Porous Covalent Organic Polymers Research Articles

Designing an electrochemical aptasensor based on a microstructure porous-covalent organic polymer for the determination of 2,4,6-trinitrotoluen in water and soil samples

A selective electrochemical aptasensor assessment based on a microstructure porous-covalent organic polymer (MP-COP) was introduced and applied for 2,4,6-Trinitrotoluen (TNT) sensing. The synthesis of MP-COP involves the formation of an amide bond by coupling carboxylic acids and amine groups using trimesic acid. The synthesized MP-COP was used to modify the glassy carbon electrode (GCE) due to its ability to enhance electrochemical activity. The GCE is modified with the MP-COP and aptamer to create a sensing substrate, with the goal of improving the aptasensor’s electrochemical performance for TNT detection. Electrochemical impedance spectroscopy, differential pulse voltammetry, and cyclic voltammetry were applied for the evaluation of the introduced aptasensor in [Fe(CN)6]3−/4− probe. Moreover, it was delineated using fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller. The suggested aptasensor for TNT has a limit of detection of 0.0003 pM and the linear range from 0.001 to 100 pM. The usability of the proposed aptasensor for TNT measurement in actual samples was examined with the recovery range from 98.30 to 102.40 %. It seems that the proposed strategy can be expanded to design of electrochemical aptasensors.

Electrochemical sensing of Pb2+, Cu2+, and Hg2+ by an aminoclay-based porous covalent organic polymer/ multi-walled carbon nanotubes modified glassy carbon electrode

We present a novel electrochemical sensor for the simultaneous detection of Lead (Pb2+), Copper (Cu2+), and Mercury (Hg2+) ions in seafood samples using differential pulse anodic stripping voltammetry (DPASV) technique. The sensor incorporates an aminoclay-based porous covalent organic polymer (AC-PCOP) derived from the polymerization of aminoclay and 1,3,5-benzenetricarboxylic acid (trimesic acid). To enhance conductivity, the AC-PCOP is combined with multi-walled carbon nanotubes (MWCNTs) and utilized for modifying the surface of the glassy carbon electrode (GCE). The AC-PCOP was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, and infrared spectroscopy (IR). These analyses confirmed the presence of a hierarchical architecture in the AC-PCOP, which exhibited a spherical shape. The proposed modifier facilitates the deposition-stripping process and electron diffusion between electrolyte and heavy metal ions. Optimized conditions yielded limit of detections (LODs) of 0.0006, 0.0016, and 0.0003 nM, with linear ranges from 0.002 to 1000 nM, 0.005 to 1000 nM, and 0.001 to 1000 nM for Pb2+, Cu2+, and Hg2+, respectively. The sensor successfully measured these ions in seafood samples. Control experiments and validation were performed using cold vapor atomic absorption spectrometry (CVAAS) to determine the ions in the chosen food samples.

Novel Porous Organic Polymer Catalyst with Phosphate and Sulfonic Acid Sites for Facile Esterification of Levulinic Acid.

Biomass-derived value-added materials such as levulinic acid (LA) are favorable natural resources for producing ester-based biolubricants owing to their biodegradability, nontoxicity, and excellent metal-adhering properties. However, highly active catalysts must be developed to carry out efficient esterification of LA with aliphatic alcohols, especially long-chain aliphatic alcohols. In this study, we developed a novel porous covalent organic polymer catalyst (BPOP-SO3H) with dual acid sites, phosphate and sulfonic acid sites, for the esterification of LA. The prepared BPOP-SO3H catalyst was verified using various surface analysis techniques. BPOP-SO3H exhibited 98% LA conversion with n-butanol and 99% selectivity for butyl levulinate ester within 30 min, which is superior to that of most reported catalysts. BPOP-SO3H also showed high LA conversion and ester selectivity when other aliphatic alcohols were used. Moreover, BPOP-SO3H showed good recyclability for five consecutive cycles. We believe that incorporating a high density of acid sites into a porous polymer with a large surface area and hierarchical pores is a promising approach for developing heterogeneous acid catalysts for the production of alkyl levulinate esters from LA.

