Porphyrin-based Metal-organic Frameworks Research Articles

The low-temperature NO2 removal by tailoring metal node in porphyrin-based metal-organic frameworks

Nitrogen dioxide (NO2) is the most toxic and prevalent form of nitrogen oxides (NOx) pollutant and its removal from ambient air is a pressing challenge. The state-of-the-art deNOx technologies such as selective catalytic reduction (SCR) can only work at elevated temperatures (>250–300 °C), but ineffective for the NOx removal under ambient conditions. The adsorptive removal of NO2 is an alternative approach to SCR, whose success depends on the design of stable adsorbents capable of selectively capturing NO2 with a highly reversible capacity. Here we synthesized and developed five porphyrin-based metal-organic frameworks (PMOFs) as robust ambient NO2 adsorbents, including three aluminum-based (Al-PMOF) isostructures, and two zirconium-based (Zr-PMOFs) isostructures. Of them, Al-PMOF stands out to be the most promising candidate by showing the highest NO2 adsorption capacity (1.85 mmol/g), high stability, and good regenerability (retaining 87% capacity after five cycles of adsorption) at dry conditions. The NO2 adsorption capacity of Al-PMOF was approximately doubled (3.61 mmol/g) at wet conditions. In situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) revealed the NO2 adsorption mechanism – the hydrogen bonding occurs between bridging hydroxyl (-OH) (attached to the metal node) and NO2 molecules. Our work demonstrates that PMOFs are promising NO2 adsorbents and will provide guidance for designing robust and reusable adsorbents for efficiently removing NO2 at ambient temperature.

"Switch-on" fluorescence sensing platform based on porphyrin metal-organic frameworks for rapid and specific detection of zinc ion.

Zinc ion (Zn2+) is a necessary transition metal ion in the human body and plays a vital role in biological systems. Therefore, it is meaningful for rapid, sensitive, and specific detection of Zn2+. Herein, a "switch-on" fluorescence sensing platform for the detection of Zn2+ was successfully established. In this work, we report an optical nanoprobe with amino functional groups based on porphyrin metal-organic frameworks (PCN-NH2) through a simple treatment method. The modification of the salicylaldehyde (SA) through the C=N acts as a quencher of PCN-NH2 and the ligand of Zn2+ can effectively inhibit the fluorescence emission of PCN-NH2. The complex of porphyrin-based metal-organic framework and salicylaldehyde (PCN/SA) acts as the fluorescence sensing probe. The presence of Zn2+ results in the new emission peak at 448 nm due to the formation of a complex between Zn2+ and SA. The corresponding fluorescence signal changes were used to accurately detect the concentration of Zn2+. The fluorescence sensing platform shows advantages, including rapid response, high sensitivity, and excellent specificity with a linear detection range of Zn2+ between 0.1 and 250 μM, and a low detection limit (LOD) of 0.07 μM. And the feasibility of the method was verified for the quantification of Zn2+ in cell lysate, environmental water, and plasma.

Enhancing the Antitumor Effect of Doxorubicin with Photosensitive Metal-Organic Framework Nanoparticles against Breast Cancer.

Breast cancer is one of the most common malignant tumors in women. The existence of multiple breast cancer subtypes often leads to chemotherapy failure or the development of drug resistance. In recent years, photodynamic therapy has been proven to enhance the sensitivity of tumors to chemotherapeutic drugs. Porphyrin-based metal-organic framework (MOF) materials could simultaneously be used as carriers for chemotherapy and photosensitizers in photodynamic therapy. In this paper, doxorubicin hydrochloride (DOX) was loaded in porphyrin MOFs, and the mechanism of the synergistic effect of the DOX carriers and photodynamic therapy on breast cancer was investigated. In vitro and in vivo experiments have shown that MOFs could prolong the residence time of DOX in tumor tissues and promote the endocytosis of DOX by tumor cells. In addition, adjuvant treatment with photodynamic therapy can promote breast cancer tumors to resensitize to DOX and synergistically enhance the chemotherapy effect of DOX. Therefore, this study can provide effective development ideas for reversing drug resistance during breast cancer chemotherapy and improving the therapeutic effect of chemotherapy on breast cancer.

