Metal Porphyrins Research Articles

Efficient and selective oxidation of 5-hydroxymethylfurfural catalyzed by metal porphyrin supported by alkaline lignin: Solvent optimization and catalyst loading

Cobalt (II)-meso-tetra(4-carboxyphenyl) porphyrin supported by deprotected lignin was synthesized through the covalent linkage between carboxy groups in the porphyrin and hydroxyl groups in the lignin. The resulting supporting catalysts were applied in the selective oxidation of 5-hydroxymethylfurfural. Through solvent optimization, 5-hydroxymethyl-2-furancarboxylic acid and 2,5-furandicarboxylic acid could be selectively obtained. Steric effect of lignin prevented unwanted aggregation-caused quenching, avoiding catalyst deactivation. Thus, supported catalysts displayed better catalytic efficiency compared free metal porphyrin catalyst. Unlike the excessive use of sodium hydroxide in the oxidation of HMF catalyzed by metal catalysts, an equivalent amount of sodium hydroxide was used in this oxidation process. Meanwhile, lower activation energy was detected when metal porphyrin supported by deprotected lignin was used. By adjusting the pH in the reaction, supported catalysts could be reused. The catalytic activity remained stable during the recycling experiments.

Enhanced degradation of bisphenol F in a porphyrin-MOF based visible-light system under high salinity conditions

The efficient degradation of organic contaminants in practical water treatment is a challenge for advanced oxidation processes via such as semiconductor photocatalysis due to interference from the inhibiting influence due to the reactions between radicals and coexisting anions in the actual water column. Herein, a porphyrinic zirconium metal–organic framework (PCN-223) is used in a visible light system to effectively decompose bisphenol F (BPF) in saline water. The PCN-223/visible-light system can effectively resist the influence of environmental coexisting anions and natural organic matter (NOM), thus demonstrating excellent performance in decomposing pollutants. Furthermore, the catalytic system is able to maintain stable contaminant degradation over a wide pH range and in five water matrices. Coexisting anions promote the conductivity of electrons by forming ionic bonds with Zr, which enhances light-induced electron transfer under visible light. This work illustrates the mechanism and conditions under which porphyrin-MOF can resist high salt environments in photocatalysis, and provides a new perspective on the practical application of photocatalysis to overcome complex environmental disturbances.

Cu (II)-porphyrin metal-organic framework/graphene oxide: synthesis, characterization, and application as a pH-responsive drug carrier for breast cancer treatment.

A new multifunctional graphene oxide/Cu (II)-porphyrin MOF nanocomposite (CuG) comprised of Cu-TCPP MOF supported on graphene oxide (GO) nanosheets, has been fabricated by a solvothermal method at low temperature and one-pot process. Cu-TCPP MOF with universal advantages, such as high porosity, nontoxicity, large surface area, and safe biodegradation, combined with GO allows the achievement of an efficient doxorubicin loading (45.7%) and smart pH-responsive release for chemotherapy. More significantly, more than 97% of DOX was released by CuG at pH 5 which was more than that at pH 7.4 (~ 33.5%), while Cu-TCPP MOF displayed DOX release of 68.5% and 49% at pH 5 and 7.4, respectively, illustrating the effect of GO on the smart MOF construction for controllable releasing behavior in vitro. The results of in vitro anticancer experiments demonstrate that the developed nanocarrier exhibited slight or no cytotoxicity on normal cells, while the drug-loaded nanocarrier increased significant cancer cell-killing ability with higher therapeutic efficacy than free DOX, indicating the sustained release behavior of the CuG nanocarrier without any "burst effect". Moreover, the in vivo experiments demonstrated that the CuG-DOX exhibited significantly higher anticancer efficiency compared with free DOX. High anti-cancer therapeutic efficacy of this nanoscale carrier as an efficient pH sensitive agent, has the potential to enter further biomedical investigations. A new smart multifunctional graphene oxide-Cu (II)-porphyrin MOF nanocomposite (CuG) formed of Cu-TCPP MOF and graphene oxide (GO) has successfully fabricated and demonstrated an efficient pH-responsive drug release behavior in cancer therapy without using any targeting ligand.

Adsorptive Removal of Industrial Dye by Nanoporous Zr porphyrinic Metal–Organic Framework Microcubes

Increasing anthropogenic activities have adversely affected freshwater supply, making it an important global issue. Water resources are often contaminated by industrial dyes, which may harm both en...

