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Constructing molecule@support composites is an attractive strategy to realize heterogeneous molecular electrocatalysis. Herein, we synthesized metal-organic framework (MOF)-supported molecular catalysts for hydrogen evolution and oxygen reduction reaction (HER/ORR). Ligand exchange strategy was used to prepare molecule@support hybrids due to the same functional group. A series of hybrids were obtained using Co porphyrin (1) and different MOFs including MIL-88(Fe), MOF-5(NiCo) and UIO-66(Zr). The 1@MOF-5(NiCo) had the best HER and ORR activity compared with 1@MIL-88(Fe) and 1@MOF-5(NiCo). These hybrids also exhibited tunable selectivity for ORR with four-electron process, which can be attributed to the synergistic effect of porphyrin molecules and MOFs. This work provides a possibility for molecular catalysts to improve activity of HER and tune selectivity of ORR.

Several 2D nanosheets of porphyrin MOFs with various transition-metal clusters as metal nodes were prepared via a simple solvothermal method to apply in the photocatalytic hydrogen evolution, in which the hydrogen production rate of the optimal NS-Cu was as high as 15.39 mmol•g−1•h−1. A series of experimental technologies especially cyclic voltammetry (CV) and Mott-Schottky (M-S) had been adopted to investigate the charge-transfer property of photo-generated electron-hole pairs, it was found that the uniformly dispersed Cu-clusters nodes in the original 2D MOFs played a key role in the electron transfer process, that was, the photo-generated electron transferred from excited state eosin-Y to the Cu-clusters nodes for the efficient hydrogen evolution. The excellent photocatalytic performance could be attributed to the reversible oxidation-reduction process of CuII/CuI, which had excellent electron-receiving and electron-outputting capabilities. Our results provided a novel avenue to adapt the uniformly dispersed metal nodes in the original MOFs as cost-effective noble-metal-free cocatalysts with very high atom-utilization efficiency to improve the photocatalytic hydrogen evolution performance in dye-sensitized system.

Morphology-controlled electrocatalysts with the ability of CO2 adsorption/activation, mass transfer, high stability and porosity are much desired in electrochemical CO2 reduction reaction (CO2RR). Here, three kinds of multi-dimensional nanostructures (i.e., hollow sphere, nanosheets and nanofibers) have been successfully produced through the modulation of porphyrin-based covalent organic frameworks (COFs) with various modulators. The obtained nanostructures with high-stability, large surface-area, and single metal sites enable efficient CO2RR into CH4. Notably, they all exhibit higher FECH4 (hollow sphere, 68.2%; nanosheet, 64.2% and nanofiber, 71.0%, -0.9 V) than COF-366-Cu (43.0%, -0.9 V) after morphology control. Noteworthy, the FECH4 of COF-366-Cu (HS) keeps higher than 52.4% over a wide potential range from -0.9 V to -1.1 V and the achieved FECH4+C2H4 (82.8%, -0.9 V) is superior to most of reported COFs and copper-based electrocatalysts. This work paves a new way in the exploration of COF-based multi-dimensional nanostructures applicable in efficient CO2RR to CH4.

Conjugated molecular thin films have potential for novel optoelectronic devices such as flexible solar cells and display devices. However, a detailed understanding of their excited state dynamics is crucial for their technological applications. Tetrapyrrole complexes are an important class of conjugated organic molecules for optoelectronic applications due to their high light gathering ability and thermal stability. In this review, we summarize excited state dynamics of porphyrin and phthalocyanine molecular thin films investigated by pump–probe techniques. The relaxation dynamics for metallo-phthalocyanine molecules are observed to be ultrafast in nature and are in femtosecond time scale while that for metal free phthalocyanine are moderately fast. In case of metallo-phthalocyanines exciton lifetime is much longer than for metal free phthalocyanines. The central metal atom plays an important role in the excited state dynamics of porphyrin molecular thin films thus providing additional excitation channels. Time-resolved photoemission spectroscopy reveals about the evolution of charge transfer excitons at donor–acceptor interfaces and their dissociation mechanism. In case of metallo-phthalocyanines the exciton transport is dominated by hopping mechanism rather than spatial coherent length of excitons. The pump–probe studies provide a basis for appropriate selection of molecules for technological applications.

