Porphyrin-based Covalent Organic Frameworks Research Articles

Protonated Z-scheme CdS-covalent organic framework heterojunction with highly efficient photocatalytic hydrogen evolution

The low efficiency of photocatalytic hydrogen production from water is mainly suffer from limited light absorption, charge separation and water delivery to the active centers. Herein, an inorganic–organic Z-scheme heterojunction (CdS-COF-Ni) is constructed by in-situ growth of CdS nanosheets on the porphyrin-based covalent organic framework with nickel ions (COF-Ni) in the porphyrin centers. A built-in electric field is formed at the interface, which accelerates the separation and transfer of photogenerated charges. Moreover, through the surface protonation treatment in ascorbic acid (AC) solution, the hydrophilicity of the obtained composite is obviously increased and facilitates the transport of water molecules to the photocatalytic centers. Under the synergistic effect of the interfacial interaction and surface protonation treatment, the photocatalytic hydrogen production rate is optimized to be 18.23 mmol h−1 g−1 without adding any cocatalysts, which is 21 times that of CdS. After a series of photoelectrochemical measurements, in situ X-ray photoelectron spectroscopy (XPS) analysis, and density functional theory (DFT) calculations, it is found that the photocatalytic charge transfer pathway conforms to the Z-scheme mechanism, which not only greatly accelerates the separation and transfer of photogenerated charges, but also retains a high reduction capacity for water splitting. This work offers a good strategy for constructing highly efficient organic–inorganic heterojunctions for water splitting.

2D Porphyrin-Based Covalent Organic Framework/PEG Composites: A Rational Strategy for Photocatalytic Hydrogen Evolution.

Two-dimensional porphyrin-based covalent organic frameworks (2D-por-COFs) have gained significant attention as attractive platforms for efficient solar light conversion into hydrogen production. Herein, we found that introducing transition metal zinc and polyethylene glycol (PEG) into 2D-por-COFs can effectively improve the photocatalytic hydrogen evolution performance. The photocatalytic hydrogen evolution rate of ZnPor-COF is 2.82 times higher than that of H2Por-COF. Moreover, ZnPor-COF@PEG has the highest photocatalytic hydrogen evolution efficiency, which is 1.31 times and 3.7 times that of pristine ZnPor-COF and H2Por-COF, respectively. The filling of PEG makes the layered structure of COFs more stable. PEG reduced the distortion and deformation of the carbon skeleton after the experiment of photocatalytic hydrogen evolution. The layered stacking and crystallization of 2D-por-COFs are also enhanced. Meanwhile, the presence of PEG also accelerates the transfer of excited electrons and enhances the photocatalytic hydrogen evolution activity. This strategy would provide valuable insights into the design of 2D-por-COFs as efficient solid photocatalysts for solar-driven hydrogen production. This article is protected by copyright. All rights reserved.

Facile synthesis of novel porphyrin-based covalent organic frameworks integrated with Au nanoparticles for highly sensitive detection of organophosphorus pesticide residues

Organophosphorus pesticides (OPs) residues in agricultural products such as vegetables, fruits, and grains pose a threat to food safety and human health. In this work, a novel and highly sensitive electrochemical biosensor was developed for OPs residues detection in real sample, based on the immobilization of acetylcholinesterase (AChE) by electrostatic adsorption on a glassy carbon electrode (GCE) modified with composite nanomaterials of porphyrin-based covalent organic frameworks (p-COFs) loaded by gold nanoparticles (AuNPs) and poly (diallyldimethylammonium chloride) (PDDA). Due to the synergistic effect of p-COFs, AuNPs and PDDA, the fabricated biosensor displayed the remarkable properties with the high electrocataytic activity, and excellent biocompatibility, resulting in a significant signal amplification of as-prepared biosensor. Under optimized conditions, the biosensor showed excellent sensing performances for the detection of methyl parathion (MP), with wide linear ranges from 1.9 × 10−9–3.8 × 10−5 M and a low detection limit as low as 2.3 × 10−10 M, as well as the satisfactory selectivity, excellent reproducibility, anti-interference properties and good stability. It was also successfully applied to the monitoring of MP content in vegetables and fruits, which may be explore a new opportunity for the potential utilization in analysis field.