Temperature-responsive polymer-tethered Zr-porphyrin MOFs encapsulated carbon dot nanohybrids with boosted visible-light photodegradation for organic contaminants in water

Zirconium-based porphyrin metal–organic frameworks (MOFs) have attracted extensive attention in the photocatalysis because of their considerable specific surface area, powerful visible light efficiency and semiconductor properties. However, the rapid charge recombination and self-aggregation limit their applications. Here, porphyrin-based Zr-MOF (PCN-222) nanohybrids (CDs@PCN-222@PNIPAM) as an efficient hydrophilic photocatalyst were fabricated by encapsulating various carbon dots (CDs) into PCN-222 nanopores with surface wettability modification by catechol-terminated thermo-responsive PNIPAM having various chain lengths. Due to the electron collecting effect of the nitrogen-doped CDs (N-CDs) and their synergistic effect with PCN-222, the photocatalytic performance of the prepared nano-hybrid photocatalyst were significantly improved. Furthermore, the introduction of hydrophilic polymer with moderate molecular weight effectively enhanced the transfer efficiency of photo-generated charges and the surface wettability of photocatalyst, and improved the water dispersibility of catalyst so that effectively promotes the enrichment and catalytic conversion of water-soluble target pollutants around the active site of the photocatalyst. The removal efficiency of RhB and tetracycline (TC) under visible light irradiation reached almost 100 % and 90.93 % in just 20 min, respectively. In addition, polymer-functionalized Zr-MOF-based nanohybrids revealed an interesting temperature-response switching behavior for the photocatalysis. The study on the catalytic mechanism and degradation pathways of TC showed that the h+ plays a major role in the degradation process, and other reactive species are also involved in the further mineralization of pollutants. This work provides a new insight for the functional modification of MOFs and the design of high efficiency photocatalyst.

Enhanced quantum capacitance in 3d-transition metal porphyrin functionalized graphene

Application of the functionalized graphene as electrode for supercapacitor has received a lot of attention recently. In the present work, we investigate applicability of transition metal atom decorated defective graphene for enhanced quantum capacitance compared to pristine graphene. The calculated results based on density functional theory find that Mn, Fe, Co, and Ni prefer in-plane configurations, and Sc, Ti, V, and Cr prefer an out-of-plane configuration of the functionalized graphene. A significant increase in quantum capacitance for the porphyrin functionalized graphene is predicted with the peak value is 149μF/cm2. Decoration of transition metal atoms results into lowering of quantum capacitance except for Sc and Fe for which we predict the capacitance to be 177μF/cm2 and 220μF/cm2, respectively. The results clearly show that degree of localization of 3d states near the Fermi level essentially controls the value of the quantum capacitance in metal decorated functionalized graphene.

Ligand-Directed Conformational Control over Porphyrinic Zirconium Metal-Organic Frameworks for Size-Selective Catalysis.

Zirconium-based metal-organic frameworks (Zr-MOFs) have aroused enormous interest owing to their superior stability, flexible structures, and intriguing functions. Precise control over their crystalline structures, including topological structures, porosity, composition, and conformation, constitutes an important challenge to realize the tailor-made functionalization. In this work, we developed a new Zr-MOF (PCN-625) with a csq topological net, which is similar to that of the well-known PCN-222 and NU-1000. However, the significant difference lies in the conformation of porphyrin rings, which are vertical to the pore surfaces rather than in parallel. The resulting PCN-625 exhibits two types of one-dimensional channels with concrete diameters of 2.03 and 0.43 nm. Furthermore, the vertical porphyrins together with shrunken pore sizes could limit the accessibility of substrates to active centers in the framework. On the basis of the structural characteristics, PCN-625(Fe) can be utilized as an efficient heterogeneous catalyst for the size-selective [4 + 2] hetero-Diels-Alder cycloaddition reaction. Due to its high chemical stability, this catalyst can be repeatedly used over six times. This work demonstrates that Zr-MOFs can serve as tailor-made scaffolds with enhanced flexibility for target-oriented functions.

Driving Organic Nanocrystals Dissolution Through Electrochemistry.