In this work, a covalent organic framework (COF), which is constructed by the building blocks of [5,10,15,20-tetrakis(4-aminophenyl)porphinato]copper(II) (CuTAPP) and p-benzaldehyde, is employed to integrate with TiO2 for the purpose of establishing a Z-scheme hybrid. Within the system, isonicotinic acid performs the role of a bridge that connects the two components through a coordination bond. Further photocatalytic application reveals the hybrid framework is able to catalyze CO2 conversion under simulated solar light, resulting in CO production rate of 50.5 μmol g−1 h−1, about 9.9 and 24.5 times that of COF and pristine TiO2, respectively. The ameliorated catalytic performance owes much to the porphyrin block acting as photosensitizer that augments the light absorbance, and the establishment of Z-scheme system between the inorganic and organic components that enhances the separation of the carriers. In addition, the chemical bridge also ensures a steady usage and stable charge delivery in the catalysis. Our study sheds light on the development of versatile approaches to covalently incorporate COFs with inorganic semiconductors.

In recent years, porphyrins with a similar structure to chlorophyll are often used as photosensitizers or reaction centers to improve the light absorption capacity or catalytic selectivity of existing photocatalytic systems. However, photocatalytic reactions include photoelectric conversion, photocarrier transport, and surface reaction, which requires the overall design of porphyrin-based photocatalysts. In this paper, the research work of porphyrin molecular design in heterogeneous photocatalysis in recent years is reviewed. Besides, the application of interface control and spatial confinement effect in porphyrin-based hybrid photocatalyst is introduced. Finally, the future development direction of porphyrin-based photocatalysts is prospected and the main challenges in the research of porphyrin-based photocatalysts is given.

Developing durable photocatalysts with highly efficient antibiotics degradation is crucial for environment purification. Herein, tetra (4-carboxyphenyl) porphyrin (TCPP) was loaded onto the surface of Bi2MoO6 microspheres to gain hierarchical organic–inorganic TCPP/Bi2MoO6 (TCPP/BMO) heterojunctions via a facile impregnation strategy. The catalytic properties of these catalysts were comprehensively investigated through the photodegradation of tetracycline hydrochloride (TC) under visible light. Among all the TCPP/BMO heterojunctions, the highest photodegradation rate constant (0.0278 min−1) was achieved with 0.25 wt% TCPP (TCPP/BMO-2), which was approximately 1.15 folds greater than that of pristine Bi2MoO6 and far superior to pure TCPP. The extremely high photocatalytic performance is attributed to the interfacial interaction between TCPP and Bi2MoO6, which favors the efficient separation of charge carriers and the enhancement of visible-light absorbance. TCPP/BMO-2 possesses high mineralization capability and good recycling performance. Photo-induced O2–, h+, and OH were mainly responsible for the degradation of TC. The degradation pathways of TC and toxicity of degradation intermediates were analyzed based on the intermediates detected by the high performance liquid chromatography-mass spectrometer (HPLC–MS) and the toxicity assessment by the quantitative structure–activity relationship (QSAR) prediction. A possible photocatalytic mechanism over TCPP/BMO is proposed. This work offers an insight in developing the porphyrin-based organic–inorganic heterojunctions for effectively remedying pharmaceutical wastewater.

Chemical scavenging of singlet oxygen by iodobenzenein the presence of (triethyleneglycol)monomethyl ether led to the formation of almost spherical nano-structured iodosylbenzene in water, water/acetonitrile and acetonitrile. To our knowledge, it is the first report on the direct aerobic photooxidative synthesis of iodosylbenzene.A polymer supported cationic porphyrin, nanoAmbSO3@H2TMPyP, was used as the photosensitizer. The nanoparticles, were characterized by various spectrophotometric and microscopic methods. The reactivity of the secondary oxidant for the oxidation of organic substrates was studied in the oxidation of methyl phenyl sulfide catalyzed by manganese meso-tetrakis(2-methylphenyl)porphyrin.The synthesis of the reactive secondary oxidant, PhIO, is suggestedas an applicable strategy to overcome the problem of very short lifetime of singlet oxygen in organic solvents and water, which decreases the efficiency of singlet oxygen due to the involvement of the oxidant in unwanted physical and chemical quenching pathways.It is noteworthy that due to very short lifetime of singlet oxygen, most of the singlet oxygen produced in the presence of different photosensitizers is deactivated by other species to return to its triplet ground state by physical or non-productive chemical quenching.

