Covalent Organic Polymer Research Articles

Cationic Covalent Organic Polymer Thin Film for Label-free Electrochemical Bacterial Cell Detection.

Numerous species of bacteria pose a serious threat to human health and cause several million deaths annually. It is therefore essential to have quick, efficient, and easily operable methods of bacterial cell detection. Herein, we synthesize a novel cationic covalent organic polymer (COP) named CATN through the Menshutkin reaction and evaluate its potential as an impedance sensor for Escherichia coli cells. On account of its positive surface charge (ζ-potential = +21.0 mV) and pyridinium moieties, CATN is expected to interact favorably with bacteria that possess a negatively charged cell surface through electrostatic interactions. The interdigitated electrode arrays were coated with CATN using a simple yet non-traditional method of electrophoresis and then used in two-electrode electrochemical impedance spectroscopy (EIS) measurements. The impedance response showed a linear relationship with the increasing concentration of E. coli. The system was sensitive to bacterial concentrations as low as ∼30 CFU mL–1, which is far below the concentration considered to cause illnesses. The calculated limit of detection was as low as 2 CFU mL–1. This work is a rare example of a COP used in this type of bacteria sensing and is anticipated to stimulate further interest in the synthesis of organic polymers for EIS-based sensors.

In situ generated PtNPs to enhance electrochemiluminescence of multifunctional nanoreactor COP T4VTP6 for AFB1 detection

Herein, a competitive quenching electrochemiluminescence immunosensor towards aflatoxin B1 (AFB1) detection was constructed by in-situ forming platinum nanoparticles (PtNPs) on ECL emitter COP T4VTP6 and effective ECL signal quencher Fc-CHO/Phe. In this system, cationic covalent organic polymer COP T4VTP6 emitted stronger cathode ECL signal at 765 nm, it acted as an interesting nanoreactor to immobilize PtCl62− through electrostatic adsorption, and directly in situ catalyzed the redox reaction to produce PtNPs without adding any external reducing agent, where PtNPs not only served as the substrate for antibody immobilization, but also played the role of coreaction accelerator to catalyze the production of SO4−, significantly improving more stable ECL signal. Moreover, the Fc-CHO/Phe labeled BSA-AFB1 was used for competitive reaction. Based on the efficient sensing strategy, ECL signal increased accordingly and exhibited linear signal responses with increasing AFB1, which realized a detection limit of 4.56 fg/mL, providing a promising potential on food analysis.

Efficient hydrogen production of phosphonitrilic-bridged metal porphyrin porous covalent organic polymer with a push-pull motif

Rational design of efficient hydrogen evolution reaction (HER) electrocatalysts, constructed with earth-abundant elements, is critical for developing sustainable alternative energy sources. Herein, two phosphonitrilic-bridged metal porphyrin porous covalent organic polymers (COPs) were developed for HER. Compared to CoTPP-PCTCOP, NiTPP-PCTCOP exhibits relative low overpotentials of 140 to reach 10 mA cm−2 for HER in alkaline medium, which is comparable to many previously reported state-of-the-art electrocatalysts. The enhanced HER activity of NiTPP-PCTCOP is associated with its chemical composition and special push-pull structure. Long-term stability analysis of NiTPP-PCTCOP shows that the current density exhibits no obvious deactivation over a long time test. This work demonstrates an effective technique to develop promising HER electrocatalysts, highlighting its advantages by combing phosphonitrilic chloride trimer with metal porphyrins.

Preparation of a Dual-Functionalized Acid-Base Macroporous Polymer via High Internal Phase Emulsion Templating as a Reusable Catalyst for One-Pot Deacetalization-Henry Reaction.