Role of Zr6 Metal Nodes in Zr-Based Metal-Organic Frameworks for Catalytic Detoxification of Pesticides.

Pesticides are chemicals widely used for agricultural industry, despite their negative impact on health and environment. Although various methods have been developed for pesticide degradation to remedy such adverse effects, conventional materials often take hours to days for complete decomposition and are difficult to recycle. Here, we demonstrate the rapid degradation of organophosphate pesticides with a Zr-based metal-organic framework (MOF), showing complete degradation within 15 min. MOFs with different active site structures (Zr node connectivity and geometry) were compared, and a porphyrin-based MOF with six-connected Zr nodes showed remarkable degradation efficiency with half-lives of a few minutes. Such a high efficiency was further confirmed in a simple flow system for several cycles. This study reveals that MOFs can be highly potent heterogeneous catalysts for organophosphate pesticide degradation, suggesting that coordination geometry of the Zr node significantly influences the catalytic activity.

Understanding disorder and linker deficiency in porphyrinic zirconium-based metal\u2013organic frameworks by resolving the Zr8O6 cluster conundrum in PCN-221

Porphyrin-based metal–organic frameworks (MOFs), exemplified by MOF-525, PCN-221, and PCN-224, are promising systems for catalysis, optoelectronics, and solar energy conversion. However, subtle differences between synthetic protocols for these three MOFs give rise to vast discrepancies in purported product outcomes and description of framework topologies. Here, based on a comprehensive synthetic and structural analysis spanning local and long-range length scales, we show that PCN-221 consists of Zr6O4(OH)4 clusters in four distinct orientations within the unit cell, rather than Zr8O6 clusters as originally published, and linker vacancies at levels of around 50%, which may form in a locally correlated manner. We propose disordered PCN-224 (dPCN-224) as a unified model to understand PCN-221, MOF-525, and PCN-224 by varying the degree of orientational cluster disorder, linker conformation and vacancies, and cluster–linker binding. Our work thus introduces a new perspective on network topology and disorder in Zr-MOFs and pinpoints the structural variables that direct their functional properties.

Atomically Dispersed Iron Metal Site in a Porphyrin-Based Metal-Organic Framework for Photocatalytic Nitrogen Fixation.

The rational design of photocatalysts for efficient nitrogen (N2) fixation at ambient conditions is important for revolutionizing ammonia production and quite challenging because the great difficulty lies in the adsorption and activation of the inert N2. Inspired by a biological molecule, chlorophyll, featuring a porphyrin structure as the photosensitizer and enzyme nitrogenase featuring an iron (Fe) atom as a favorable binding site for N2via π-backbonding, here we developed a porphyrin-based metal-organic framework (PMOF) with Fe as the active center as an artificial photocatalyst for N2 reduction reaction (NRR) under ambient conditions. The PMOF features aluminum (Al) as metal node imparting high stability and Fe incorporated and atomically dispersed by residing at each porphyrin ring promoting the adsorption and the activation of N2, termed Al-PMOF(Fe). Compared with the pristine Al-PMOF, Al-PMOF(Fe) exhibits a substantial enhancement in NH3 yield (635 μg g-1cat.) and production rate (127 μg h-1 g-1cat.) of 82% and 50%, respectively, on par with the best-performing MOF-based NRR catalysts. Three cycles of photocatalytic NRR experimental results corroborate a stable photocatalytic activity of Al-PMOF(Fe). The combined experimental and theoretical results reveal that the Fe-N site in Al-PMOF(Fe) is the active photocatalytic center that can mitigate the difficulty of the rate-determining step in photocatalytic NRR. The possible reaction pathways of NRR on Al-PMOF(Fe) were established. Our study of porphyrin-based MOF for the photocatalytic NRR will provide insight into the rational design of catalysts for artificial photosynthesis.