Novel phosphite-based porous organic polymers for efficient removal of sulfur-containing antibiotics from water

Water contamination by pharmaceutical and personal care products (PPCPs), particularly sulfur- containing PPCPs such as sulfamethoxazole (SMX), is a major environmental concern. In this study, phosphite-based porous covalent organic polymers (PCOP-I and PCOP-II) with numerous aromatic and acidic phosphite sites, large surface areas (∼1263 m2/g) and hierarchical pore structures are successfully synthesized. Compared with previously reported benchmark adsorbents, PCOPs exhibited among the largest SMX adsorption capacities (∼296.6 mg g−1) and superior SMX adsorption kinetics (10 min). The superior SMX adsorption performance of PCOPs can be explained by the π–π interactions and hydrogen bonding within hierarchical pore structures with large surface areas. The SMX adsorptive capacities of PCOPs were not greatly influenced by the presence of possible competing metal ions in water, which were retained after cyclic adsorption and regeneration. These results indicate that incorporating numerous aromatic and acidic phosphite sites into COPs with hierarchical pores and large surface areas can be used to develop adsorbents that can efficiently remove sulfur-containing PPCPs from water.

CTAB assisted evaporation-induced self-assembly to construct imidazolium-based hierarchical porous covalent organic polymers for ReO4-/TcO4- removal

Evaporation-induced self-assembly method (EISA) was a facile and reliable method to synthesize porous materials. Herein, we report a kind of hierarchical porous ionic liquid covalent organic polymers (HPnDNH2) under cetyltrimethylammonium bromide (CTAB) assisted by EISA for ReO4-/TcO4- removal. Unlike covalent organic frameworks (COFs), which usually needed to be prepared in a closed environment or with a long reaction time, HPnDNH2 in this study was prepared within 1 h in an open environment. It was worth noting that CTAB not only served as a soft template for forming pore, but also induced ordered structure, which was verified by SEM, TEM, and Gas sorption. Benefit from its hierarchical pore structure, HPnDNH2 exhibited higher adsorption capacity (690.0 mg g−1 for HP1DNH2 and 808.7 mg g−1 for HP1.5DNH2) and faster kinetics for ReO4-/TcO4- than 1DNH2 (without employing CTAB). Additionally, the material used to remove TcO4- from alkaline nuclear waste was seldom reported, because combining features of alkali resistance and high uptake selectivity was not easy to achieve. In this study, in the case of HP1DNH2, it displayed outstanding adsorption efficiency toward aqueous ReO4-/TcO4- in 1 mol L−1 NaOH solution (92%) and simulated Savannah River Site High-level waste (SRS HLW) melter recycle stream (98%), which could be a potentially excellent nuclear waste adsorbing material.

An Imine-Based Porous 3D Covalent Organic Polymer as a New Sorbent for the Solid-Phase Extraction of Amphenicols from Water Sample.

In this paper, an imine-based porous 3D covalent organic polymer (COP) was synthesized via solvothermal condensation. The structure of the 3D COP was fully characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and powder X-ray diffractometry, thermogravimetric analysis, and Brunauer-Emmer-Teller (BET) nitrogen adsorption. This porous 3D COP was used as a new sorbent for the solid-phase extraction (SPE) of amphenicol drugs, including chloramphenicol (CAP), thiamphenicol (TAP), and florfenicol (FF) in aqueous solution. Factors were investigated for their effects on the SPE efficiency, including the types and volume of eluent, washing speed, pH, and salinity of water. Under the optimized conditions, this method gave a wide linear range (0.1-200 ng/mL) with a high correlation coefficient value (R2 > 0.99), low limits of detection (LODs, 0.01-0.03 ng/mL), and low limits of quantification (LOQs, 0.04-0.10 ng/mL). The recoveries ranged from 83.98% to 110.7% with RSDs ≤ 7.02%. The good enrichment performance for this porous 3D COP might contribute to the hydrophobic and π-π interactions, the size-matching effect, hydrogen bonding, and the good chemical stability of 3D COP. This 3D COP-SPE method provides a promising approach to selectively extract trace amounts of CAP, TAP, and FF in environmental water samples in ng quantities.