A macroporous dual-functional acid–base covalent organic polymer catalyst poly(St-VBC)-NH2-SO3H was prepared using high internal phase emulsion polymerization using vinylbenzyl chloride (VBC), styrene (St), and divinylbenzene (DVB) as substrates toluene as a porogenic solvent, and subsequent modification with ethylenediamine and 1,3-propane sultone. The role of various amounts of toluene as the porogenic solvent as well as the amount of 1,3-propane sultone (different ratio of acid/base sites) on the structure of the prepared materials have been carefully investigated. The prepared materials were characterized by Fourier transform infrared (FT-IR), CHNS elemental analysis, energy-dispersive X-ray (EDX), elemental mapping, field emission scanning electron microscopy (FE-SEM), and thermalgravimetric analysis (TGA). The catalytic activity of the poly(St-VBC)-NH2-SO3H series with different acid/base densities was assessed for one-pot cascade C–C bond-forming reactions involving deacetylation–Henry reactions. The poly(St-VBC)-NH2-SO3H(20) sample bearing 1.82 mmol/g of N (base site) and 1.16 mmol/g (acid site) showed the best catalytic activity. The catalyst demonstrated superior activity compared to the homogeneous catalysts, poly(St-DVB)-SO3H+EDA, poly(St-VBC)-NH2+chlorosulfonic acid, and poly(St-DVB)-SO3H+poly(St-VBC)-NH2 as the catalyst system. The optimized catalyst showed excellent catalytic performance with 100% substrate conversion and 100% yield of the final product in the one-pot production of β-nitrostyrene from benzaldehyde dimethyl acetal under cascade reactions comprising acid-catalyzed deacetalization and base-catalyzed Henry reactions. It was shown that these catalysts were reusable for up to four consecutive runs with a very slight loss of activity. The excellent performance of the catalyst was attributed to the excellent chemical and physical properties of the developed support since it provides an elegant route for preparing site-isolated acid–base dual heterogenized functional groups and preventing their deactivation via chemical neutralization.

Pyrazine and crown ethers: functional covalent organic polymers for (solar-assisted) high capacity and rate performance lithium-organic battery

Multifunctional two-dimensional (2D) covalent organic polymers (COPs) benefiting from unique features display great potential in lithium-organic batteries yet are rarely reported. In this work, we fabricate a novel conjugated polymer (TQ-COP) functioned with flexible crown ethers and pyrazine redox-active sites, used as an organic rechargeable battery cathode. The Fourier transform infrared spectroscopy (FT-IR) and 13C cross-polarization and magic-angle spinning nuclear magnetic resonance (MAS NMR) verify the chemical identity of redox-active units formed during polymerization. In this structure, pyrazine-redox components exhibit a maximum six-electron transfer per active site, resulting in an initial specific capacity of 162 mA h/g(20 mA/g). Because of macrocyclic cavities and preferential coordination with the alkali metal ions of crown ethers, the rate determining step is changed into a charge transfer process, urging TQ-COP to emerge with a superior rate performance (132 mA h/g at 2 C, 81% vs. 0.1 C). Furthermore, the introduction of crown ethers facilitates photo-excited charge-carriers transfer by narrowing the HOMO-LUMO gap, rendering a photo-assisted lithium-organic battery with significant photovoltage responses and ∼10% improvement of battery round-trip efficiency under illumination, demonstrating its promising capability of solar energy utilization. This work proposes new insights into multifunctional COPs for advanced lithium-organic batteries.

An Initial Covalent Organic Polymer with Closed-F Edges Directly for Proton-Exchange-Membrane Fuel Cells.

Covalent organic polymers (COPs) are a class of rising electrocatalysts for the oxygen reduction reaction (ORR) due to the atomically metrical control of the organic molecular components along with highly architectural robustness and thermodynamic stability even in acid or alkaline media. However, the direct application of pristine COPs as acidic ORR electrocatalysts, especially in device manner, e.g., in proton-exchange-membrane fuel cells (PEMFCs), remains a big challenge. Currently, the decoration toward electronic structures of active sites is considered a vital pathway to enhancing the acidic ORR activity of carbon-based electrocatalysts. Here, an initial F-decorated fully closed π-conjugated quasi-phthalocyanine COP (denoted as COPBTC -F) is reported. The introduction of the closed-F edges stepwise drags more electrons from FeN4 sites in COPBTC -F into the catalyst margin, which weakens the occupied numbers of bonding orbitals between COPBTC -F and OH* intermediates at the rate-determining step, exhibiting over five times intrinsic performance beyond the counterpart without F functionalities (termed as COPBTC ). Significantly, the maximum power density utilizing COPBTC -F as a cathode catalyst in PEMFCs is remarkably increased by an order of magnitude compared with COPBTC , which is a stride forward among catalysts based on a pyrolysis-free conjugated-polymer network in device manner to date.