Anchoring of silver nanoparticles by a zinc-porphyrin covalent organic framework for synergistic photodynamic sterilization

Porphyrin-based covalent organic frameworks (Por-COFs) show great promise in photodynamic sterilization and elimination of pathogenic bacteria. In this work, a two-dimensional Por-COF was constructed using 5,10,15,20-Tetrakis-(4-aminophenyl)-porphine-Zn(II) (Zn-TAPP) and Dihydroxyterephthalaldehyde (Dha), which was post-synthetically modified with silver nanoparticles (Ag NPs). Ag@ZnPor-COF delivered extraordinary photodynamic inactivation performance against Staphylococcus aureus and Escherichia coli under visible light (99.96 % and 99.75 %, respectively, within 20 min). The localized surface plasmon resonance of the Ag NPs enhanced the absorption of visible light whilst also aiding electron-hole separation, leading to efficient generation of reactive oxygen species (ROS), especially singlet oxygen (1O2). Further, the Ag NPs imparted Ag@ZnPor-COF with photothermal properties, thereby delivering even more effective control of pathogenic bacteria. Density functional theory (DFT) calculations validated the experimental findings, identifying Ag@ZnPor-COF as a potent antibacterial platform. Results encourage the wider use of Por-COFs and plasmonic nanomaterials in the development of antibacterial systems.

Porphyrin-based covalent organic framework as oxidase mimic for highly sensitive colorimetric detection of pesticides.

A covalent organic framework-based strategy was designedfor label-free colorimetric detection of pesticides. Covalent organic framework-based nanoenzyme with excellent oxidase-like catalytic activity was synthesized. Unlike other artificial enzymes, porphyrin-based covalent organic framework (p-COF) as the oxidase mimic showed highly catalytic chromogenic activity and good affinity toward TMB without the presence of H2O2, which can be used as substitute for peroxidase mimics and H2O2 system in the colorimetric reaction. Based on the fact that the pesticide-aptamer complex can inhibit the oxidase activity of p-COF and reduced the absorbance at 650nm in UV-Vis spectrum, a label-free and facile colorimetric detection of pesticides was designed and fabricated. Under the optimized conditions, the COF-based colorimetric probe for pesticide detection displayed high sensitivity and selectivity. Taking fipronil for example the limit of detection was 2.7ng/mL and the linear range was 5-500,000ng/mL. The strategy was successfully applied to the detection of pesticides with good recovery , which was in accordance with that of HPLC-MS/MS. The COF-based colorimetric detection was free of complicated modification H2O2, which guaranteed the accuracy and reliability of measurements. The COF-based sensing strategy is a potential candidate for the sensitive detection of pesticides of interests.

Biomimetic cascade intelligent paper chip sensor based on bimetallic porphyrin-based covalent organic framework with triple-enzyme mimetic activities

Enzyme-induced biological cascade catalysis can achieve selective and efficient transformations of substrates in vivo. Thus, the biomimetic cascade systems have attracted much attention in biological detection on account of their ingenious strategies for signal conduction and amplification. In this study, a porphyrin-based covalent organic framework (COFFe/CoP-Ph) with bimetal-nitrogen-coordinate centers (M − N4) were constructed via Schiff base reaction. The synergistic effect of the highly exposed M − N4 bimetallic active sites and the unique topology overcame the self-limitation of nanozyme, resulting in a significant enhancement of the triple-enzyme mimetic activities of COFFe/CoP-Ph, namely oxidase (OXD)-, peroxidase (POD)-, and catalase (CAT)-like activities. Simultaneously, a multiple enzyme-driven cascade catalysis strategy for signal amplification was proposed utilizing the OXD- and POD-like mimetic mechanisms of COFFe/CoP-Ph, enabling the colorimetric determination of malathion without the addition exogenous H2O2. The established colorimetric sensor exhibited an exceptional linear relationship within the range of 1–18 μM and a low detection limit of 11 nM. Subsequently, a portable smartphone platform was developed by integrating paper chip, facilitating successful malathion point-of-care testing (POCT) in real samples. This work not only creates a bimetallic COF nanozyme and establishes an efficient cascade amplification strategy, but also introduces a novel design approach for development of a low-cost and user-friendly POCT method.