A novel metal-free porous covalent organic polymer for efficient room-temperature photocatalytic CO2 reduction via dry-reforming of methane

At room temperature, the conversion of greenhouse gases into valuable chemicals using metal-free catalysts for dry reforming of methane (DRM) is quite promising and challenging. Herein, we developed a novel covalent organic porous polymer (TPE-COP) with rapid charge separation of the electron–hole pairs for DRM driven by visible light at room temperature, which can efficiently generate syngas (CO and H2). Both electron donor (tris(4-aminophenyl)amine, TAPA) and acceptor (4,4′,4″,4‴-((1 E,1′E,1″E, 1‴E)-(ethene-1,1,2,2-tetrayltetrakis (benzene-4,1-diyl))tetrakis (ethene-2,1-diyl))tetrakis (1-(4-formylbenzyl)quinolin-1-ium), TPE-CHO) were existed in TPE-COP, in which the push–pull effect between them promoted the separation of photogenerated electron–hole, thus greatly improving the photocatalytic activity. Density functional theory (DFT) simulation results show that TPE-COP can form charge-separating species under light irradiation, leading to electrons accumulation in TPE-CHO unit and holes in TAPA, and thus efficiently initiating DRM. After 20 h illumination, the photocatalytic results show that the yields reach 1123.6 and 30.8 μmol g−1 for CO and H2, respectively, which are significantly higher than those of TPE-CHO small molecules. This excellent result is mainly due to the increase of specific surface area, the enhancement of light absorption capacity, and the improvement of photoelectron-generating efficiency after the formation of COP. Overall, this work contributes to understanding the advantages of COP materials for photocatalysis and fundamentally pushes metal-free catalysts into the door of DRM field.

Porous Covalent Organic Polymer Coordinated Single Co Site Nanofibers for Efficient Oxygen-Reduction Cathodes in Polymer Electrolyte Fuel Cells.

Nitrogen-coordinated single-cobalt-atom electrocatalysts, particularly ones derived from high-temperature pyrolysis of cobalt-based zeolitic imidazolate frameworks (ZIFs), have emerged as a new frontier in the design of oxygen reduction cathodes in polymer electrolyte fuel cells (PEFCs) due to their enhanced durability and smaller Fenton effects related to the degradation of membranes and ionomers compared with emphasized iron-based electrocatalysts. However, pyrolysis techniques lead to obscure active-site configurations, undesirably defined porosity and morphology, and fewer exposed active sites. Herein, a highly stable cross-linked nanofiber electrode is directly prepared by electrospinning using a liquid processability cobalt-based covalent organic polymer (Co-COP) obtained via pyrolysis-free strategy. The resultant fibers can be facilely organized into a free-standing large-area film with a uniform hierarchical porous texture and a full dispersion of atomic Co active sites on the catalyst surface. Focused ion beam-field emission scanning electron microscopy and computational fluid dynamics experiments confirm that the relative diffusion coefficient is enhanced by 3.5 times, which can provide an efficient route both for reactants to enter the active sites, and drain away the produced water efficiently. Resultingly, the peak power density of the integrated Co-COP nanofiber electrode is remarkably enhanced by 1.72 times along with significantly higher durability compared with conventional spraying methods. Notably, this nanofabrication technique also maintains excellent scalability and uniformity.

Systematic Modulation of Thiol Functionalities in Inexpensive Porous Polymers for Effective Mercury Removal.