Developing large-scale electrocatalysts using molecular complexes for the oxygen evolution reaction (OER) is of great importance. Herein, four cobalt porphyrins and corroles are deposited on electrode substrates using a simple and fast electropolymerization method. Our results showed that Co-1-P@CC, formed by electropolymerizing Co tetrakis(p-N-pyrrolylphenyl)porphyrin (Co-1-P) on carbon cloth (CC), is the most active OER catalyst in the examined Co porphyrins and corroles in alkaline aqueous solutions by displaying an onset overpotential of 380 mV. Long-term electrolysis tests confirmed the stability of these electropolymerized films by functioning as OER electrocatalysts.

Coronavirus disease 2019 is a serious disease that causes acute respiratory syndrome and negatively affects the central nervous system. SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) crosses the blood-brain barrier due to the S protein on the surface of the viral particles. Thus, it is important to develop compounds that not only have an inhibitory effect but are also capable of completely deactivating the S-protein function. This study describes the purposeful modification of porphyrins and proposes compounds, asymmetrically hetaryl-substituted porphyrins with benzothiazole, benzoxazole, and N-methylbenzimidazole residues, to deactivate the S-protein functions. Molecular docking of SARS-CoV-2 proteins with hetaryl-substituted porphyrins showed that the viral proteins S-, N-, and nsp13 exhibited the highest binding affinity. Hetaryl-substituted porphyrins form strong complexes (13–14 kcal/mol) with the receptor-binding domain of the S protein, while the distance from the porphyrins to the receptor-binding motif (RBM) does not exceed 20 Å; therefore, RBM can be oxidized by 1O2, which is generated by porphyrin. Hetaryl-substituted porphyrins interact with the nucleocapsid protein in the serine/arginine-rich region, and a number of vulnerable amino acid residues are located in the photooxidation zone. This damage complicates the packaging of viral RNA into new virions. High-energy binding of hetaryl-substituted porphyrins with the N- and C-terminal domains of nsp13 was observed. This binding blocks the action of nsp13 as an enzyme of exoribonuclease and methyltransferase, thereby preventing RNA replication and processing. A procedure for the synthesis of hetaryl-substituted porphyrins was developed, new compounds were obtained, their structures were identified, and their photocatalytic properties were studied., Graphical abstract Image 1

Polymeric carbon nitride materials show intriguing prospects in numerous light-to-energy conversion applications, but seldom studies focus on their triplet energy transfer, leading to the insufficient lifetime for the photochemical process. Inspired by the porphyrin molecular photocatalyst, single-atom sites (Fe-N4) as triplet sensitizing sites were fabricated in g-C3N4 for the preparation of Fe-g-C3N4, which processes a long-lived triplet emissive state (τPH = 4.93 μs). But under realistic condition for the large-scale production of catalyst, single atoms are inevitable to sinter, resulting in the formation of other metal species. Therefore, the photooxidation of 1,5-dihydroxynaphthalene (1,5-DHN) and the photocatalytic E-Z Isomerization of stilbene were selected as the model reactions to evaluate the influence of various Fe species on the triplet energy transfer. It was found that Fe-N4 sites promote the triplet energy transfer process, while Fe nanoclusters (Fe0) promote the electron transfer and inhibit triplet energy transfer. This finding provides guidance for the rational design of photocatalysts to efficiently improve triplet energy transfer process and its application.