We have recently discussed how organic nanocrystal dissolution appears in different morphologies and the role of the solution pH in the crystal detriment process. We also highlighted the role of the local molecular chemistry in porphyrin nanocrystals having comparable structures: in water‐based acid solutions, protonation of free‐base porphyrin molecules is the driving force for crystal dissolution, whereas metal (ZnII) porphyrin nanocrystals remain unperturbed. However, all porphyrin types, having an electron rich π‐structure, can be electrochemically oxidized. In this scenario, a key question is: does electrochemistry represent a viable strategy to drive the dissolution of both free‐base and metal porphyrin nanocrystals?In this work, by exploiting electrochemical atomic force microscopy (EC‐AFM), we monitor in situ and in real time the dissolution of both free‐base and metal porphyrin nanocrystals, as soon as molecules reach the oxidation potential, showing different regimes according to the applied EC potential.

A MnO2-coated multivariate porphyrinic metal–organic framework for oxygen self-sufficient chemo-photodynamic synergistic therapy

Lately, chemotherapy and photodynamic therapy (PDT) synergistic therapy has become a promising anti-cancer treatment mean. However, the hypoxia in tumor leads to huge impediments to the oxygen-dependent PDT effects. In this work, a multifunctional nanoplatform (TUDMP) based on a multivariable porphyrin-nMOFs core and a manganese dioxide (MnO2) shell was prepared for relieving tumor hypoxia and enhancing chemo-photodynamic synergistic therapy performance. The obtained TUDMP nanoplatform could effectively catalyze the hydrolysis of hydrogen peroxide to generate oxygen and also lead to consumption of antioxidant GSH, thereby facilitating the production of cytotoxic reactive oxygen species (ROS) by photosensitizer under laser irradiation. More importantly, the decomposition of the MnO2 shell would further promote the release of the loaded doxorubicin (DOX), and thus an efficient chemo-PDT synergistic therapy was realized. Both in vitro and in vivo experimental results demonstrated the oxygen self-sufficient multifunctional nanoplatform could exhibit significantly enhanced anticancer efficiencies compared with chemotherapy or PDT alone.

Electrospun pullulan/PVA nanofibers integrated with thymol-loaded porphyrin metal−organic framework for antibacterial food packaging

Pathogenic microorganisms posed perniciousness for postharvest fruits and vegetables, as well as brought potential risks for human health. In this work, pullulan/polyvinyl alcohol (PUL/PVA) nanofibers incorporated with thymol-loaded porphyrin metal-organic framework nanoparticles (THY@PCN-224 NPs) were developed for antibacterial food packaging. PCN-224 MOFs not only act as thymol loading carriers but also highly produce singlet oxygen (1O2) with bactericidal activity. PUL/PVA nanofiber was a promising sustainable substrate because of its good flexibility, biocompatibility and biodegradability. The loading capacity of PCN-224 for thymol was about 20%. The THY@PCN/PUL/PVA nanofibers exhibited synergistic antibacterial activities against E. coli (~99%) and S. aureus (~98%) under light irradiation. The cell viability assays and fruit preservation study demonstrated good biosafety of the polymeric film. The results suggested that this novel nanofiber has potential application prospects for food packaging.

Mechanistic Investigations into and Control of Anisotropic Metal–Organic Framework Growth

The porphyrinic metal-organic framework, PCN-222, exhibits anisotropic growth behavior to form nanorods and microrods with aspect ratios 3 < x < 94. Control of microrod aspect ratios has been demonstrated through the identification of several factors that dictate crystal growth, particularly the concentrations of a ligand, a modulator, and an exogenous base. An increase in the local concentration of a deprotonated ligand, which is proportional to the nucleation rate, is associated with smaller crystals, while increased modulator concentration leads to longer microrods. Addition of a deprotonating agent not only contributes to higher aspect ratios but also results in an improvement to particle dispersity. Here, we report acid-base co-modulation methods with difluoroacetic acid and triethylamine to effectively tune PCN-222 aspect ratios. A series of mechanisms is identified for the growth of PCN-222: (1) ligand deprotonation, (2) nucleation, (3) oriented attachment, (4) Ostwald ripening, and (5) dissolution-recrystallization. Time trials of co-modulated samples revealed three separate ripening growth events, with each resulting in larger and more monodisperse crystals. With an understanding of these crystal growth factors and mechanisms, the highest aspect ratio, non-templated metal-organic frameworks were synthesized (94 ± 9).

Synthesis of Porphyrin Zr-MOFs for the Adsorption and Photodegradation of Antibiotics under Visible Light.