Through accumulation, mercury contamination in aquatic systems still poses serious health risks despite the strict regulations on drinking water and industrial discharge. One effective strategy against this is adsorptive removal, in which a suitably functionalized porous material is added to water treatment protocols. Thiol (SH) group-grafted structures perform commendably; however, insufficient attention is paid to the cost, scalability, and reusability or how the arrangement of sulfur atoms could affect the HgII binding strength. We used an inexpensive and scalable porous covalent organic polymer (COP-130) to systematically introduce thiol functional groups with precise chain lengths and sulfur content. Thiol-functionalized COP-130 demonstrates enhanced wettability and excellent HgII uptake of up to 936 mg g-1 , with fast kinetics and exceptionally high selectivity. These Hg adsorbents are easily regenerated with HCl and can be used at least six times without loss of capacity even after treatment with strong acid, a rare performance in the domain of Hg-removal research.

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.

Covalent Organic Polymer Nanoparticle-Supported Monolithic Foams for Separation of Nitrotoluene Isomers

The combination of micron-scale macropores with meso-/micropores into three-dimensional (3D) macroscopic architectures could give increasing attention to both fast diffusion and mass transfer and exposure of the intrinsic micropores, thereby improving the performance and realizing the real-world applicability of nanoscale functionalized materials. In this report, the emulsion-droplet-templated method was used for the preparation of a hierarchically porous macroscopic covalent organic polymer (COP) monolithic foam, showing compressibility, high mass transfer, and excellent chromatographic separation capacity. The as-synthesized COP nanoparticles with the size of about 40 nm possessed good crystallization and high chemical and thermal stability. More importantly, the resulting COP nanoparticles showed interfacial activity, absorbing and accumulating the water/mesitylene interface, thus producing the COP nanoparticle film. As a result, a series of Pickering emulsions stabilized by COP nanoparticles were formed. Emulsion droplets of approximately 4.90 μm could serve as templates, producing hierarchically porous COP monolithic foams via freeze-drying of the starting Pickering emulsions. In view of the effective merging of macropores with meso-/micropores, the very thin disklike COP monolith (1 mm height × 10 mm i.d.) can serve as a separation column, which is highly efficient in differentiating the isomers of p- < o- < m-nitrotoluenes and chloronitrobenzenes. Clearly, the macropores guarantee high mass transfer, while the micropores provide many active sites. Therefore, the resulting COP foam shows excellent chromatographic separation capacity. Finally, the as-prepared COP monolithic foam has great potential as a prospective chromatographic column for highly efficient separation of isomers.

Triazine-based N-rich porous covalent organic polymer for the effective detection and removal of Hg (II) from an aqueous solution

Triazine-based N-rich covalent organic polymer (TBN-1) was prepared for effective removal and selective detection of Hg2+ from model solutions. The π-π conjugated structure formed by alternating electron-deficient triazine group and electron-rich benzene group promotes the electron transfer and strong fluorescence. The ultra-high specific surface area and abundant metal complex groups provide excellent adsorption sites for heavy metals. The TBN-1 suspension has obvious fluorescence quenching effect when encountering Hg2+ even when the solutions are treated with co-ions and humic acid. The merits of TBN-1 are unreservedly manifested when further testing the adsorption kinetics of TBN-1 for Hg2+ removal. With the maximum adsorption capacity of 1630 mg g−1, 99.99% of Hg2+ can be removed within 20 min from a 10 ppm solution using TBN-1. The covalent organic polymer (COP) also exhibits a high stability in a wide range of pH and a significant selectivity for Hg2+. About 99.9% Hg2+ can be adsorbed in acidic, co-ions competitive and humic acid contaminated solutions. The TBN-1 can be also reused for at least 5 cycles with acceptable Hg2+ adsorption capacity retention. The mechanism for the excellent Hg2+ adsorption performance of TBN-1 is revealed by coupling physico-chemical model fitting, chemical computation, and experimental characterization, which indicates the coordination and cation-π effects and high electron density of the material to facilitate its complexation with Hg2+. This work offers new prospects for the application of triazine-based COPs for environmental remediation.