An AIEgen-based hydrazone-linked covalent organic polymer for solid-state fluorescent materials

The construction of high quantum yield solid-state fluorescent materials is of great importance in preparing organic light-emitting devices. Herein we report an AIEgen-based emissive hydrazone-linked covalent organic polymer (TFBE-TD COP) prepared by a simple solid-state mechanochemical grinding method from 1,1,2,2-tetrakis(4-formyl-(1,1′-biphenyl))ethane (TFBE) and terephthalic tihydrazide (TD) at room temperature. The COP exhibits good emission and very high fluorescence quantum yield (ΦF = 37.7%) in the solid-state because of the synergistic effect of rigid skeleton structure and aggregation induction that restricts the relaxation of tetraphenylethylene (TPE) molecules in the TFBE-TD COP. TFBE-TD COP shows a rapid response and high sensitivity toward trifluoroacetic aid (TFA) gas with significant changes in visual color and luminescence, which could be recovered upon exposure to triethylamine vapor. And the TFBE-TD COP was further coated onto the blue LED to achieve white-light emission. The work provides a general method for preparing AIEgen-based COP and explores its applications in solid-state fluorescent materials for the sensing of toxic gases and the preparation of white LED, offering a new route to the design and application of AIEgen-based COPs.

Lignin-Based Hydrogen-Bonded Covalent Organic Polymers as Functional “Switches” of Modified Atmosphere Packaging Membranes for Preservation of Perishable Foods

Lignin-Based Hydrogen-Bonded Covalent Organic Polymers as Functional “Switches” of Modified Atmosphere Packaging Membranes for Preservation of Perishable Foods

Metal-free oxidative desulfurization with molecular oxygen by using N-enriched porous carbons derived from ionic liquid-loaded covalent-organic polymer

A microporous triazine polymer (MCTP) was prepared and loaded, for the first time, with an N-containing ionic liquid (IL) through a ship-in-a-bottle method. The composite material, IL@MCTP, was pyrolyzed under high temperature to get N-enriched carbonaceous materials. The obtained carbons (denoted ICDCs) were utilized as a metal-free catalyst for the aerobic oxidative desulfurization (ODS) of organic sulfur compounds like dibenzothiophene from a model fuel. The reactivity of ICDCs in ODS was dependent on the nitrogen content and porosity of the carbons. One selected material (ICDC(8)), because of high nitrogen content and adequate porosity, showed a remarkable performance in ODS or removal of dibenzothiophene with a very low activation energy of 23.7 kJ/mol. Radical scavenger experiments and ESR analysis revealed the important role of superoxide anion radicals (•O2−) in oxidation. A plausible reaction mechanism to suggest an important role of nitrogen species in ICDCs to activate O2 (via adsorption on C with a partial positive charge) was proposed. The ODS also can be carried out with air, and the catalyst was reusable for up to the fifth cycle by simple solvent washing. The ICDCs can be a competitive and environment-friendly (metal-free) ODS catalyst, especially using cheap oxidants like air or O2.

A benzimidazole‐linked porphyrin covalent organic polymers as efficient heterogeneous catalyst/photocatalyst