The release of antibiotics into the water environment can pose a serious threat to human and ecological health, so it is of great significance to effectively remove antibiotics from wastewater. In this work, porphyrinic zirconium metal–organic framework material, PCN-224, was first explored for the adsorption removal of antibiotics from water using tetracycline (TC) and ciprofloxacin (CIP) as examples. We prepared a series of PCN-224 with different particle sizes (150 nm, 300 nm, 500 nm, and 6 μm). Benefiting from the huge surface area (1616 m2 g–1), the 300 nm-PCN-224 sample had the best adsorption properties for TC and CIP. Remarkably, it exhibits fast removal rates and high adsorption capacities of 354.81 and 207.16 mg g–1 for TC and CIP, respectively. The adsorption of TC and CIP in 300 nm-PCN-224 is consistent with the pseudo-second-order kinetic model and Langmuir isotherm model, which indicates that the adsorption can be regarded as homogeneous monolayer chemisorption, and the adsorption is exothermic, which has been confirmed by thermodynamic studies. Under visible-light irradiation, 300 nm-PCN-224 exhibited high photocatalytic activity for TC and CIP. The adsorption studies confirmed that the adsorption of adsorbates takes place via the formation of hydrogen bonding, π–π interactions, and electrostatic attraction. In addition, the adsorbent can be simply regenerated by photocatalysis under visible light, and the adsorption–desorption efficiency is still above 85% after repeated use five times. The work of MOFs to remove antibiotics from water shows that MOFs have great potential in this field and are worthy of further study.

Upconverted Metal-Organic Framework Janus Architecture for Near-Infrared and Ultrasound Co-Enhanced High Performance Tumor Therapy.

Strict conditions such as hypoxia, overexpression of glutathione (GSH), and high concentration of hydrogen peroxide (H2O2) in the tumor microenvironment (TME) limit the therapeutic effects of reactive oxygen species (ROS) for photodynamic therapy (PDT), chemodynamic therapy (CDT), and sonodynamic therapy (SDT). Here we fabricated a biocatalytic Janus nanocomposite (denoted as UPFB) for ultrasound (US) driven SDT and 808 nm near-infrared (NIR) light mediated PDT by combining core-shell-shell upconversion nanoparticles (UCNPs, NaYF4:20%Yb,1%Tm@NaYF4:10%Yb@NaNdF4) and a ferric zirconium porphyrin metal organic framework [PCN-224(Fe)]. Our design not only substantially overcomes the inefficient PDT effect arising from the inadequate Förster resonance energy transfer (FRET) process from UCNPs (donor) to MOFs (acceptor) with only NIR laser irradiation, but also promotes the ROS generation via GSH depletion and oxygen supply contributed by Fe3+ ions coordinated in UPFB as a catalase-like nanozyme. Additionally, the converted Fe2+ from the foregoing process can achieve CDT performance under acidic conditions, such as lysosomes. Meanwhile, UPFB linked with biotin exhibits a good targeting ability to rapidly accumulate in the tumor region, verified by fluorescence imaging and T2-weighted magnetic resonance imaging (MRI). In a word, it is believed that the synthesis and antitumor detection of UPFB heterostructures render them suitable for application in cancer therapeutics.

CO2 electrochemical reduction to methane on transition metal porphyrin nitrogen-doped carbon material M@d-NC: theoretical insight

CO2 electrochemical reduction to methane on transition metal porphyrin nitrogen-doped carbon material M@d-NC: theoretical insight

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.

Robust photocatalytic hydrogen production on metal-organic layers of Al-TCPP with ultrahigh turnover numbers

The development of robust photocatalytic systems is key to harvest the solar power for hydrogen production. In the current study, a series of aluminum-based porphyrinic metal organic frameworks (Al-TCPP) with various morphologies of bulk, carambola-like and nanosheets are synthesized with modulated layer thickness. Morphology-dependent photocatalytic activities in hydrogen production are witnessed and inversely correlate to the thickness of the Al-TCPP micro-platelets or nanosheets. Particularly, the exfoliated metal organic layers (MOLs) of Al-TCPP demonstrated a high hydrogen yield rate of 1.32 × 104 µmol h−1 g−1 that is 21-fold of that from the bulk catalyst, as well as an exceptional TON of 6704 that seldom seen in literature. Through comprehensive photochemical characterizations, the remarkable photocatalytic performance of Al-TCPP-MOL is attributed to the great charge separation efficiency and transfer kinetics endowed by the ultrathin 2D morphology with extended active surface area.