Biomimetic sonodynamic therapy-nanovaccine integration platform potentiates Anti-PD-1 therapy in hypoxic tumors

Immune checkpoint blockade (ICB) therapy has emerged as novel therapeutic modality for hard-to-treat solid tumors. However, inadequate T cell infiltration in hypoxic solid tumors limits its anticancer efficacy. Here we develop a sonodynamic therapy (SDT)-nanovaccine integration platform constructed by binding a manganese porphyrin-based metal-organic frameworks (Mn-MOF) with an immune adjuvant CpG and then coating with cell membranes derived from ovalbumin (OVA)-overexpressing melanoma B16 cells (cMn-MOF@CM) for potentiating anti-programmed death receptor 1 (PD-1) antibody in malignant melanoma therapy. cMn-MOF@CM with prolonged blood circulation and enhanced tumor targeting efficiently relieves tumor hypoxia and generates strong SDT effects and immunogenic cell death. The tumor-associated antigens both in situ derived from SDT and OVA exhibit vaccine-like functions together with the immune adjuvant CpG, eliciting a strong tumor-specific immune response by promoting DC maturation and T cell activation. Importantly, the combination of cMn-MOF@CM-triggered SDT and anti-PD-1 antibody induces stronger systemic immune response and long-term immunological memory function to prevent tumor growth and recurrence. These findings reveal that cMn-MOF@CM with US irradiation may be a potential candidate to potentiate ICB therapy for hypoxic cancer therapy.

Porphyrin MOF-Derived Porous Carbons: Preparation and Applications

Metal–organic frameworks (MOFs) are crystalline materials with permanent porosity, composed of metal nodes and organic linkers whose well-ordered arrangement enables them to act as ideal templates to produce materials with a uniform distribution of heteroatom and metal elements. The hybrid nature of MOFs, well-defined pore structure, large surface area and tunable chemical composition of their precursors, led to the preparation of various MOF-derived porous carbons with controlled structures and compositions bearing some of the unique structural properties of the parent networks. In this regard, an important class of MOFs constructed with porphyrin ligands were described, playing significant roles in the metal distribution within the porous carbon material. The most striking early achievements using porphyrin-based MOF porous carbons are here summarized, including preparation methods and their transformation into materials for electrochemical reactions.

Tunable dielectric performance of porphyrin based metal−organic frameworks with polar molecule confinement

With the rapid development of 5G communications, the designs of metal-organic frameworks (MOFs) with high porosity, tunable structural features as well as low dielectric constant have been gradually focused and developed with potential to be used as an interlayer dielectric (ILD) material in integrated circuits (IC). In this work, porphyrin based metal-organic frameworks (AlOH)2H2TCPP, denoted as Al-TCPP-MOFs, were synthesized by hydrothermal reaction. The structural, thermal and dielectric properties of Al-TCPP-MOFs, Al-TCPP-MOFs-H2O (polar water molecular confinement on Al-TCPP-MOFs), and Al-TCPP-MOFs-DMF (polar DMF molecular confinement on Al-TCPP-MOFs) were characterized systematically. The results showed that the Al-TCPP-MOFs material exhibited high porosity, as well as uniform lamellar structure. The role of polar molecular confinement effect of different coordination systems on the dielectric performances of MOFs were investigated, and the relative dielectric constant of Al-TCPP-MOFs was found to be as low as 2.3 at 103 Hz. Moreover, the Al-TCPP-MOFs exhibited excellent stability of dielectric properties under a wide temperature range and reliable thermal stability up to 420 °C. The preparation of low dielectric constant porphyrin-based metal–organic framework with a high thermal stability opens up a new direction for the application of MOFs in electronic devices of 5G era.