Porphyrins are selected as building units to synthesize porphyrin‐based covalent organic polymers (COPs), which can combine the excellent properties of covalent organic polymers with the fantastic catalytic effect of porphyrin to obtain a heterogeneous catalyst with excellent catalytic activity. In this work, the novel benzimidazole‐linked porphyrin COPs MPp‐BTA (M = 2H, Zn, Co) were synthesized using a new porphyrin with aldehyde group peripherally MPp (M = 2H, Zn, Co) and 1,2,4,5‐tetraminobenzene tetrahydrochloride (BTA) as monomers. The synthesized MPp‐BTA were carefully characterized by FT‐IR, UV–vis, SEM, TEM, TG, and PXRD. As heterogeneous catalyst, MPp‐BTA (M = Zn, Co) shows the high catalytic activity and stability for cycloaddition of CO2 with phenyl glycidyl ether (PGE) under mild conditions (80°C, 0.1 MPa CO2), and the yield of cyclocarbonate can reach 95% and 92% respectively. In addition, the recycling stability of ZnPp‐BTA was investigated, and the yield of cyclocarbonate was still remained at 86% after five cycles. Furthermore, MPp‐BTA (M = 2H, Zn, Co) can be used directly as heterogeneous photocatalysts for selective oxidation of thioanisole to methyl phenyl sulfoxide. To our delight, H2Pp‐BTA shows satisfactory photocatalytic performance, and the yield of methyl phenyl sulfoxide can reach 93% in 4 h.

Solvent-Directed Morphological Transformation in Covalent Organic Polymers

Synthesis of bi-functional covalent organic polymers in two distinctive morphologies has been accomplished by simply switching the solvent from DMF to DMSO when 1,3,5-tribenzenecarboxyldehyde and 2,5-diaminobenzene sulfonic acid were reacted via Schiff base condensation reaction to afford covalent organic polymers (COPs) encompassing flower (F-COPDMF)- and circular (C-COPDMSO)-type morphologies. Chemical and morphological natures of the synthesized COPs were compared by characterization using TEM, SEM, XRD, FT-IR, and XPS analysis techniques. Besides diverse morphology, both the polymeric materials were found to comprise similar chemical natures bearing protonic acid–SO3H and Lewis base–C=N functionalities. Subsequently, both the COPs were evaluated for the synthesis of hydroxymethylfurfural (HMF) by the dehydration of fructose to investigate their morphology-dependent catalytic activity.

Covalent organic polymers for aqueous and organic solvent nanofiltration

Here we present the preparation of a novel positively charged covalent organic polymer (COP) based nanofiltration membrane. The porous COP selective layer grows on top of a polybenzimidazole (PBI) support from coupling reaction of 1,3,5-tris(bromomethyl)benzene and 4,4′−dipyridyl in alkaline conditions. Chemical and morphological analyses confirm the formation of a thin layer of COP (less than 50 nm), which is also evidenced by its high water permeance and salt retentions. Moreover, it is shown that COP membranes can form hydrogen bonds with HNO3, leading to a tighter membrane pore size that increases the NaCl retention from 46% to 75% without significantly losing its permeance. Further, the composite membranes demonstrated exceptional solvent and pH stabilities. The COP membranes showed a molecular weight cut off between 400 and 1000 g mol−1 together with pure solvent permeances of 0.91, 2.4, 3.3, 7.1 and 9.5 Lm−2h−1bar−1 toward dimethylformamide (DMF), ethanol, acetone, methanol an acetonitrile, respectively. The remarkable performance together with the stability in harsh environments make the newly developed COP membranes an attractive candidate for extreme nanofiltration.

Construction of an ultra-small hydrazone-linked covalent organic polymer for selective fluorescent detection of ferric ion in aqueous solution

A novel ultra-small hydrazone-linked covalent organic polymer (UHCOP) was synthesized based on the Schiff-base reaction between 2,4,6-trihydroxy-1,3,5-benzenetricarbaldehyde and 1,4-benzenedicarbohydrazide at room temperature and utilized as a sensitive fluorescent sensor for rapid (<2 min) and selective detection of Fe3+ in aqueous solution. The prepared UHCOP displayed ultra-small size with the diameter of 7.98 ± 0.97 nm and gave a stable fluorescent emission at 510 nm. UHCOP exhibited good sensitivity and highly selectivity towards Fe3+. The coordination interaction between UHCOP and Fe3+ resulted in the obviously aggregation-caused quenching response of UHCOP. The linear range was from 5.0 μM to 1.4 mM (R2 = 0.999) with the detection limit of 2.5 μM. Finally, UHCOP has been successfully applied in the detection of Fe3+ in real water samples, proving the fabricated UHCOP is promising as a sensitive fluorescent sensor for selective detection of Fe3+ in aqueous solution.

