Porphyrinic Metal-organic Framework Research Articles

Porphyrinic Zirconium Metal-Organic Frameworks (MOFs) as Heterogeneous Photocatalysts for PET-RAFT Polymerization and Stereolithography.

In this study, porphyrinic zirconium (Zr) MOFs were investigated as heterogeneous photocatalysts for photoinduced electron transfer-reversible addition-fragmentation chain transfer (PET-RAFT) polymerization of various monomers under a broad range of wavelengths, producing polymers with high monomer conversions, narrow molecular weight distributions, low dispersity and good chain-end fidelity. Screening of various porphyrinic Zr-MOFs (Zn) containing Zn-metalled porphyrinic ligands demonstrated that MOF-525 (Zn) with the smallest size had the best photocatalytic activity in PET-RAFT polymerization, due to enhanced dispersion and light penetration. Oxygen tolerance and temporal control were also demonstrated during MOF catalysed PET-RAFT. Results suggested that the polymerization rates were significantly affected by changing the size and surface area of MOFs, and the heterogeneous MOF photocatalysts could be easily separated and recycled for up to five independent PET-RAFT polymerizations without an obvious decrease in efficiency. Finally, the MOF photocatalysts were utilized to create three-dimensional polymeric objects with high resolution via visible light mediated stereolithography in an open-air environment.

Rapid Exciton Migration and Amplified Funneling Effects of Multi-Porphyrin Arrays in a Re(I)/Porphyrinic MOF Hybrid for Photocatalytic CO2 Reduction.

A porphyrinic metal-organic framework (PMOF) known as PCN-222(Zn) was chemically doped with a molecular Re(I) catalyst-bearing carboxylate anchoring group to form a new type of metal-organic framework (MOF)-Re(I) hybrid photocatalyst. The porphyrinic MOF-sensitized hybrid (PMOF/Re) was prepared with an archetypical CO2 reduction catalyst, (L)ReI(CO)3Cl (Re(I); L = 4,4'-dicarboxylic-2,2'-bipyridine), in the presence of 3 vol % water produced CO with no leveling-off tendency for 59 h to give a turnover number of ≥1893 [1070 ± 80 μmol h-1 (g MOF)-1]. The high catalytic activity arises mainly from efficient exciton migration and funneling from photoexcited porphyrin linkers to the peripheral Re(I) catalytic sites, which is in accordance with the observed fast exciton (energy) migration (≈1 ps) in highly ordered porphyrin photoreceptors and the effective funneling into Re(I) catalytic centers in the Re(I)-doped PMOF sample. Enhanced catalytic performance is convincingly supported by serial photophysical measurements including decisive Stern-Volmer interpretation.

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.

Assembled Exciton Dynamics in Porphyrin Metal-Organic Framework Nanofilms.

Metal-organic frameworks (MOFs) provide a novel strategy to precisely control the alignment of molecules to enhance exciton diffusion for high-performance organic semiconductors. In this paper, we characterize exciton dynamics in highly ordered and crystalline porphyrin MOF nanofilms by time-resolved photoluminescence and femtosecond-resolved transient absorption spectroscopy. Results suggest that porphyrin MOF nanofilms could be a promising candidate for high-performance organic photovoltaic semiconductors in which the diffusion coefficient and diffusion length of excitons are 9.0 × 10-2 cm2 s-1 and 16.6 nm, respectively, comparable with or even beyond that of other excellent organic semiconductors. Moreover, by monitoring real-time exciton dynamics it is revealed that excitons in MOF nanofilms undergo high-efficient intermolecular hopping and multiexciton annihilation due to the short intermolecular distance and aligned molecular orientation in MOF structure, thus providing new insights into the underlying physics of exciton dynamics and many-body interaction in molecular assembled systems.

Porphyrin and phthalocyanine-based metal organic frameworks beyond metal-carboxylates.

Given the ubiquitous role of porphyrins in natural systems, these molecules and related derivatives such as phthalocyanines are fascinating building units to achieve functional porous materials. Porphyrin-based MOFs have been developed over the past three decades, yet chemically robust frameworks, necessary for applications, have been achieved much more recently and this field is expanding. This progress is partially driven by the development of porphyrins and phthalocyanines bearing alternative coordinating groups (phosphonate, azolates, phenolates…) that allowed moving the related MOFs beyond metal-carboxylates and achieving new topologies and properties. In this perspective article we first give a brief outline of the synthetic pathways towards simple porphyrins and phthalocyanines bearing these complexing groups. The related MOF compounds are then described; their structural and textural properties are discussed, as well as their stability and physical properties. An overview of the resulting nets and topologies is proposed, showing both the similarities with metal-carboxylate phases and the peculiarities related to the alternative coordinating groups. Eventually, the opportunities offered by this recent research topic, in terms of both synthesis pathways and modulation of pore size and shape, stability and physical properties, are discussed.