Recent advances in porphyrin-based MOFs for cancer therapy and diagnosis therapy

This review covers not only diverse constructions of porphyrin-based MOFs, but also the various therapeutic approaches and multiple biomedical applications. • A brief introduction of the biomedical advantages of porphyrin-based MOFs is provided in this review. • Porphyrin-based MOFs with diverse synthetic methods are introduced. • Various therapeutic modalities of porphyrin-based MOFs are given and discussed. • Bioimaging applications of porphyrin-based MOFs are described in detail. • The challenges and development prospects of porphyrin-based MOFs are presented. Porphyrins and porphyrin derivatives have attracted significant interest in the fields of catalysis, biosensing, gas storage, solar cells, and biomedical applications owing to their outstanding photophysical and electrochemical properties. Nevertheless, their biological application especially in the therapy and diagnosis of cancer is severely hindered by certain inherent limitations such as self-quenching, weak absorption in the biological spectral window, and poor chemical and optical stability. Porphyrin-based metal organic frameworks (MOFs), a family of novel hybrid porous coordination polymers, have been developed to overcome the limitations of porphyrins and enable their biomedical applications. Porphyrin-based MOFs are constructed using metal ions or clusters and porphyrin ligands through a self-assembly process. Porphyrin-based MOFs maintain the specific properties of porphyrins and can be loaded or modified with functional molecules or drugs to impart therapeutic and imaging abilities. In this review, we discuss the different synthetic approaches of porphyrin-based MOFs and examine the current developments and achievements of porphyrin-based MOFs in the field of biomedical applications, especially cancer therapy and bioimaging in detail. Finally, we discuss the challenges in the biomedical applications of porphyrin-based MOFs and present possible research directions to achieve highly efficient therapeutic effects and high-quality imaging for cancer theranostics.

Engineering the electronic and optical properties of 2D porphyrin-paddlewheel metal-organic frameworks

Metal-organic frameworks (MOFs) are promising photocatalytic materials due to their high surface area and tuneability of their electronic structure. We discuss here how to engineer the band structures and optical properties of a family of two-dimensional porphyrin-based MOFs, consisting of M-tetrakis(4-carboxyphenyl)porphyrin structures (M-TCPP, where M = Zn or Co) and metal (Co, Ni, Cu or Zn) paddlewheel clusters, with the aim of optimising their photocatalytic behaviour in solar fuel synthesis reactions (water-splitting and/or CO2 reduction). Based on density functional theory (DFT) and time-dependent DFT simulations with a hybrid functional, we studied three types of composition/structural modifications: (a) varying the metal centre at the paddlewheel or at the porphyrin centre to modify the band alignment; (b) partially reducing the porphyrin unit to chlorin, which leads to stronger absorption of visible light; and (c) substituting the benzene bridging between the porphyrin and paddlewheel, by ethyne or butadiyne bridges, with the aim of modifying the linker to metal charge transfer behaviour. Our work offers new insights on how to improve the photocatalytic behaviour of porphyrin- and paddlewheel-based MOFs.

High selective photocatalytic CO2 conversion into liquid solar fuel over a cobalt porphyrin-based metal-organic framework.

In the present study, porphyrin-based metal-organic framework (Co/PMOF) was synthesized and characterized by different spectra analyses. The photoluminescence properties of porphyrin and Co/PMOF revealed that the photoluminescence of Co/PMOF was quenched compared to the porphyrin, indicating that the lifetime of photo-generated charge carriers in Co/PMOF is longer than porphyrin. The prepared Co/PMOF was applied as an efficient photocatalyst for CO2 photoconversion to formate in the presence of triethanolamine (TEOA) as a sacrificial agent under visible-light irradiation. The photoreaction results showed that 23.21µmol HCOO- was produced over Co/PMOF during the 6h photocatalytic reaction under visible illumination, showing much better activity than the porphyrin, 4.56µmol HCOO-. No other products were detected, suggesting that this reaction over Co/PMOF has high selectivity. Co/PMOF reusability and stability were examined through recycling tests and there were no remarkable losses of photoactivity even after three cycles of photoreaction. Moreover, FTIR measurement and UV-Vis spectra demonstrated no notable changes in Co/PMOF structure. As a result, superior photocatalytic behavior of Co/PMOF was implied for CO2 photoreduction which highlights the great potential of assembly porphyrin and cobalt into MOFs for CO2 photoreduction.