Porous Covalent Organic Polymers for Efficient Fluorocarbon‐Based Adsorption Cooling

AbstractAdsorption‐based cooling is an energy‐efficient renewable‐energy technology that can be driven using low‐grade industrial waste heat and/or solar heat. Here, we report the first exploration of fluorocarbon adsorption using porous covalent organic polymers (COPs) for this cooling application. High fluorocarbon R134a equilibrium capacities and unique overall linear‐shaped isotherms are revealed for the materials, namely COP‐2 and COP‐3. The key role of mesoporous defects on this unusual adsorption behavior was demonstrated by molecular simulations based on atomistic defect‐containing models built for both porous COPs. Analysis of simulated R134a adsorption isotherms for various defect‐containing atomistic models of the COPs shows a direct correlation between higher fluorocarbon adsorption capacities and increasing pore volumes induced by defects. Combined with their high porosities, excellent reversibility, fast kinetics, and large operating window, these defect‐containing porous COPs are promising for adsorption‐based cooling applications.

Porous Covalent Organic Polymers for Efficient Fluorocarbon-Based Adsorption Cooling.

Adsorption-based cooling is an energy-efficient renewable-energy technology that can be driven using low-grade industrial waste heat and/or solar heat. Here, we report the first exploration of fluorocarbon adsorption using porous covalent organic polymers (COPs) for this cooling application. High fluorocarbon R134a equilibrium capacities and unique overall linear-shaped isotherms are revealed for the materials, namely COP-2 and COP-3. The key role of mesoporous defects on this unusual adsorption behavior was demonstrated by molecular simulations based on atomistic defect-containing models built for both porous COPs. Analysis of simulated R134a adsorption isotherms for various defect-containing atomistic models of the COPs shows a direct correlation between higher fluorocarbon adsorption capacities and increasing pore volumes induced by defects. Combined with their high porosities, excellent reversibility, fast kinetics, and large operating window, these defect-containing porous COPs are promising for adsorption-based cooling applications.

Extensive Screening of Solvent‐Linked Porous Polymers through Friedel–Crafts Reaction for Gas Adsorption

Scalability, cost, and feasibility of porous structures in gas capture are prerequisites for emerging materials to be promising in the industry. Herein, a simpler variant of Friedel−Crafts’ synthesis of highly porous covalent organic polymers (COPs) based on an unprecedented solvent‐mediated crosslinking is presented. Alkyl chlorides behave as both solvents and linkers in the presence of AlCl3. Studies on three classes of 18 different monomers using dichloromethane, chloroform, and 1,2‐dichloroethane lead to producing 29 new COPs (124−152). Polymers are characterized by Fourier‐transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR) spectroscopy, elemental composition analysis, scanning electron microscope (SEM), thermogravimetric analysis (TGA), and porosity analyzer. The synthesized COPs exhibit structures from nonporous to highly porous morphologies with Brunauer–Emmett–Teller (BET) surface areas as high as 1685 m2 g−1. These COPs show high gas uptake toward CO2 (up to 4.71 mmol g−1 at 273 K, 1.1 bar), CH4 (up to 1.31 mmol g−1 at 273 K, 1.1 bar), and H2 (up to 2.02 wt% at 77 K, 1.1 bar). The findings point to significant potential in producing sustainable porous materials through simple and scalable methodology developed here.

Alkyl‐Linked Porphyrin Porous Polymers for Gas Capture and Precious Metal Adsorption

In gas adsorption and metal recovery, inexpensive and covalently bonded porous polymers offer industrial feasibility, despite the challenge of having reactive functionalities while maintaining porosity. Herein, three highly porous covalent organic polymers (COPs), COP‐210, COP‐211, and COP‐212, with porphyrin functionalities that are readily synthesized by a Friedel–Crafts reaction using chlorinated solvents as linkers are reported. The polymers exhibit competitive adsorption capacities for CO2, H2, and CH4. Their porphyrin sites proved particularly effective in precious metal recovery, where COPs exhibit high selectivity toward gold, platinum, palladium, and silver. Analysis reveals that reductive metal capture is prevalent for gold and silver. Platinum is also captured through a combination of reduction and chelation. The gold adsorption capacities are 0.901–1.250 g g−1 with fast adsorption kinetics at low pH. COP‐212 selectively recovers 95.6% of gold from actual electronic waste (e‐waste) collected from junkyards. The results show that the inexpensive and scalable porous porphyrin polymers offer great potential in gas capture, separation, and precious metal recovery.