Defect-engineered porphyrinic metal-organic framework nanoparticles for targeted multimodal cancer phototheranostics.

Defect-engineered porphyrinic MOF nanoparticles were fabricated with an in situ one-pot protocol using cypate as the co-ligand and modulator. This multifunctional nanoplatform integrated the photothermal and multimodal imaging properties of cypate with the photodynamic effects of porphyrins, thus achieving targeted multimodal cancer phototheranostics after folic acid modification.

A versatile nanoplatform based on multivariate porphyrinic metal-organic frameworks for catalytic cascade-enhanced photodynamic therapy.

In recent years, the antitumor application of photodynamic therapy (PDT) has gained widespread interest in treating solid tumors. Due to the hypoxic environment in tumors, the major limit of PDT seems to be the source of oxygen. In this work, we attempted to relieve hypoxia and enhance photodynamic therapy, and therefore, designed and assembled a catalytic cascade-enhanced PDT multifunctional nanoplatform. The mentioned platform termed UIO@Ca-Pt is based on porphyrinic metal-organic framework (UIO) combination, which is simultaneously loaded by CaO2 NPs with polydopamine (PDA) and then the Pt raw material to further improve biocompatibility and efficiency. In a tumor microenvironment, CaO2 could react with water to generate calcium hydroxide and hydrogen peroxide, which was further decomposed by Pt nanoparticles to form oxygen, thereby facilitating the generation of cytotoxic singlet oxygen by photosensitizer TCPP under laser irradiation. Both in vitro and in vivo experiment results confirmed the excellent oxygen production capacity and enhanced PDT effect of UIO@Ca-Pt. With guaranteed safety in PDT, the oxygen-supplying strategy might stimulate considerable interest in the development of various metal-organic materials with multifunctionality for tumor diagnosis and therapy.

PCN-222@g-C3N4 cathodic materials for "signal-off" photoelectrochemical sensing of kanamycin sulfate.

A novel cathodic photoelectrochemical (PEC) sensor was developed for the ultrasensitive detection of kanamycin sulfate (KAM) based on the g-C3N4 coupled zirconium-based porphyrinic metal–organic framework (PCN-222). Photocathodes made by double n-type semiconductors, which was attributed to the transfer of electrons and holes from g-C3N4 broad band to PCN-222 with narrow band gap. The photocurrent decreased when KAM was added, which was conducive to the construction of the PEC sensor. Then, the PCN-222@g-C3N4 was used as a photosensitive platform to construct a label-free strategy and ultrasensitive detection of KAM with wide linear range from 1 to 1000 nM and a low detection limit of 0.127 nM. Moreover, this sensing platform shows good selectivity, favourable reproducibility and brilliant stability. The reported sensors provided great potential for the detection of KAM in actual samples.

Morphological and Structural Elucidation of Room Temperature Catalytic Degradation of Amoxicillin Antibiotic Using Zinc Porphyrin Metal Organic Framework

Environment is witnessing an extensive increase in persistent and bioactive micro pollutants from the last few decades. Since most clinical modalities are flooded with antibiotics, environmental samples such as sewage treatment effluents, surface water and secondary water drainage etc. reveal the presence of bio-recalcitrant antibiotics worldwide, ergo there is a spurring rise in antibiotic resistant microorganisms. In order to circumvent the escalating concentration of amoxicillin (microgram/liter) we contrived a potential metal organic framework (MOF) and lab tested it for catalytic functionality. A zinc-porphyrin MOF using Tetra (4-carboxyphenyl) porphyrin H2TCPP (>97%) as a ligand and Zinc acetate as a metal salt was solvo-thermally synthesized. The morphological and structural characterization were performed using FESEM, XRD, EDAX, FTIR and UV-Visible spectroscopy. The fabricated MOF catalyst exhibits sterling ability of amoxicillin degradation in a dark environment at room temperature, accounting a degradation efficiency of about 97.3% in a 0.1 mg/ml concentration. 90 minutes of catalyst exposure to the antibiotic shows maximum degradation after which there is no further change in amoxicillin concentration. First time we have exploited electrochemical cyclic voltametric (CV) measurement to monitor the degradation process which was validated by FTIR recording, and noticed that the degradation process followed a first order kinetics. We have also discussed the morphological stability of the fabricated Zn porphyrin MOF after antibiotic exposure and reported a comparative outline between catalytic efficiency of different MOF species. High porosity and effective charge transfer between carboxyphenyl) porphyrin ligand to vacant d orbital of Zn+2 are pivotal factors for effective sorption and degradation of amoxicillin antibiotics dark at room temperature. We would expect the developed Zn porphyrin MOF is very promising for successful commercial application due to its energy efficiency (dark) and simple process for effective degradation of antibiotics.