Covalent organic framework with active C=O/C=N groups for high performance cathode material for lithium‐ion batteries

The large-scale applications of energy storage system via lithium-ion batteries (LIBs) put forward demands for high capacity, high safety, and low cost of materials. Covalent organic polymers have attracted extensive attention because of their high capacity, flexible structural design, high safety, abundance, and low cost. Here, 2,3,5,6-tetraamino-p-benzoquinone and hexaketocyclohexane octahydrate were chosen as monomers to construct the covalent organic framework (TH-COF) cathode materials with active C=O and C=N groups. The TH-COF was further composed with reduced graphene oxide (rGO) and the prepared TH-COF/rGO cathode provided a capacity of 135 mAh g−1 after 600 cycles at 1 C current density. In addition, after 100 cycles, the cathode delivered capacities of 118 and 73 mAh g−1 at the high current densities of 5 C and 20 C, respectively, displaying superior rate performances. The TH-COF/rGO electrode exhibited high capacity and stability, making it a promising cathode material for the next generation LIBs.

Rational Construction of Yolk-Shell Bimetal-Modified Quinonyl-Rich Covalent Organic Polymers with Ultralong Lithium-Storage Mechanism.

Covalent organic polymers are attracting more and more attention for energy storage devices due to their lightweight, molecular viable design, stable structure, and environmental benignity. However, low charge-carrier mobility of pristine covalent organic materials is the main drawback for their application in lithium-ion batteries. Herein, a yolk-shell bimetal-modified quinonyl-rich covalent organic material, Co@2AQ-MnO2, has been designed and synthesized by in situ loading of petal-like nanosized MnO2 and coordinating with Co centers, with the aim to improve the charge conductivity of the covalent organic polymer and activate its Li-storage sites. As investigated by in situ FT-IR, ex situ XPS, and electrochemical probing, the quinonyl-rich structure provides abundant redox sites (carbonyl groups and π electrons from the benzene ring) for lithium reaction, and the introduction of two types of metallic species promotes the charge transfer and facilitates more efficient usage of active energy-storage sites in Co@2AQ-MnO2. Thus, the Co@2AQ-MnO2 electrode exhibits good cycling performance with large reversible capacity and excellent rate performance (1534.4 mA h g-1 after 200 cycles at 100 mA g-1 and 596.0 mA h g-1 after 1000 cycles at 1000 mA g-1).

The aminated covalent organic polymers for reversible removal of concurrent perfluorooctane sulfonate and dichromate

The reversible removal of concurrent perfluorinated compounds and heavy metal ions is highly desirable but challenge in water remediation. Herein, we present a tetraethylenepentamine-modified covalent organic polymer (COP-NH2) containing flexible multi-amines and hydrophobic triptycene through post-synthetic amidation reaction of carboxyl-containing covalent organic polymer. The sorption behaviors of COP-NH2 toward perfluorooctane sulfonate (PFOS) and dichromate were investigated in terms of the adsorption kinetics, isotherms, simultaneous removal capability and reusability. The maximum uptake capacities of PFOS and dichromate on COP-NH2 are 1.40 mmol g−1 and 304.9 mg g−1, respectively, while their initial adsorption rates are as high as 6.45 mmol g-1h−1 and 164.2 mg g−1 min−1, respectively. Both of them surpass majority of the sorbents of the environmental contaminants. Importantly, PFOS and dichromate in the stimulated electroplating wastewater could be simultaneously and reversibly removed in high uptake efficiency over 99%. The promising performance is mainly attributed to protonation of the amines in COP-NH2, the resultant electrostatic interactions have been confirmed to play dominant roles in both PFOS and dichromate adsorption. This work provides multifunctional sorbents for reversible removal of concurrent contaminants from wastewater.