Donor-acceptor covalent organic framework/ZnIn2S4 core-shell structure S-scheme heterostructure for efficient photocatalytic hydrogen evolution

Covalent organic frameworks (COFs) show promising prospect as the photocatalysts with advantages of exceptional light adsorption capability, large specific surface area, and adjustable band structure. However, COFs usually suffer from severe recombination of photogenerated carriers. Therefore, there is an urgent demand to design effective COF-based heterostructures to enhance the separation of carriers. In this work, a porphyrin-based COF with electron donor-acceptor structure is synthesized via condensation polymerization by using 5,10,15,20-tetrakis(4-aminophenyl)porphyrin (TAPPP) and N,N,N',N'-tetra(4-formylphenyl)benzidin (NFPBD) as the donor and acceptor, respectively. Subsequently, ZnIn2S4 (ZIS) are successfully in-situ grown on the surface of porphyrin-based COF, forming a novel core-shell structure. The in-situ synthesized ZIS with positive charges can be easily adsorbed on the negatively charged sites of the COF’s surface via the electrostatic interaction. This organic/inorganic hybrid COF-ZIS heterostructure exhibits a superior photocatalytic hydrogen evolution (PHE) rate of 695 μmol g−1 h−1, approximately three times higher than that of ZIS. The construction of COF-ZIS heterostructure plays an important role in enhancing the separation and transport of photogenerated carriers, which provides more electrons at the surface of ZIS to take part in proton reduction. Electron paramagnetic resonance spectra confirm the charge carriers transfer mode in the COF-ZIS heterostructure via an S-scheme mechanism. Moreover, upon loading Pt as the cocatalyst, the heterostructure achieves an effective PHE rate of 2711 μmol g−1 h−1 along with an exceptional stability. Additionally, the COF-ZIS heterostructure reaches up to 2.45% of apparent quantum efficiency at 400 nm. Notably, the average lifetime of the COF-ZIS heterostructure increases by 43.2% and 98.9% compared to that of ZIS and the COF individually, as observed through single-particle fluorescence spectroscopy. This work gives valuable inspiration into the building of donor-acceptor COF-based S-scheme heterostructures to achieve highly effective green energy conversion by aligning band structures.

Porphyrin-based covalent organic frameworks as doxorubicin delivery system for chemo-photodynamic synergistic therapy of tumors

Photodynamic therapy (PDT) is a non-invasive treatment method that has garnered significant attention in recent years. Nanoparticle-based drug delivery systems can achieve targeted drug release, thereby significantly reducing side effects and enhancing therapeutic efficacy. In this study, a covalent organic framework (COF) with an approximately spherical structure connected by azo bonds was synthesized. The synthesized COF was utilized as a hypoxia-responsive carrier for doxorubicin (DOX) drug delivery and was modified with hyaluronic acid (HA). DOX@COF@HA exhibited a reactive release under hypoxic conditions. Under normal oxygen conditions, the release of DOX was 16.9 %, increasing to 60.2 % with the addition of sodium hydrosulfite. In vitro experiments revealed that the group combining photodynamic therapy with chemotherapy exhibited the lowest survival rates for 4T1 and MHCC97-L cells. In vivo experiments further validated the effectiveness of combination therapy, resulting in a tumor volume of only 33 mm3 after treatment, with no significant change in mouse weight during the treatment period. DOX@COF@HA nanoplatforms exhibit substantial potential in tumor treatment.