Porphyrin is an important photosensitizer for singlet oxygen (1O2) formation. However, porphyrin derivatives still display low efficiency and difficult recovery. In this work, an Ag-based MOFs (AgTPyP; TPyP, 5,10,15,20-tetra(4-pyridyl) porphyrin) is synthesized. Compared with ligand TPyP, AgTPyP shows nearly 100% conversion and selectivity in the photocatalytic selective oxidation of sulfides to sulfoxides and obvious photodynamic therapeutic effect under visible light. Combined characterizations suggest that 1O2 is the only active oxygen species, which is due to the large exciton binding energy and narrow energy gap between the lowest excited singlet state (S1) and the lowest triplet state (T1) induced by the presence of Ag+ ion. The selectivity and conversion efficiency of five-cycle experiments do not decrease, indicating the excellent stability of AgTPyP. This work provides an alternative approach to simultaneously enhance the exciton effect of porphyrin and stabilize Ag-based photocatalysts.

Organic molecules are promising electrode materials for green and sustainable rechargeable electrochemical energy storage due to their tunable theoretical capacity and environmental friendliness. However, the commercialization of organic electrode materials is impeded by high solubility in electrolytes and inherently low electronic conductivity. Herein, a series of bipolar organic molecules, [5,10,15,20-tetra(ethynyl)porphinato] M(II) (MTEPP, M= Cu, Zn, Mg, 2H), is proposed as new cathode for highly stable dual ion charge storage. The stacking property of the porphyrin molecules is significantly influenced by complex ions and the mixed valence state of cation (Cu+ and Cu2+) renders better charge storage performance in functionalized porphyrin cathode. Reversible capacity of 219 mAh g−1 is obtained for CuTEPP cathode based on a four-electrons transfer and it can be stably cycled up to 1000 times in lithium based organic batteries. Ex-situ spectroscopies as well as simulation studies evidence the multiple electron transfer and the charge storage sites. Highly reversible capability (> 160 mAh g−1) and stable cyclability (> 300 cycles) is also achieved as cathode in both sodium and potassium based organic cells. This study offers a new approach for developing ultrastable and universal organic cathode for electrochemical energy storage.

Zirconium-based porphyrinic MOFs (PMOFs, MOF = metal-organic framework) have gained considerable attention in the field of electric/thermo/photo-catalysis as heterogeneous single-site catalysts; however, the study on multisite synergistic catalysis of PMOFs are rare. Herein, we have successfully developed a highly regio- and stereo-selective synthetic method of (E)-β-vinylboronates through hydroboration of alkynes using PCN-222 (Cu, PCN = porous coordination network) as multifunctional heterogeneous catalyst. Compared with homogeneous catalytic system, high TOF value is achieved in the developed method, originating from the synergistic effect of central Cu(II) ions, N atoms of porphyrin rings and terminal –OH groups on Zr-nodes. Notably, density functional theory (DFT) study reveals that five-membered “Cu-N-B-C-C” ring is the key species responsible for the hydroboration process with specific selectivity.

Substituent effect of metal porphyrin molecular catalysts plays a crucial role in determining the catalytic activity of oxygen electrocatalysis. Herein, substituent position effect of Co porphyrins on oxygen electrocatalysis, including the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER), was investigated. Two Co porphyrins, namely 2,4,6-OMe-CoP and 3,4,5-OMe-CoP, were selected as the research objects. The ORR and OER performance was evaluated by drop-coating molecular catalysts on carbon nanotubes (CNTs). The resulted 3,4,5-OMe-CoP/CNT exhibited high bifunctional electrocatalytic activities and better long-term stability for both ORR and OER than 2,4,6-OMe-CoP/CNT. Furthermore, when applied in the Zn-air battery, 3,4,5-OMe-CoP/CNT exhibited comparable performance to that with precious metal-based materials. The enhanced catalytic activity may be attributed to the improved charge transfer rate, mass transfer and hydrophilicity. This work provides an effective strategy to further enhance catalytic activity by introducing substituent position effect, which is of great importance for developing more efficient energy-related electrocatalysts.