Facile synthesis and evaluation of three magnetic 1,3,5-triformylphloroglucinol based covalent organic polymers as adsorbents for high efficient extraction of phthalate esters from plastic packaged foods.

Three covalent organic polymers (COPs) were successfully fabricated by room-temperature solvent-free mechanochemical grinding method between 1,3,5-triformylphloroglucinol (TP) and p-phenyl enediamine (COP1), benzidine (COP2), 4, 4″-diamino-p-terphenyl (COP3), and followed by coprecipitation on the surface of Fe3O4 nanoparticles to form three corresponding magnetic Tp-series COPs. The fabricated magnetic COPs were evaluated and then applied for the extraction of phthalate esters from food samples before gas chromatography-tandem spectrometry analysis. Magnetic COP2 exhibited the highest extraction efficiency, which can be attributed to its larger pore size, and its strong hydrophobic and π-π interactions with phthalate esters. The method possessed good linearity (10-1000μg·kg-1), high sensitivity (0.29-2.59µg·kg-1 for LODs and 0.97-8.63µg·kg-1 for LOQs), and satisfactory recoveries (70.2-108.1%) with relative standard deviations lower than 5.2%. This method has potentials for high efficient separation/preconcentration of hydrophobic phthalate esters from foods.

Nitrogen-rich two-dimensional π-conjugated porous covalent quinazoline polymer for lithium storage

The feasibility of assorted characteristics of fast charge-transport, abundance active sites, and controlled molecular designing of the π-conjugated porous two-dimensional covalent organic polymer offers exclusive alternative electrode materials for lithium storage. However, the functioning of an organic polymer electrode in terms of specific capacity, cycle life, and rate performance is still lacking. In this work, we report the theoretical design and corresponding practical development of a nitrogen-rich two-dimensional π-conjugated porous covalent quinazoline polymer (HAT-CQP). The results show that HAT-CQP as anode for lithium-ion batteries can produce an excellent electrochemical performance.The discharge-specific capacity reaches 478 mAh g−1 even after 510 cycles, and a 82.3% of capacity retention rate is acquired at 800 mAg−1. The X-ray photoelectron spectroscopy results along with theoretical calculations reveal that the designed structure of HAT-CQP can store 7 Li+ located on a pyrazine-like C=N and conjugated heterocycles.

Novel triazine-based cationic covalent organic polymers for highly efficient and selective removal of selenate from contaminated water

Selenium (Se) removal from contaminated water has become a major environmental problem in recent years. Designing efficient and selective materials for selenium adsorption is urgent and still represents a great challenge. Herein, two novel cationic covalent triazine frameworks (CTFS-Cl and CTFL-Cl) are developed for the first time and employed as a new class of Se adsorbents. The results from systematic adsorption experiments indicate that these materials can adsorb SeO42- in a wide range of pH values (2−11) with fast kinetics (5 min), outstanding adsorption capacity, and excellent selectivity over other competing anions. The maximum adsorption capacity achieved (149.3 mg/g by CTFS-Cl) constitutes one of the highest values among the organic polymeric materials. More importantly, after a single step adsorption, these materials can reduce the Se concentrations to lower than 10 μg/L, the lowest drinking water standard in the world. The adsorption mechanism was probed by XPS technique, EDS analysis, adsorption experiments, and DFT calculations, which reveals that anion exchange between Cl- and SeO42- is the main driving force for Se adsorption. Additionally, CTFS-Cl and CTFL-Cl perform well toward real contaminated river water sample with the residual Se being less than 8.49 μg/L. This work demonstrates the excellent performance of CTFs-based materials with great application prospect for Se removal in contaminated water treatment.

Large‐Area Covalent Organic Polymers Membrane via Sol–Gel Approach for Harvesting the Salinity Gradient Energy (Small 20/2022)

Energy Harvesting There are salinity gradients at the confluence of the river and sea, which contain tremendous amounts of energy. In article number 2107600, Jin Zhai and co-workers fabricate a covalent organic polymers membrane for harvesting the salinity gradient energy. The membrane has better properties and can be prepared in large areas, which is expected to be applied in the future to real-world situations.