A metal-porphyrinic framework film as an efficient optical limiting layer in an electro-optical switchable device.

Herein we report a 2D surface-coordinated porphyrinic metal-organic framework film (SURMOF) CuTCPP prepared by a layer by layer method as an optical limiting layer in a polymer-dispersed liquid crystal (PDLC) device. The results show that the CuTCPP SURMOF/PDLC device has excellent switchable transparency and optical limiting performance, providing a new route to achieve mutilfunctional electro-optical applications.

Enhancing selectivity through decrypting the uncoordinated zirconium sites in MOF electrocatalysts.

Zirconium (Zr)-based porphyrinic metal-organic frameworks (PCN-223-M) were employed as the electrocatalysts to explore the effect of uncoordinated Zr sites on the performance of the CO2 reduction reaction (CO2RR). PCN-223-AA with the lowest uncoordinated number of 0.79 exhibited the highest FE(CO) of 90.7%. It was demonstrated that the catalytic performance of PCN-223-M showed negative correlation to the uncoordinated Zr sites. This research provided a rational strategy to design efficient MOF electrocatalysts with few uncoordinated metal sites for highly selective CO2RR.

Core-shell gold nanorod@mesoporous-MOF heterostructures for combinational phototherapy.

Despite the increasing usage of porphyrinic metal-organic frameworks (MOFs) for combination therapy, the controlled encapsulation of inorganic nanoparticle-based therapeutics into such MOFs with specific structures has remained a major obstacle for improved tumor therapy. Here, we report the synthesis of a mesoporous MOF shell on the surface of gold nanorods (AuNRs), wherein a single AuNR is captured individually in single-crystalline MOFs with a controlled crystallographic orientation, for combinational phototherapy against solid tumors. The core-shell heterostructures have the benefits of a mesoporous structure and photoinduced singlet oxygen generation behavior characterized by the porphyrinic MOF shell, together with the plasmonic photothermal conversion characteristic of AuNRs. We demonstrated that the AuNR@MOF nanoplatform enables an efficient tumor treatment strategy by combining photodynamic therapy and photothermal therapy. We should emphasize that such systems could have applications beyond the field of cancer therapy, like plasmonic harvesting of light energy to induce and accelerate catalytic reactions within MOFs and multifunctional nanocarriers for agricultural formulations.

Ultra-thin metal-organic framework nanosheets for chemo-photodynamic synergistic therapy.

Synergistic therapies, such as chemo-photodynamic therapy, have been growing fast because of their efficacy against cancers. Although metal-organic frameworks have been widely studied in the field of drug delivery, the metal-organic frameworks (MOFs) with a two-dimensional (2D) structure integrated by photosensitizers are rarely reported. However, chemo-photodynamic therapy still has limitations such as the inhibitory effect from intracellular glutathione (GSH). In this work, a simple bottom-up synthesis method was used to synthesize a pH-responsive drug delivery system with a 2D MOF structure. In particular, tetracarboxyporphyrin (TCPP) derivatives were coordinated with bivalent copper ions as organic bridging molecules in a polyvinylpyrrolidone (PVP) solution, and copper porphyrin MOFs (Cu-TCPP nanosheets) were synthesized by a hydrothermal method from bottom to top. DOX was loaded onto Cu-TCPP nanosheets by π-π stacking with a high drug loading rate of 33%. DOX@Cu-TCPP nanosheets showed pH-responsive DOX releasing behaviour and significant GSH scavenging ability. In addition, the evaluation of in vitro and in vivo treatment showed that DOX@Cu-TCPP nanosheets had high anti-tumor activity and excellent biocompatibility. Therefore, this study opens a new idea for the application of MOF nanosheets in tumor therapy and provides a supporting basis for the treatment of cancers by chemo-photodynamic synergistic therapy.