Achieving synergistically enhanced dual-mode electrochemiluminescent and electrochemical drug sensors via a multi-effect porphyrin-based metal-organic framework

Abstract Since the sensing methods in drug detection are commonly hampered by signal capacity limitations and sole analysis information, dual-mode sensors with high accuracy and flexibility have become more popular. Herein, we present a two-dimensional porphyrin-based metal-organic framework (ZnTCPP MOF) as a unique electrochemiluminescent (ECL) and electrochemical (EC) dual-signal indicator, combined with L-penicillamine-capped Au nanoparticles (L-Pen-Au NPs) as a specific selector, to construct an innovative dual-mode drug sensing platform. Inspired by the optical and electrocatalytic activity of 5,10,15,20-tetrakis-(4-carboxyphenyl)porphyrin (TCPP), a series of ZnTCPP MOFs have been synthesized through a facile bottom-up method. Among them, the “oval-like” ZnTCPP MOF generates higher ECL responses than TCPP monomer when acting as a near-infrared luminophore and outputs stronger EC signals when acting as a redox active probe. In addition, the ZnTCPP MOF, when employed as a nanocarrier, can load many L - Pen-Au NPs. Using L-Pen-Au NPs as selectors, synergistically enhanced dual-mode sensors for detection of the anti-inflammatory drug S-naproxen (S-NAP) exhibit versatile and superior performance and a wide linear range with an ultralow limit of detection. We believe that the applications of this dual-mode sensor can be readily expanded to become a universal platform for sensitive detection of different types of drugs by changing the selector.

A Bio-Conjugated Chlorin-Based Metal-Organic Framework for Targeted Photodynamic Therapy of Triple Negative Breast and Pancreatic Cancers.

The field of photodynamic therapy (PDT) has continued to show promise as a potential method for treating tumors. In this work a photosensitizer (PS) has been delivered to cancer cell lines for PDT by incorporation into the metal-organic framework (MOF) as an organic linker. By functionalizing the surface of MOF nanoparticles with maltotriose the PS can efficiently target cancer cells with preferential uptake into pancreatic and breast cancer cell lines. Effective targeting overcomes some current problems with PDT including long-term photosensitivity and tumor specificity. Developing a PS with optimal absorption and stability is one of the foremost challenges in PDT and the synthesis of a chlorin which is activated by long-wavelength light and is resistant to photo-bleaching is described. This chlorin-based MOF shows anti-cancer ability several times higher than that of porphyrin-based MOFs with little toxicity to normal cell lines and no dark toxicity.

Porphyrin-Based Metal-Organic Framework Probe: Highly Selective and Sensitive Fluorescent Turn-On Sensor for M3+ (Al3+, Cr3+, and Fe3+) Ions.

The development of porphyrin-based metal-organic frameworks (MOFs) has attracted significant interest in the scientific community in recent years because of their versatile applications particularly in optical and electronic fields. In this study, a highly selective and sensitive fluorescent turn-on sensor using a porphyrinic MOF, Tb-TCPP, is presented, which displays a 10-fold fluorescence enhancement in the presence of Al3+, Cr3+, and Fe3+ ions. The detection limit is in the nM region. For the Al3+ ion, it could be visually detected at concentrations as low as 5 mM within 15 min. Tb-TCPP could also be used as an indicator for acidic or alkaline solutions at pH values of >9 and <3. The studies on the detection mechanism illustrate that cation exchange proceed between Tb-TCPP and these M3+ ions, and consequently, energy transfer from TCPP to Tb3+ is suppressed and π*-π energy transfer of the porphyrin ligand is significantly enhanced.

Porphyrin based metal–organic frameworks: highly sensitive materials for optical sensing of oxygen in gas phase

Luminescence of PCN-224-based MOFs is efficiently quenched by molecular oxygen making them promising for optical sensing of oxygen in the gas phase.

Potassium Ferrate-loaded Porphyrin-based (VI) Metal-organic Frameworks for Combined Photodymanic and Chemodynamic Tumor Therapy

Potassium Ferrate-loaded Porphyrin-based (VI) Metal-organic Frameworks for Combined Photodymanic and Chemodynamic Tumor Therapy

The fluorescence imaging and precise suppression of bacterial infections in chronic wounds by porphyrin-based metal-organic framework nanorods.

