Porphyrin-based Covalent Organic Frameworks Research Articles

A nickel porphyrin-based covalent organic framework modified electrode for the electrochemical detection of acetaminophen.

Covalent organic frameworks (COFs) can be rationally designed with functional organic ligands to improve the electrochemical responsiveness of the electrode toward certain medicinal compounds. In this study, we synthesized a COF-Ni electrocatalyst material, which is formed by covalent coupling of electron-rich 2,3,6,7-tetrakis (4-formylphenyl) tetrakis (4-imidazolyl) (TTF-4CHO) and hole-rich 5,10,15,20-tetrakis (4-aminophenyl) porphyrin nickel(II) (TAPP-Ni). The reasonable electron transfer path design, the large specific surface area of the COF and the physical properties of ordered nanopores, as well as the Ni-N4 bond as a highly active catalytic center, allow the COF-Ni material modified electrode to exhibit excellent sensing performance for acetaminophen (ACOP). The detection limit for ACOP is as low as 47.6 nM, with a linear range of 1-1500 μM, which is better than for most of the reported sensors. With superior interference resistance and good stability performance, COF-Ni is a highly suited electrode modification material for real-world sample detection, which provided a new perspective for application of COF materials in drug analysis.

COFs functionalized self-cleaning loose nanofiltration membranes for efficient dye/salt separation

In spite of the fact that loose nanofiltration membrane (LNFM) technology has certified inspiring prospects in the remediation of dyestuff-comprising wastewater, omnipresent membrane fouling deteriorates its separation competence and hinders its practical application. Herein, a neoteric LNFM with finely tuned anti-fouling and self-cleaning properties was manufactured via the reformative phase inversion procedure integrated with the correctional interfacial polymerization process. By altering the casting solution (i.e., adding nano additives) and coagulation bath (i.e., applying melamine aqueous solution rather than pure water) recipes, the porphyrin-based covalent organic framework (COF-366) and melamine monomers were introduced into the polymeric matrix ingeniously in one step, participating the subsequent interfacial polymerization reaction straightly. The COF-366 with photocatalytic degradation performance and hydrophilicity bestows the resultant LNFM with superior decomposing capacity for organic micro-pollutants under visible light irradiation and better operation durability. Moreover, this substrate-confined amine diffusion combined with the high polarity of melamine enables the formation of a thinner nanofilm for easy mass transport. The best-performing LNFM invented in this work exhibited a high water permeance up to 65 L m−2 h−1 bar−1, excellent dye retention (95.7 % against methyl blue), and salt/dye discrimination (27.1 for methyl blue and Na2SO4 selectivity) abilities. Eventually, the membrane could recover to original separation efficacy after the cyclic degradation testing. Overall, this work demonstrates an extensive perspective to pioneer an advanced self-cleaning membrane for dye/salt fractionation.

Selective Generation of Reactive Oxygen Species in Photocatalytic Oxidation by Tuning Porphyrin-Based COFs' Dimensionality.

Regulating the selective generation of reactive oxygen species (ROS) is a significant challenge in the field of photocatalytic oxidation, with successful approaches still being limited. Herein, we present a strategy to selectively generate singlet oxygen (1O2) and superoxide radicals (O2•-) by tuning the dimensionality of porphyrin-based covalent organic frameworks (COFs). The transformation of COFs from three-dimensional (3D) solids to two-dimensional (2D) sheets was achieved through the reversible protonation of the imine bond. Upon irradiation, both bulk and thin-layer COF-367 can transfer energy to O2 to generate 1O2. However, thin-layer COF-367 exhibited a superior performance compared to its bulk counterpart in activating O2 to form the O2•- radicals via electron transfer. After excluding the influences of the band structure, O2 adsorption energy, and frontier orbital composition attributed to the dimensionality of the COFs, it is reasonably speculated that the variance in ROS generation arises from the differential exposure ratios of the active surfaces, leading to distinct reaction pathways between the carrier and O2. This study is the first to explore the modulation mechanism of COF dimensionality on the activation of the O2 pathway, underscoring the importance of considering COF dimensionality in photocatalytic reactions.