Straightforward synthesis of a porous chromium-based porphyrinic metal-organic framework for visible-light triggered selective aerobic oxidation of benzyl alcohol to benzaldehyde

Among MOFs, chromium-based metal–organic frameworks (Cr-MOFs) represent attractive scaffolds for variety of potential applications due to their high porosity and stability. Nevertheless, Cr-MOFs are not very common due to complicate synthesis. Cr-MOFs of large linkers are one clear example of synthetic limitations, since their preparation takes place by post-synthetic routes, commonly starting from Fe-MOFs as precursors. Hence, in this work, the direct synthesis of a phorphyrinic chromium-based MOF, Cr-PCN-600 (PCN stands for Porous Coordination Network) under solvothermal conditions is reported. The resulting Cr-MOF exhibits high surface area, permanent porosity, and broad light absorption wavelength range. Interestingly, this Cr-MOF is a highly effective heterogeneous photocatalyst for the selective aerobic oxidation of benzyl alcohol to benzaldehyde under visible light irradiation without any additive. Importantly, the Cr-MOF showed good recyclability maintaining its activity for three runs. The present results lay the foundation for both synthesis and applications of Cr-MOFs as robust photocatalysts in advanced organic transformations. Notably, quenching studies confirmed the generation of superoxide radical anion (O2−) and singlet oxygen (1O2) (mostly) as reactive species under the reaction conditions.

A hybrid of ultrathin metal-organic framework sheet and ultrasmall copper nanoparticles for detection of hydrogen peroxide with enhanced activity.

Here, we design and synthesize a novel 2D Cu-tetrakis(4-carboxyphenyl)porphyrin (TCPP) metal-organic framework (MOF) sheet and ultrasmall Cu5.4O nanoparticle (Cu5.4O USNP) hybrid (Cu-TCPP MOF/Cu5.4O nanocomposite). The graphene-like ultrathin Cu-TCPP MOF sheets offer high surface-to-volume atom ratios and many active sites, which is beneficial for loading more Cu5.4O USNPs. The Cu5.4O USNPs with ultrasmall size (<5nm) have promising conductivity and excellent enzymatic ability for H2O2. The successfully prepared nanocomposites are characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) techniques. The 2D graphene-like ultrathin Cu-TCPP MOF sheets show no H2O2-sensing signals, whereas Cu5.4O USNPs exhibit a clear reduction peak for detection of H2O2. Interestingly, the combination of two kinds of nanomaterials improved the H2O2 sensing ability due to their synergistic effect. The properties of the unmodified electrodes and the Cu-TCPP MOF/Cu5.4O nanocomposite-modified electrodes were systemically studied by cyclic voltammetry (CV), current-time (i-t) response, and square-wave voltammetry (SWV) techniques. The electrochemical sensor for the detection of H2O2 based on the Cu-TCPP MOF/Cu5.4O nanocomposite has a lower detection limit of 0.13μmol·L-1 and wider linear range of 0.1 × 10-6 ~ 0.59 × 10-3mol·L-1 and 1.59 × 10-3 ~ 20.59 × 10-3mol·L-1 when compared with the Cu5.4O USNPs-modified electrode. The electrochemical sensor can be further used to detect H2O2 produced by cells. Graphical abstract The mechanism for sensing H2O2 produced from cells based on a Cu-TCPP MOF/Cu5.4O USNPs nanocomposite-modified electrode.

Cover Feature: A Mixed‐Metal Porphyrinic Framework Promoting Gas‐Phase CO2 Photoreduction without Organic Sacrificial Agents (ChemSusChem 23/2020)

The Cover Feature shows how, serving as an artificial photosynthesis system, the rationally designed Ti/Zr porphyrinic metal–organic framework demonstrates gas-phase water oxidation-assisted selective photoreduction of CO2 under visible-light irradiation. More information can be found in the Communication by W.-Y. Gao, H. T. Ngo, et al.

Rugby-ball like Ag modified zirconium porphyrin metal–organic frameworks nanohybrid for antimicrobial activity: Synergistic effect for significantly enhancing photoactivation capacity

