer interface had significantly higher interface energy than the other one, which was formed solely by PBT and Al substrate. In nano-injection molding, when the ATD intermediate layer was added, the bonding behavior of the PBT–Al interface also changed from simple nonbonded rigid anchoring to the entanglement anchor between the PBT–ATD macrochains and the nonbonding connections between ATD-Al interfaces.

Porous organic polymers as a platform for sensing applications

Sensing analysis is significantly important for human health and environmental safety, and has gained increasing concern. As a promising material, porous organic polymers (POPs) have drawn widespread attention due to the availability of plentiful building blocks and their tunable structures, porosity and functions. Moreover, the permanent porous nature could provide a micro-environment to interact with guest molecules, rendering POPs attractive for application in the sensing field. In this review, we give a comprehensive overview of POPs as a platform for sensing applications. POP-based sensors are mainly divided into five categories, including fluorescence turn-on sensors, fluorescence turn-off sensors, ratiometric fluorescent sensors, colorimetric sensors and chemiresistive sensors, and their various sensing applications in detecting explosives, metal ions, anions, small molecules, biological molecules, pH changes, enantiomers, latent fingerprints and thermosensation are summarized. The different structure-based POPs and their corresponding synthetic strategies as well as the related sensing mechanisms mainly including energy transfer, donor-acceptor electron transfer, absorption competition quenching and inner filter effect are also involved in the discussion. Finally, the future outlook and perspective are addressed briefly.

Synthesis and Antiproliferative Activity of 2,4,6,7-Tetrasubstituted-2H-pyrazolo[4,3-c]pyridines

A library of 2,4,6,7-tetrasubstituted-2H-pyrazolo[4,3-c]pyridines was prepared from easily accessible 1-phenyl-3-(2-phenylethynyl)-1H-pyrazole-4-carbaldehyde via an iodine-mediated electrophilic cyclization of intermediate 4-(azidomethyl)-1-phenyl-3-(phenylethynyl)-1H-pyrazoles to 7-iodo-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridines followed by Suzuki cross-couplings with various boronic acids and alkylation reactions. The compounds were evaluated for their antiproliferative activity against K562, MV4-11, and MCF-7 cancer cell lines. The most potent compounds displayed low micromolar GI50 values. 4-(2,6-Diphenyl-2H-pyrazolo[4,3-c]pyridin-7-yl)phenol proved to be the most active, induced poly(ADP-ribose) polymerase 1 (PARP-1) cleavage, activated the initiator enzyme of apoptotic cascade caspase 9, induced a fragmentation of microtubule-associated protein 1-light chain 3 (LC3), and reduced the expression levels of proliferating cell nuclear antigen (PCNA). The obtained results suggest a complex action of 4-(2,6-diphenyl-2H-pyrazolo[4,3-c]pyridin-7-yl)phenol that combines antiproliferative effects with the induction of cell death. Moreover, investigations of the fluorescence properties of the final compounds revealed 7-(4-methoxyphenyl)-2,6-diphenyl-2H-pyrazolo[4,3-c]pyridine as the most potent pH indicator that enables both fluorescence intensity-based and ratiometric pH sensing.

Dual-functional porous MOFs with hierarchical guest encapsulation for room-temperature phosphorescence and white-light-emission

The development of optical materials with room temperature phosphorescence (RTP) and white light emission (WLEDs) is highly desirable and remains a challenging task. Herein, a porous metal-organic framework PCN-921 with a high quantum yield (Φ_F = 93.6%) was achieved. To make full use of the advantages of the high porosity of PCN-921, we hierarchically encapsulated different guest molecules coronene and rhodamine B (RhB) into the framework. Unsurprisingly, the hybrid material coronene@PCN-921 was obtained after in situ encapsulation of the guest coronene into the framework, and it exhibits obvious RTP behavior with a long phosphorescence lifetime of 62.5 ns. Subsequently, second guest RhB molecules were introduced after soaking in RhB solution and the material RhB@coronene@PCN-921 was achieved. Interestingly, it exhibits white light emission with the CIE coordinates of (0.29, 0.34), and can be used as a high performance WLED lamp. This is the first work on dual-functional hybrid dyes@MOFs with hierarchical guest encapsulation for RTP and white light emission, which suggests the potential applications of MOFs in multifunctional optical devices.