The electrocatalytic CO2 reduction reaction (CO2RR) has attracted increasing attention in recent years. Practical electrocatalysis of CO2RR must be carried out in aqueous solutions containing electrolytes of alkali metal cations such as sodium and potassium. Although considerable efforts have been made to design efficient electrocatalysts for CO2RR and to investigate the structure–activity relationships using molecular model complexes, only a few studies have been investigated the effect of alkali metal cations on electrocatalytic CO2RR. In this study, we report the effect of alkali metal cations (Na+ and K+) on electrocatalytic CO2RR with Fe porphyrins. By running CO2RR electrocatalysis in dimethylformamide (DMF), we found that the addition of Na+ or K+ considerably improves the catalytic activity of Fe chloride tetrakis(3,4,5-trimethoxyphenyl)porphyrin (FeP). Based on this result, we synthesized an Fe porphyrin N18C6-FeP bearing a tethered 1-aza-18-crown-6-ether (N18C6) group at the second coordination sphere of the Fe site. We showed that with the tethered N18C6 to bind Na+ or K+, N18C6-FeP is more active than FeP for electrocatalytic CO2RR. This work demonstrates the positive effect of alkali metal cations to improve CO2RR electrocatalysis, which is valuable for the rational design of new efficient catalysts.

Porphyrins are an important class of ligands with a tremendous ability to capture metal ions closely related to the rich coordination chemistry of porphyrins. Herein we use this characteristic to develop silica gel grafted derivatives for water remediation applications. Therefore, two porphyrin derivatives, one with three and the other with four mercaptopyridyl units were grafted on silica gel functionalized with 3-aminopropyltriethoxysilane. The new adsorbents Si3PyS and Si4PyS were characterized using a suitable set of techniques confirming the covalent attachment of the porphyrins to the silica surface. Additionally, microscopy and N2 adsorption analysis confirmed the structural integrity and preservation of the mesoporous structure of Si during surface modification. The results show that both hybrid materials exhibit good chemical and thermal stability and an outstanding Cu2+ removal capability, with a chemical adsorption capacity of 176.32 mg g–1 and 184.16 mg g–1, respectively. These materials have also been used in real water and industrial wastewater samples with minimal interference in their adsorption capabilities. Density Functional Theory calculations were performed to confirm the good performance of the hybrid materials Si3PyS and Si4PyS towards metal ions. The functionalization of silica surface with porphyrin-based ligands bearing additional binding motifs drastically improves the adsorption capability of the new hybrids towards metal ions. The presence of pyridyl units brings a meaningful advantage, since both porphyrin core and appended pyridyl groups are able of binding Cu2+ ions with high affinity, contributing to the enhancement of the chelating features of the adsorbents prepared when compared with other ligands supported in silica-based materials. published

Summary The synthesis of multi-walled nanostructures represents a formidable challenge owing to the limitations imposed by existing synthetic strategies. Herein, we report a strategy involving molecular-strain engineering (MSE) for constructing double-walled polyhedra from strained bow-shaped macrocycles called molecular bows (MBs). As a proof of concept, four double-walled tetrahedra have been assembled from L-shaped dual-panels subtending ∼70.5° and producing MBs, which incorporate porphyrin and o-xylylene units, forming strained shape-persistent conformations. The head-to-tail closed-loop stacking of these units, driven by complementary non-covalent bonding interactions, leads to a large porphyrin-lined tetrahedron encapsulating a small o-xylylene-lined tetrahedron. The synergistic aromatic shielding effects emanating from the porphyrin tetrahedron result in the largest upfield chemical shifts of −7.7 ppm for protons and −8.8 ppm for carbons from those for the free dual panels. This demonstration, which features the launching of MSE for constructing sophisticated supramolecular nanostructures, could herald a fresh approach to the fabrication of multi-porphyrin photocatalytic systems.