Oxygen-tolerant CO2 electroreduction over covalent organic frameworks via photoswitching control oxygen passivation strategy

The direct use of flue gas for the electrochemical CO2 reduction reaction is desirable but severely limited by the thermodynamically favorable oxygen reduction reaction. Herein, a photonicswitching unit 1,2-Bis(5’-formyl-2’-methylthien-3’-yl)cyclopentene (DAE) is integrated into a cobalt porphyrin-based covalent organic framework for highly efficient CO2 electrocatalysis under aerobic environment. The DAE moiety in the material can reversibly modulate the O2 activation capacity and electronic conductivity by the framework ring-closing/opening reactions under UV/Vis irradiation. The DAE-based covalent organic framework with ring-closing type shows a high CO Faradaic efficiency of 90.5% with CO partial current density of −20.1 mA cm−2 at −1.0 V vs. reversible hydrogen electrode by co-feeding CO2 and 5% O2. This work presents an oxygen passivation strategy to realize efficient CO2 electroreduction performance by co-feeding of CO2 and O2, which would inspire to design electrocatalysts for the practical CO2 source such as flue gas from power plants or air.

Porphyrin-based covalent organic framework integrated with nitrogen doped carbon nanotube as electrode modifier for selective and simultaneous detection of hydroquinone and catechol with high sensitivity

A novel Co-porphyrin-based covalent organic framework (TT-COF(Co)) was synthesized and further integrated with nitrogen doped carbon nanotube (N-CNTs), which was used as electrode modifier material for the application in selective and simultaneous electrochemical detection of hydroquinone (HQ) and catechol (CA). The successful formation of TT-COF(Co)/N-CNTs nanocomposite was confirmed through a series of different characterization techniques, including scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Electrochemical results indicated that TT-COF(Co)/N-CNTs nanocomposite modified electrode had excellent sensing performance for HQ and CA in phosphate buffer, enabling selectively and simultaneously determination of these two dihydroxybenzene isomers. Under optimal testing conditions, linear calibration curves for the selective determination of HQ or CA in the presence of 30 µM of the corresponding isomers were obtained over the concentration range of 0.01–500 µM. The linear ranges for the simultaneous determination of HQ and CA were 0.003–300 µM, with detection limits of 0.81 nM for HQ and 0.74 nM for CA, respectively. The sensor also demonstrated satisfactory selectivity and stability, and was successfully used to analyse HQ and CA in real water samples. Our work made a useful contribution to strategical design of functionalized COFs materials for electrochemical sensing applications.

Indocyanine green-loaded porphyrin covalent organic frameworks for photothermal cancer therapy

A porphyrin-based covalent organic framework was synthesized as a platform for loading of indocyanine green. The resulting composites (ICG@COF NPs) exhibited enhanced photostability and superior photothermal effect, which demonstrated remarkable efficacy in tumor ablation in vivo.

Identification of two-dimensional covalent organic frameworks with mcm topology and their application in photocatalytic hydrogen evolution

Three porphyrin-based covalent organic frameworks (COFs) are synthesized. Their structures are exclusively composed of pentagonal pores, giving rise to mcm topology. The COFs exhibit high performance in photocatalytic hydrogen evolution from water.

Porphyrin-based covalent organic frameworks from design, synthesis to biological applications.

Covalent organic frameworks (COFs)constitutea class of highly functional porous materials composed of lightweight elements interconnected by covalent bonds, characterized by structural order, high crystallinity, and large specific surface area. The integration of naturally occurring porphyrin molecules, renowned for their inherent rigidity and conjugate planarity, as building blocks in COFs has garnered significant attention. This strategic incorporation addresses the limitations associated with free-standing porphyrins, resulting in the creation of well-organized porous crystal structures with molecular-level directional arrangements. The unique optical, electrical, and biochemical properties inherent to porphyrin molecules endow these COFs with diversified applications, particularly in the realm of biology. This review comprehensively explores the synthesis and modulation strategies employed in the development of porphyrin-based COFs and delves into their multifaceted applications in biological contexts. A chronological depiction of the evolution from design to application is presented, accompanied by an analysis of the existing challenges. Furthermore, this review offers directional guidance for the structural design of porphyrin-based COFs and underscores their promising prospects in the field of biology.

Vapor-Phase Synthesis of Electrocatalytic Covalent Organic Frameworks.