Imine bond transformation of a dynamic Sm(III) macrocycle-based chemosensor: The indirect approach for detecting cyanuric chloride

Herein, we report our strategy to develop the efficient chemosensor and real-time monitoring technique for cyanuric chloride (TCT) detection. A luminescent macrocyclic mononuclear Sm(III) complex Sm-2_k bearing with two dynamic imine bonds has been constructed via the template synthesis between dialdehyde H₂Q_k and matched diamine 1,2-bis(2-aminoethoxy)ethane. Sensing experiments reveal that complex Sm-2_k exhibits the turn-off fluorescent and colorimetric response for TCT in CH₃OH. It is especially encouraging that this optical sensing process is not only rapid within 60 s but also high-efficient in the presence of TCT analogues as well as sensitive with the low limit of detection (LOD, 1.74 μM) and wide linear sensing range. Mechanism studies demonstrate that TCT sensing is mainly based on the imine bond transformation of probe Sm-2_k, which is due to the increased acidity induced by TCT. Meanwhile, a smartphone-based analytical method was developed to make complex Sm-2_k accessible for the real-time TCT detection by RGB value outputs. It is believed that this work can shed some constructive lights on design of chemosensors and convenient detection technique for highly reactive analytes.

A red luminescent Eu3+ doped conjugated microporous polymer for highly sensitive and selective detection of aluminum ions

A Eu³⁺ doped-CMP composite can be used as a chemosensor for highly sensitive and selective detection of Al³⁺.

A tetraphenylethylene-based covalent organic framework for waste gas adsorption and highly selective detection of Fe3+

A tetraphenylethylene-based covalent organic framework shows an outstanding performance for waste gas adsorption and has good selectivity and detection effect for Fe3+.

Halogenated Terephthalic Acid "Antenna Effects" in Lanthanide-SURMOF Thin Films

Lanthanide-based crystalline coatings have a great potential for energy-conversion devices, but until now luminescent surface-anchored materials were difficult to fabricate. Thin films, called lanthanides surface-mounted metal-organic frameworks (SURMOFs) with tetrasubstituted halide (fluorine, chlorine, and bromine) terephthalic acid derivative linkers as a basic platform for optical devices, exhibit a high quantum yield of fluorescence visible to the naked eyes under ambient light. We show that we can tune the luminescent properties in thin films by halide substitution, which affords control over the molecular structure of the material. We rationalize the mechanism for the modulation of the photophysical properties by "antenna effect", which controls the energy transfer and quantum yields using experimental and theoretical techniques for chelated lanthanides as a function of the type of atom substitutions at the phenyl rings and the resulting dihedral angle between phenyl rings in the linkers and carboxylate groups.

Conjugated porous polymers: incredibly versatile materials with far-reaching applications

This review discusses conjugated porous polymers and focuses on relating design principles and synthetic methods to key properties and applications such as (photo)catalysis, gas storage, chemical sensing, energy storage and environmental remediation.

The influences of the structure of thiophene-based conjugated microporous polymers on the fluorescence sensing properties

Three thiophene-based conjugated microporous polymers (CMPs: TTPTh, DBTh, and TBTh) were prepared by Sonogashira–Hagihara cross-coupling polymerization, and their structures were characterized by FTIR, ss ¹³C NMR, and elemental analyses.

Synthesis of Porous Organic Polymer-Based Solid-Acid Catalysts for 5-Hydroxymethylfurfural Production from Fructose

Herein, we report the synthesis of nanoporous polytriphenylamine polymers (PPTPA) by a simple one-step oxidative polymerization pathway and the materials were sulfonated with chlorosulfonic acid to introduce acidic sulfonic groups to the polymers to form solid acid catalysts (SPPTPA). Magnetic properties were added to SPPTPA catalysts by depositing Fe3O4 nanoparticles to develop (FeSPPTPA) solid acid catalysts, for performing dehydration of fructose to 5-hydroxymethylfurfural (HMF), which is regarded as a sustainable source for liquid fuels and commodity chemicals. XRD, FTIR spectroscopy, SEM, TGA, and N2 sorption techniques were used to characterize synthesized materials. The FeSPPTPA80 nanocatalyst showed superior catalytic activities in comparison to other catalysts due to the nanorods that formed after sulfonation of the PPTPA polymeric material which gave the catalyst enough catalytic centers for dehydration reaction of fructose. The recyclability tests revealed that the magnetic solid acid catalysts could be reused for four consecutive catalytic runs, which made FeSPPTPA a potential nanocatalyst for production of HMF.