Sulfur-modified porous covalent organic polymers as bifunctional materials for efficient fluorescence detection and fast removal of heavy metal ions

A sulfur-modified covalent organic polymer is synthesized, and it can achieve bifunctional application for Hg2+ fluorescence detection and removal from wastewater.

Covalent Amine Tethering on Ketone Modified Porous Organic Polymers for Enhanced CO2 Capture.

Effective removal of excess greenhouse gas CO2 necessitates new adsorbents that can overcome the shortcomings of the current capture methods. To achieve that, porous materials are often modified post-synthetically with reactive amine functionalities but suffer from significant surface area losses. Herein, we report a successful amine post-functionalization of a highly porous covalent organic polymer, COP-130, without losing much porosity. By varying the amine substituents, we recorded a remarkable increase in CO2 uptake and selectivity. Ketone functionality, a rarely accessible functional group for porous polymers, was inserted prior to amination and led to covalent tethering of amines. Interestingly, aminated polymers demonstrated relatively low heats of adsorption, which is useful for the rapid recyclability of materials, due to the formation of suspected intramolecular hydrogen bonding.

Phosphonic acid loaded covalent imine networks for proton-conducting membranes

Triazine-based covalent organic polymers (COPs) have substantially concerned as a hopeful proton-conducting medium. Generally, encapsulating protonphore molecules into porous COPs is a potential tactics to improve the proton conductivity (PC). Herein, the COP-based proton conductor is fabricated by immobilizing nitrilotrimethylphosphonic acid (NTP) molecules into the pores of nitrogen-rich covalent imine network (CIN) to give NTP/CIN, further followed by blending NTP/CIN as filler into chitosan (CS, a deacetylated form of chitin) to form hybrid membranes (NTP/CIN@CS). NTP/CIN@CS possesses relatively higher PC of 7.8 × 10−3 S cm−1 under ~98% RH at 328 K, ranging in the most conductive COF-based hybrids, which is 71- and 17-folds than those of pristine CS and CIN@CS. The basic functional units contained from CIN backbone, phosphate groups derived from NTP and amino and hydroxyl groups at CS matrix, along with water, conduct the transfer of proton in the hybrid membrane. The relatively high water uptake (W.U.) and ion exchange capacity (IEC) of NTP/CIN@CS also contribute to form continuous and steady H-transport channel, and thus greatly enhance PC. The inspiration that nitrogen-rich COF framework federated with proton carrier tenders a new path to discern solid-state electrolyte.

HiGee Strategy toward Rapid Mass Production of Porous Covalent Organic Polymers with Superior Methane Deliverable Capacity

AbstractHigh porosity with well‐defined molecular reticulation along with strong stability is desired for natural gas delivery. The catalyzed Yamamoto‐type Ullmann cross‐coupling route with efficient terminal halogen removal capability is currently used to prepare porous organic materials with high specific surface area as well as ultrahigh hydrothermal stability. As a typical fast coupling reaction, the traditional stirred solvothermal approach shows the limitation of macroscopic reaction kinetics due to the increasing viscosity of the reaction mixture with the molecular network growth until it turns to a jelly‐like consistency. Herein, a high‐gravity chemical synthetic strategy to achieve rapid and economical preparation of a class of, but not limited to, covalent organic polymers (COPs) with high hydrothermal stability using the Ullman cross‐coupling route is described. The viscous fluid is vigorously split into homogeneous microdroplets through the rotating packed bed (RPB) under the HiGee environment. The HiGee approach shortens the traditional reaction time from 600 to 15 min as well as reduces the usage of high‐cost nickel (0) catalyst by 40 wt%. Specially, the COP‐10 obtained with the HiGee approach displays an excellent deliverable methane capacity of 415 cm3 STP g−1 at 298 K with working pressures 5–65 bar, which is higher than that of most reported porous organic materials.