Electrocatalyst with a covalent organic framework and conducting skeleton for simultaneous determination of adenine and guanine

In this study, we integrated Cu porphyrin-based covalent organic frameworks (TTCOF-Cu) with high-activity CuNC centers and conductive backbone-functionalized carbon nanotubes (NH2-CNTs). The obtained NH2-CNTs@TTCOF-Cu composites exhibited a unique structure, and the bonding of TTCOF-Cu to NH2-CNTs allowed their in situ growth, which demonstrated high conductivity and more active sites. Consequently, well-separated and defined oxidation peaks for guanine (G) and adenine (A) were presented by differential pulse voltammetry (DPV) at NH2-CNTs@TTCOF-Cu modified electrode, and high sensitivity and selectivity were also achieved. The linear range for detecting G and A was 0.05–200 μM, respectively, and the detection limits for G and A were as low as 0.0163 and 0.0155 μM. It was also successfully applied to the analysis of G and A in heat-denatured herring sperm DNA samples.

Robust Imidazole-Linked Covalent Organic Framework Enabling Crystallization Regulation and Bulk Defect Passivation for Highly Efficient and Stable Perovskite Solar Cells.

The low crystallinity of the perovskite layers and many defects at grain boundaries within the bulk phase and at interfaces are considered huge barriers to the attainment of high performance and stability in perovskite solar cells (PSCs). Herein, a robust photoelectric imidazole-linked porphyrin-based covalent organic framework (PyPor-COF) is introduced to precisely control the perovskite crystallization process and effectively passivate defects at grain boundaries through a sequential deposition method. The 1D porous channels, abundant active sites, and high crystallization orientation of PyPor-COF offer advantages for regulating the crystallization of PbI2 and eliminating defects. Moreover, the intrinsic electronic characteristics of PyPor-COF endow a more closely matched energy level arrangement within the perovskite layer, which promotes charge transport and thereby suppresses the recombination of photogenerated carriers. The champion PSCs containing PyPor-COF achieved power conversion efficiencies of 24.10% (0.09 cm2) and 20.81% (1.0 cm2), respectively. The unpackaged optimized device is able to maintain its initial efficiency of 80.39% even after being exposed to air for 2000 h. The device also exhibits excellent heating stability and light stability. This work gives a new impetus to the development of highly efficient and stable PSCs via employing COFs.

Photoactive Porphyrin-Based Covalent Organic Frameworks for Photocatalytic Applications

The incorporation of porphyrin units into covalent organic frameworks (COFs) brings new photoelectrochemical properties to the resulted systems. We have developed a bottom-up strategy to prepare a series of tailor-made chiral COFs. The porphyrin subunits act as antennae to harvest visible light. Meanwhile, various secondary amine-based chiral functional groups are immobilized on the pore walls of COFs as catalytic sites. As a result, the COFs that are elaborately designed to merge photoactive building blocks and chiral catalytic sites achieve high production yields with good enantiomeric excess in photocatalytic asymmetric alkylation of aldehydes. In further studies, we have also prepared isostructural porphyrin-based COFs with high crystallinity and porosity, and investigated their photocatalytic N2 fixation performance. The porphyrin building blocks act as not only light-harvesting antennae, but also docking sites for anchoring Au single atoms. Moreover, the microenvironment of Au sites and optoelectronic properties of photocatalysts could be finely tuned by designing the functional groups on proximal and distal position of porphyrin units. The structure-activity relationship has been studied in detail by combining experimental results and theoretical calculations. The introduction of electron-withdrawing groups facilitates the separation and transportation of photogenerated electrons within the entire framework, thus promoting the adsorption of N2 on Au sites for achieving high performance of N2 conversion into NH3.

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.

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.