The inability to process many covalent organic frameworks (COFs) as thin films plagues their widespread utilization. Herein, a vapor-phase pathway for the bottom-up synthesis of a class of porphyrin-based COFs is presented. This approach allows integrating electrocatalysts made of metal-ion-containing COFs into the electrodes' architectures in a single-step synthesis and deposition. By precisely controlling the metal sites at the atomic level, remarkable electrocatalytic performance is achieved, resulting in unprecedentedly high mass activity values. How the choice of metal atoms, i.e., cobalt and copper, can determine the catalytic activities of POR-COFs is demonstrated. The theoretical data proves that the Cu site is highly active for nitrate conversion to ammonia on the synthesized COFs.

Fabrication of a polymer brush-functionalized porphyrin-based covalent organic framework for enrichment of N-glycopeptides.

A surface-initiated atom transfer radical polymerization method combining click chemistry was employed to prepare a novel porphyrin-based covalent organic framework composite grafted with polymer brushes (TAPBB@GMA@AMA@Cys) for the specific enrichment of N-glycopeptides. The material successfully realized the high efficiency enrichment of N-glycopeptides with good selectivity (1:1000), low detection limit (0.2 fmol/μL), and high loading capacity (133.3 mg·g-1). TheTAPBB@GMA@AMA@Cys was successfully applied to actual sample analysis; 235 N-glycopeptides related to 125 glycoproteins and 210 N-glycopeptides related to 121 glycoproteins were recognized from the serum of normal individuals and Alzheimer's disease patients, respectively. Gene ontology studies of molecular functions, cellular components, and biological processes have revealed that identified glycoproteins are strongly associated with neurodegenerative diseases involving innate immune responses, basement membranes, calcium binding, and receptor binding. The above results confirm the surprising potential of materials in glycoproteomics research and practical sample applications.

Turning on Singlet Oxygen Generation by Outer-Sphere Microenvironment Modulation in Porphyrinic Covalent Organic Frameworks for Photocatalytic Oxidation.

Singlet oxygen (1 O2 ) is ubiquitously involved in various photocatalytic oxidation reactions; however, efficient and selective production of 1 O2 is still challenging. Herein, we reported the synthesis of nickel porphyrin-based covalent organic frameworks (COFs) incorporating functional groups with different electron-donating/-withdrawing features on their pore walls. These functional groups established a dedicated outer-sphere microenvironment surrounding the Ni catalytic center that tunes the activity of the COFs for 1 O2 -mediated thioether oxidation. With the increase of the electron-donating ability of functional groups, the modulated outer-sphere microenvironment turns on the catalytic activity from a yield of nearly zero by the cyano group functionalized COF to an excellent yield of 98 % by the methoxy group functionalized one. Electronic property investigation and density-functional theory (DFT) calculations suggested that the distinct excitonic behaviors attributed to the diverse band energy levels and orbital compositions are responsible for the different activities. This study represents the first regulation of generating reactive oxygen species (ROS) based on the strategy of outer-sphere microenvironment modulation in COFs.

Photothermal porphyrin-based covalent organic framework for efficient removal of perfluoroalkyl substances

Temperature is vital to the removal ability of adsorbent materials. The application of convenient and energy-efficient light-induced heating to promote the removal of emerging contaminants is rarely reported. Here, we report synthesis of a photothermal porphyrin-based covalent organic framework (COF) called Por-MA for efficient removal of perfluoroalkyl substances (PFASs) in environment water. The crystalline Por-MA with rich nitrogen and ordered structure can provide electrostatic and hydrogen bonding interactions for adsorption of PFASs, further give a large adsorption capacity (686.6 mg g−1) and rapid adsorption kinetics (equilibrium time < 10 min) for perfluorooctanoic acid (PFOA) at 25 °C, outperforming several other COF-based sorbents. Moreover, endothermic adsorption of PFOA on Por-MA made promoting adsorption of PFASs on photothermal Por-MA with facile illumination possible. Removal efficiencies of PFASs on Por-MA in environmental water samples also significantly improved with LED irradiation, indicating the high potential of photothermal COFs for removal of contaminants in practical water.