Despite of the current advancement in antibacterial material, the bacterial issues are still great challenges in health problems worldwide. Herein, Ag nanoparticles doped to zirconium porphyrin metal–organic frameworks (ZPM@Ag) were synthesized for antibacterial activity. The effect of different dosage of Ag nanoparticles on the antibacterial activity was also investigated. The morphology, porous microstructure, and composition of the prepared nanohybrids were characterized by SEM, TEM, XRD, FT-IR, XPS and BET analysis. The results revealed that the optimized antimicrobial efficiency was ZPM@Ag(2). The reactive oxygen species (ROS) production of ZPM@Ag(2) under visible light was obviously abundant than that in the dark, and moreover, the nanohybrid exhibited high antimicrobial efficacy. Furthermore, the antimicrobial mechanism of the prepared sample was also carefully investigated. The enhanced photoactivation antimicrobial activity could be ascribed to the synergistic effect between zirconium porphyrin MOFs (ZPM) and Ag nanoparticles, which possesses high specific surface area and abundant active sites due to the uniform rugby-ball like shape. ZPM@Ag(2) nanohybrid was demonstrated excellent stability even after five cycles. The antimicrobial Ag nanoparticles immobilized in photocatalytic antibacterial porous MOFs are expected to provide a guideline to broaden the applications of MOFs and design novel metal-based antibacterial nanomaterials.

Porphyrin-Based Metal-Organic Frameworks for Biomedical Applications.

Porphyrins and porphyrin derivatives have been widely explored for various applications owing to their excellent photophysical and electrochemical properties. However, inherent shortcomings, such as instability and self‐quenching under physiological conditions, limit their biomedical applications. In recent years, metal–organic frameworks (MOFs) have received increasing attention. The construction of porphyrin‐based MOFs by introducing porphyrin molecules into MOFs or using porphyrins as organic linkers to form MOFs can combine the unique features of porphyrins and MOFs as well as overcome the limitations of porphyrins. This Review summarizes important synthesis strategies for porphyrin‐based MOFs including porphyrin@MOFs, porphyrinic MOFs, and composite porphyrinic MOFs, and highlights recent achievements and progress in the development of porphyrin‐based MOFs for biomedical applications in tumor therapy and biosensing. Finally, the challenges and prospects presented by this class of emerging materials for biomedical applications are discussed.

Palladium Nanocrystals‐Engineered Metal–Organic Frameworks for Enhanced Tumor Inhibition by Synergistic Hydrogen/Photodynamic Therapy

AbstractHydrogen therapy, as a star therapeutic modality, has recently acquired much attention in the field of anticancer medicine. Evidence suggests that hydrogen can selectively reduce intratumoral overexpressed hydroxyl radicals (•OH) to break the redox homoeostasis and thereby result in redox stress and cell damage. As a reactive oxygen species‐related noninvasive modality, photodynamic therapy (PDT) has been approved for varied tumor treatments clinically. For implementing tumor therapy with enhanced anticancer efficacy and attenuated side effects, here a biocompatible palladium nanocrystals‐integrated nanoscale porphyrinic metal–organic framework (NPMOF) is designed to develop a novel combined therapy modality, that is, synergistic hydrogen/photodynamic therapy. The NPMOF is employed simultaneously as the photosensitizer for PDT and as the nanocarrier to support palladium nanocrystals, which is further used as the hydrogen vehicle. The final hydrogen‐containing nanosystems exhibit a persistent reductive hydrogen release behavior and considerable light‐activated singlet oxygen (1O2) generation without mutual interference, contributing to the adequate disturbance of tumor microenvironment redox steady‐state for synergistically inducing tumor cell death. Ultimately, by coupling of tumor‐selective hydrogen therapy and PDT, the designed nanosystems realize the augmented therapeutic outcome with minimal side effects, providing a safe and efficient tumor treatment for future clinical translation.

Tumor targeted self-synergistic nanoplatforms for arsenic-sensitized photodynamic therapy

Development of antitumor agents with high efficiency and low toxicity is one of the most important goals for biomedical research. However, most traditional therapeutic strategies were limited due to their non-specificity and abnormal tumor microenvironments, causing a poor therapeutic efficiency and severe side effects. In this paper, a tumor targeted self-synergistic nanoplatform (designated as PAO@PCN@HA) was developed for chemotherapy sensitized photodynamic therapy (PDT) against hypoxic tumors. The efficient drug loading of phenylarsine oxide (PAO) in porphyrinic metal organic framework of PCN-224 as well as the surface modification of hyaluronic acid (HA) improved the targeted drug delivery and reduced the side effects of PAO at the therapeutic dose. Particularly, PAO as an arsenical-based chemotherapeutic agent could not only induce cell apoptosis by generating reactive oxygen species (ROS), but also regulate tumor microenvironments to improve the PDT effect of PCN-224 by mitigating hypoxia and consuming cellular GSH. Both in vitro and in vivo investigations confirmed an effective self-synergy of PAO@PCN@HA in hypoxic tumor therapy with a low systemic toxicity. This integration of microenvironment adjustment with tumor targeted self-synergistic mechanism might provide a new insight for the development of arsenic-based antitumor strategy for clinical applications.