Smartphone Nanocolorimetric Determination of Hydrogen Sulfide in Biosamples after Silver-Gold Core-Shell Nanoprism-Based Headspace Single-Drop Microextraction

In this work, the sensitive detection of hydrogen sulfide (H₂S) was realized at low cost and high efficiency through the application of silver-gold core-shell nanoprism (Ag@Au-np) combined with headspace single-drop microextraction (HS-SDME). After SDME, smartphone nanocolorimetry (SNC), with the aid of a smartphone camera and color picker software, was used to detect and quantify the H₂S. The method took advantage of the inhibition of the ultraviolet-visible (UV-vis) signal caused by H₂S etching of the Ag@Au-np preadded to the SDME solvent to measure the H₂S concentration. The coating of the gold layer not only ensured the high stability of the nanomaterial but also enhanced the selectivity toward H₂S. The HS-SDME method was simple to process and required only a droplet of solvent for analysis to be realized. This HS-SDME-SCN approach exhibited a calibration graph linearity of between 0.1 and 100 μM and a limit of detection of 65 nM (relative standard deviations of N% ( n = 3) < 4.80). A comparison with UV-vis spectrophotometry was conducted. The practical applicability of HS-SDME-SNC was successfully demonstrated by determining H₂S in genuine biosamples (egg and milk).

Synthesis of thieno[2,3-b]quinoline and selenopheno[2,3-b]quinoline derivatives via iodocyclization reaction and a DFT mechanistic study

In this letter, we report the regioselective iodocyclization reaction of 3-alkynyl-2-(methylthio)quinolines and 3-alkynyl-2-(methylseleno)quinolines for the synthesis of thieno[2,3-b]quinoline and selenopheno[2,3-b]quinoline derivatives. Furthermore, by employing various palladium-catalyzed Sonogashira, Suzuki, and Heck reactions, the structural diversification of the resulting halide derivatives, which can act as the important intermediates for building other valuable compounds, was achieved. All compounds were fully characterized by the FT-IR, mass, ¹H NMR, and ¹³C NMR spectral data. Finally, the structure of the thieno[2,3-b]quinoline derivative was confirmed by X-ray crystallography. This methodology provided a novel pathway to access quinoline fused heterocycles via iodocyclization reaction. Furthermore, the reaction process was well elucidated by density functional theory calculations.

Iodine mediated in situ generation of R-Se–I: application towards the construction of pyrano[4,3-b]quinoline heterocycles and fluorescence properties

Iodine mediated in situ generation of R-Se–I and its application towards the construction of pyrano[4,3-b]quinolin-1-one derivatives.

Fluorescent conjugated microporous polymer based on perylene tetraanhydride bisimide for sensing o-nitrophenol

A novel conjugated microporous polymer based on perylene tetraanhydride bisimide (DP₂A₂) has been synthesized through Sonogashira-Hagihara cross-coupling polymerization of tetrabromo-substituted perylene tetraanhydride bisimide derivative (DPBr₂ABr₂) with 1,4-diethynylbenzene, whose Brunauer-Emmett-Teller (BET) specific surface area is about 378 m² g^-1. The fluorescence quenching behaviors of the DP₂A₂ were investigated. It is found that the DP₂A₂ shows high sensitivity and selectivity to tracing o-nitrophenol (o-NP) in THF with Ks_V constant of 2.00 × 10⁴ L mol^-1. The detection limit (LOD) is 1.50 × 10^-9 mol L^-1. The possible sensing mechanism for the luminescent quenching of DP₂A₂ towards o-NP exciting at 365 nm was considered the donor-acceptor electron transfer mechanism, which is a combined result from both dynamic (collisional) and static quenching. Moreover, the static quenching process is dominant for DP₂A₂.

A pillar-layered porous CoII-MOF with dual active sites for selective gas adsorption

A pillar-layered microporous MOF has been constructed from linear trimeric {Co₃(COO)₆} clusters as SBUs. It exhibits preferential selective uptake of C₂H₂/C₂H₄, C₂H₂/C₂H₆ and CO₂/N₂ owing to its dual active sites.

A covalent triazine-based framework from tetraphenylthiophene and 2,4,6-trichloro-1,3,5-triazine motifs for sensing o-nitrophenol and effective I2 uptake

A covalent triazine-based framework with a tetraphenylthiophene (TTPT) backbone was prepared by the AlCl₃ catalyzed Friedel–Crafts reaction of commercially available material 2,4,6-trichloro-1,3,5-triazine with tetraphenylthiophene in dichloromethane.