Fabrication of boronic acid-functionalized covalent organic framework for the selective adsorption of cis-diol-containing compounds

In this work, we report a post-synthetic modification strategy to synthesize a boronic acid-functionalized porphyrin-based covalent organic framework (denoted as BA-COF) via the Suzuki-Miyaura cross-coupling reaction. Interestingly, BA-COF exhibits excellent selectivity in adsorbing cis-diol-containing compounds (CDC). The selective adsorption mechanism was addressed in detail, which is probably due to the boronate affinity from boronic acid group, hydrophilic interaction from the nitrogen-rich framework as well as “host–guest” interaction from the unique “trap” structure of porphyrin-based COF. The characterized results demonstrated its uniform morphology, large specific surface area, and excellent thermal stability. The adsorption kinetics demonstrated that the adenosine adsorption onto BA-COF conformed to the pseudo-second-order kinetic model and belonged to chemisorption. Based on the fitting of adsorption isotherms and thermodynamic analysis, the adenosine adsorption onto BA-COF was monomolecular layer adsorption and was a spontaneous endothermic reaction. Moreover, the reuse performance of BA-COF was investigated through consecutive adsorption–desorption cycle experiments. This work also demonstrates the potential of BA-COF for effective and selective adsorption of CDC in real sample.

Sensitive detection of Escherichia coli in diverse foodstuffs by electrochemical aptasensor based on 2D porphyrin-based COF.

The two-dimensional porphyrin-based covalent organic framework (denoted by Tph-TDC-COF) was used as the sensitive layerto build an aptamer-based electrochemical sensor for the detection of Escherichia coli (E.coli). Tph-TDC-COF produced with 5,10,15,20-tetrakis(4-aminophenyl)-21H, 23H-porphine (Tph) and [2,2'-bithiophene]-2,5'-dicarbaldehyde (TDC) as building blocks exhibited a highly conjugated structure, outstanding conductivity, large specific surface area, and strong bioaffinity towards aptamers. The adoption of Tph-TDC-COF-modified electrode resulted in improved sensing performance and increased anchoring affinity toward the E.coli-targeted aptamer. Under optimal conditions, the Tph-TDC-COF-based electrochemical aptasensor demonstrated an extremely low detection limit of 0.17CFUmL-1 for E.coli detection within a linear range of 10 to 1 × 108CFUmL-1, accompanied by good stability, excellent reproducibility and regeneration ability, and wide practical applications. The current electrochemical aptasensing technique has the potential to be extended to detect different foodborne bacteria using specific aptamer, therefore widening the application of COFs in biosensing and food safety fields.

Porphyrin-based covalent organic framework with self-accelerated M−N4 bimetallic active sites for enhanced electrochemical detection of trace hydrogen peroxide

The ultrasensitive detection of trace hydrogen peroxide (H2O2) has been a fascinating research topic owing to its significant application in environmental monitoring, food safety, and scientific research. In this study, bimetallic porphyrin-based covalent organic framework composites (MWCNTs@Mn/Fe-COF) was prepared by in situ polymerization of Mn porphyrin (MnPor) and Fe porphyrin (FePor) on multi-walled carbon nanotubes (MWCNTs), and a biomimetic enzyme electrochemical sensor was constructed for determination of trace H2O2. The unique topological structure features of COF and the high conductivity of MWCNTs not only ensured highly independent M−N4 electrochemical active sites, but also guaranteed efficient electron transfer pathways. Especially, the introduction of Mn sites formed a self-accelerated redox cycling between valence states, which significantly improved the electrocatalytic efficiency. Taking advantage of the above advantages, the MWCNTs@Mn/Fe-COF based sensor achieved ultrasensitive detection of H2O2 with a low detection limit of 2 nM. Moreover, the developed sensor has been successfully used to measure trace H2O2 induced by lab-equipped ultrasonic cleaners and in disinfector and apple juice. The constructed sensor in this study has potential application value in the rapid detection of trace H2O2 in real samples, which opened up a new way for the synthesis of bimetallic analog enzymes and the construction of ultra-sensitive electrochemical sensors.