Bioinspired N4-metallomacrocycles for electrocatalytic oxygen reduction reaction

• Summarizing the ORR features of bioinspired N 4 -metallomacrocycles. • Discussing the structural effects of N 4 -metallomacrocycles on ORR. • Summarizing immobilization methods for loading N 4 -metallomacrocycles on various supports. • Summarizing electrocatalytic ORR materials derived from N 4 -metallomacrocycles. • Discussing potential applications of N 4 -metallomacrocycles in new energy conversion techniques. Oxygen reduction reaction (ORR) is an important process involved in natural and artificial energy conversion schemes. As inspired by cytochrome c oxidases (C c Os), which are metalloenzymes catalyzing selective reduction of O 2 to water at heme Fe porphyrin sites, metal macrocyclic complexes containing square-planar M−N 4 coordination sites, such as metal porphyrins, corroles and phthalocyanines, have been extensively studied as catalysts and pre-catalysts for electrocatalytic ORR. This review addresses structural effects of these molecular metal macrocycles on the selectivity and activity of electrocatalytic ORR, including the effects of meso - and β -substituents, axial ligands, and second coordination spheres. In order to realize the practical use of molecular electrocatalysis, catalysts are required to be immobilized on appropriate supporting materials. Therefore, this review also addresses the effects of immobilization methods and interactions between molecular catalysts and supports on ORR. Moreover, the use of N 4 -metallomacrocycles and their derived materials in metal-air batteries is discussed, underlining the potential and promising applications of molecular electrocatalysis in new energy conversion techniques.

The Origin, Physicochemical Properties, and Removal Technology of Metallic Porphyrins from Crude Oils

Crude oil is an indispensable energy feedstock for daily activities, although some amounts of metallic porphyrins components with undesired characteristics have been identified. These constituents are assumed to originate from the geochemical process of chlorophyll and heme derivatives. In addition, their chemical structures have been thoroughly characterized using spectroscopy techniques, while several analytical methods were adopted in the detection and concentration quantification in the crude oils. The metallic porphyrins have several demerits, including the deactivation of used catalysts, contamination of the treated petrochemical products, and corrosion of the industrial equipment. Also, the removal process is considered challenging due to the strong interaction with the asphaltene fraction of crude oil. This review article, therefore, provides brief information on the origin, physicochemical properties, and possible removal technology of metallic porphyrins from crude oil samples. Besides, a better understanding of chemistry contributes a useful insight towards the development and establishment of better futuristic processing technology.

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.

First-principles study of hybrid nanostructures formed by deposited phthalocyanine/porphyrin metal complexes on phosphorene

Porphyrin and phthalocyanine metal complexes are organic semiconductor molecules, also known as MN4 macrocyclic compounds, widely implemented as photosensitizers and electrocatalysts in solution. In this regard, phosphorene, an emerging layered material entirely composed of phosphorous atoms, shows excellent potential features to act as a building block of novel hybrid nanostructures with organic molecules. Here, we perform a first-principles study of hybrid nanostructures formed by phosphorene nanosheets and deposition of MN4 compounds (where M: Fe, Co, Ni, Zn). It is found that the MN4-phosphorene hybrids have remarkable stability in the gas phase and aqueous solution, comparable to that achieved with carbonaceous and metallic-based substrates. In terms of structure, the hybrid structures display non-degenerated adsorption patterns at room temperature, denoting the formation of stable ordered flat MN4 layers (self-assembly). To understand the origin of the binding stability, we conducted further analysis of binding and energy decomposition (ALMO-EDA). It is revealed that the stability is driven by the interplay between permanent electrostatic and dispersion physical effects, which stand for up to 90% of the stabilizing interaction energy. In terms of electronic properties, on the one hand, spin-polarized complexes do not show either switching in their spin state or substrate magnetization. On the other hand, all MN4 complexes act as mild n-dopants, slightly decreasing the phosphorene bandgap but retaining the topology of frontier orbitals concerning the free complexes for orbital-controlled reactions, e.g., electrochemical reactions in solution. In terms of optical properties, phosphorene induces shifting in the Q-band of phthalocyanines to longer wavelengths, which turns (metal)phthalocyanine-phosphorene hybrid materials into excellent candidates for the design of light-harvesting devices.