Bottom-Up Construction of Porous Organic Frameworks with Built-In TEMPO as a Cathode for Lithium-Sulfur Batteries

Two redox-active porous organic frameworks (POFs) with a built-in radical moiety (TEMPO) and hierarchical porous structures were synthesized through a facile bottom-up strategy and studied as cathode materials for lithium-sulfur (Li-S) batteries. The sulfur loading in these two POFs reached 61 %, benefitting from their large pore volumes. Owing to the highly dense docking sites of TEMPO, sulfur could be covalently immobilized within the porous networks and efficiently inhibit the shuttle effect, thereby significantly improving the cycling performance. The composites TPE-TEMPO-POF-S (TPE=tetraphenylethene) deliver a capacity in excess of 470 mAh g^-1 after 200 cycles with a coulombic efficiency of around 100 % at a current rate of 0.1 C. Furthermore, TEMPO-POFs with sulfur embedded showed excellent rate capability with limited capacity loss at rates of 0.1-1 C.

Carbazolic Porous Framework with Tetrahedral Core for Gas Uptake and Tandem Detection of Iodide and Mercury

A multifunctional carbazolic porous framework (Cz-TPM), with a tetrahedral core, has been synthesized by FeCl₃ oxidative coupling polymerization. The Brunauer-Emmett-Teller surface area of the obtained polymers reaches 713.2 m² g^-1. Gas adsorption isotherms show that Cz-TPM exhibits large carbon dioxide (97.9 mg g^-1, 9.8 wt %, 273 K, and 1 bar) and hydrogen uptake capacities (149.3 cm³ g^-1, 1.34 wt %, 77 K, and 1 bar). Furthermore, Cz-TPM has been found to display tandem visual detection of iodide and mercury, respectively. The Cz-TPM dispersion turns to yellow in the presence of iodide salts and subsequently changes to nearly colorless on addition of Hg²⁺ salts that could be easily observed by the naked eye. Cz-TPM can detect I^- via "turn off" fluorescence quenching, and then the in situ generated Cz-TPM@I complexes can recognize Hg²⁺ ions via "turn on" fluorescence recovery. More importantly, Cz-TPM is stable over common solvents and can be easily recovered by excessive water washing and centrifugation for further repeated use. As far as we know, carbazolic porous organic frameworks enabling detection of I^- and Hg²⁺ have not been reported.

Single-component small-molecule white light organic phosphors

A family of two small and easily synthesizable 1,2,3-triazole molecules with intrinsic white-light-emission in the solid state has been reported. The white light is assigned to the supramolecular aggregate emission (SAE) that is unusual for single-component white light phosphors.

A soluble conjugated porous organic polymer: efficient white light emission in solution, nanoparticles, gel and transparent thin film

A multifunctional, solution processable, ultramicroporous polymer employed for white light emission in solution, nanoparticles, a gel and a transparent thin film.

Subphthalocyanine-based porous organic polymers

The synthesis and photophysical properties of two subphthalocyanine-based porous organic polymers (SubPc-POPs) are reported.

Circularly polarized luminescence based chirality transfer of the chiral BINOL moiety via rigid π-conjugation chain backbone structures

Three kinds of chiral BINOL-based polymers could be synthesized by polymerization in a Pd-catalyzed cross-coupling reaction.

Turn-on and Ratiometric Luminescent Sensing of Hydrogen Sulfide Based on Metal-Organic Frameworks

The sensing of hydrogen sulfide (H₂S) has become a long-time challenging task. In this work, we developed a general strategy for sensing of H₂S utilizing postsynthetic modification of a nano metal-organic frameworks (MOF) UiO-66-(COOH)₂ with Eu³⁺ and Cu²⁺ ions. The nano MOF Eu³⁺/Cu²⁺@UiO-66-(COOH)₂ displays the characteristic Eu³⁺ sharp emissions and the broad ligand-centered (LC) emission simultaneously. Because H₂S can strongly increase the fluorescence of Eu³⁺ and quench the broad LC emission through its superior affinity for Cu²⁺ ions, the MOF Eu³⁺/Cu²⁺@UiO-66-(COOH)₂ exhibits highly sensitive turn-on sensing of H₂S over other environmentally and biologically relevant species under physiological conditions. Furthermore, this approach for fluorescent turn-on sensing of H₂S is expected to extend to other water-stable MOFs containing uncoordinated -COOH.