Nano-antibacterial agents can play a critical role in chronic wound management. However, the design of an intelligent nanosystem that can provide both a visual warning of infection and precise sterilization remains a hurdle. Herein, a rod-like porphyrin-based metal-organic framework theranostic nanosystem (Zn-TCPP nanorods) is fabricated via coordination chelation between tetrakis(4-carboxylphenyl)porphyrin and zinc ions. This system can show significant fluorescence activation in response to the local elevated pH shown by chronic wounds, a main indicator of wound infection. Meanwhile, under the guidance of fluorescence imaging, the highly spatiotemporally precise photodynamic inactivation of microorganisms can be carried out without the destruction of surrounding normal cells and nascent cells. The results demonstrated that the Zn-TCPP nanorods were a highly sensitive and reversible probe for sensing alkaline pH levels. Alterations in the fluorescence of the Zn-TCPP nanorods can accurately indicate the infection status and heterogeneity of infection within the wound bed. Under specific light irradiation, the Zn-TCPP nanorods can exterminate 97% of Staphylococcus aureus via the generation of reactive oxygen species (ROS). Assays of extensive wounds demonstrate that the precise fluorescence-imaging-guided suppression of bacterial infection can significantly reduce the mouse mortality rate and accelerate wound healing. This system provides the opportunity for "precision medicine" relating to chronic wounds and some large-area wounds.

A photosensitive metal-organic framework having a flower-like structure for effective visible light-driven photodegradation of rhodamine B.

Porphyrin-based metal–organic frameworks (MOFs) have great photocatalytic potential due to their good photosensitivity. Their photocatalytic performance is not only determined by molecular structure but also by morphology. Flower-like MOFs are considered to be good materials for catalysis due to their larger specific surface area, more exposed active sites, and good stability. Here, we first proposed a method to synthesize flower-like porphyrin-based MOFs using trifluoroacetic acid as a morphology control agent. These MOFs had a large BET surface area (605.04 m2 g−1), a stable structure and a complete morphology. Meanwhile, we discussed their self-assembly process and mechanism in detail. In addition, we studied the photocatalytic performance of flower-like porphyrin-based MOFs and found that the flower-like Cu-TCPP (TCPP = tetrakis(4-carboxyphenyl)porphyrin) has excellent photocatalytic activity. Its photodegradation efficiency toward the cationic dye rhodamine B reached 88% within 100 min and the sample still maintained its stable catalytic activity and complete flower-like morphological structure after five repeated uses. Furthermore, this synthetic strategy can be extended to control the morphology of other MOFs.

Manganese porphyrin-based metal-organic framework for synergistic sonodynamic therapy and ferroptosis in hypoxic tumors.

Development of efficient therapeutic strategy to incorporate ultrasound (US)-triggered sonodynamic therapy (SDT) and ferroptosis is highly promising in cancer therapy. However, the SDT efficacy is severely limited by the hypoxia and high glutathione (GSH) in the tumor microenvironment, and ferroptosis is highly associated with reactive oxygen species (ROS) and GSH depletion.Methods: A manganese porphyrin-based metal-organic framework (Mn-MOF) was constructed as a nanosensitizer to self-supply oxygen (O2) and decrease GSH for enhanced SDT and ferroptosis. In vitro and in vivo analysis, including characterization, O2 generation, GSH depletion, ROS generation, lipid peroxidation, antitumor efficacy and tumor immune microenvironment were systematically evaluated.Results: Mn-MOF exhibited catalase-like and GSH decreasing activity in vitro. After efficient internalization into cancer cells, Mn-MOF persistently catalyzed tumor-overexpressed H2O2 to in-situ produce O2 to relieve tumor hypoxia and decrease GSH and GPX4, which facilitated the formation of ROS and ferroptosis to kill cancer cells upon US irradiation in hypoxic tumors. Thus, strong anticancer and anti-metastatic activity was found in H22 and 4T1 tumor-bearing mice after a single administration of Mn-MOF upon a single US irradiation. In addition, Mn-MOF showed strong antitumor immunity and improved immunosuppressive microenvironment upon US irradiation by increasing the numbers of activated CD8+ T cells and matured dendritic cells and decreaing the numbers of myeloid-derived suppressor cells in tumor tissues.Conclusions: Mn-MOF holds great potential for hypoxic cancer therapy.