Owing to their reversibly dynamic features, and the regularity of their architectures, supramolecular organic frameworks (SOFs) have attracted attention as new porous materials. Herein, we propose a smart SOF platform for enhanced photodynamic therapy, where the SOF with a superior mitochondria-targeting capability could be cleaved by reactive oxygen species (ROS) produced by itself for highly enhancing PDT. Moreover, it can further work as a platform for carrying chemo-therapeutic drug doxorubicin for synergistic chemo-photodynamic therapy. The SOF is constructed by combining a tetra-β-cyclodextrin-conjugated porphyrin photosensitizer and a ROS-sensitive thioketal linked adamantane dimer utilizing a host-guest supramolecular strategy. The unique supramolecular framework not only completely resolves the aggregation caused quenching of porphyrin photosensitizers but also endows them with significantly enhanced water-solubility. The in vitro and in vivo results demonstrate that the SOF could be targeted onto mitochondria by confocal imaging, and dissociated by ROS generated by itself, leading to autonomous release of porphyrin photosensitizers and DOX for high anti-cancer activity. It is believed that the strategy using a SOF has the potential of being used to construct versatile agents for combined therapies. Statement of significance Photosensitizers are the essential element in photodynamic therapy. However, typical photosensitizers commonly encounter poor water-solubility, non-specific tumor-targeting, aggregation-caused quenching (ACQ), which seriously reduce PDT efficacy. A mitochondria-targeting and ROS-sensitive supramolecular organic framework (SOF) is designed for photodynamic therapy in cancer treatment, which could completely overcome the bottleneck in the applications of photosensitizers (PSs). The SOF is constructed by combining a tetra-β-cyclodextrin-conjugated porphyrin photosensitizer and a ROS-sensitive thioketal linked adamantane dimer unit utilizing a host-guest supramolecular strategy. The unique supramolecular framework not only completely resolves the aggregation caused quenching of porphyrin photosensitizers but also endows them with significantly enhanced water-solubility. Moreover, the SOF can be readily functionalized to incorporate the anti-cancer agent Doxorubicin and mitochondria targeting molecules through respective physical encapsulation and host-guest interactions.

Hydrogen evolution in the presence of atmospheric level of oxygen is a significant barrier in the quest for an alternative, sustainable and green source of energy to counter the depleting fossil fuel sources and increasing global warming due to fossil fuel burning. Oxygen reduction is thermodynamically more favourable than proton reduction and it often produces reactive oxygenated species upon partial reduction which deactivates the catalyst. Thus, catalyst development is required for efficient proton reduction in the presence of oxygen. Here, we demonstrate an iron porphyrin having triazole containing 2nd sphere hydrogen bonding residues appended with redox active ferrocene moieties (α4-Tetra-2-(3-ferrocenyl-1,2,3-triazolyl)phenylporphyrin (FeFc4)) as a bifunctional catalyst for fast and selective oxygen reduction to water and thus, preventing the proton reduction by the same catalyst from oxidative stress. Fe(0) is the active species for proton reduction in these iron porphyrin class of complexes and it is observed that the kinetics of proton reduction at Fe(0) state occurs at much faster rate than O2 reduction and thus, paving the way for selective proton reduction in the presence of oxygen.

Organic phase change materials (PCMs) have attracted considerable attention for thermal energy storage applications because of their non-toxicity, suitable working temperature range and excellent thermal/chemical stability. However, most traditional organic PCMs have small molecular structures and are prone to leakage during fusion. To address this problem and enhance the shape-stability of organic PCMs, nanosphere-shaped porphyrin-ferrocenyl conjugated microporous polymers (PFCMPs) with high porosity (~ 650 m2/g) were solvothermally synthesized using a Diels-Alder reaction between 1,1′-ferrocenedicarboxaldehyde and pyrrole in the presence of glacial acetic acid and anhydrous Lewis acids (FeCl3, AlCl3, and CuCl2). The PFCMPs were then encapsulated with PCMs, that is, 1-octadecanol (ODA), to prepare the composite materials of ODA@PFCMPs. The optimized composite exhibited a high latent heat (up to 153.8 J/g), excellent reversibility (negligible change in latent heat upon 100 cycles of heating–cooling), good shape stability, and long heat storage durability (425 s), making it a promising candidate for solar thermal energy engineering and management.

The promising photocatalytic conversion of CO2 into valuable fuel promotes the development of photocatalyst through various methods. In this work, TiO2 nanoparticle was composited with covalent porphyrin polymers (COP-Ps) to fabricate composite photocatalysts. The resultant COP-Ps/TiO2 composites by in situ hydrothermal method exhibit much improved photocatalytic activity for the conversion of CO2 into CO relative to two components, and it is attributable to improved charge transfer between two moieties led by strong interaction. Especially, TiO2 is composited more evenly with the sulfonated hollow COP-P (sh-COP-P). The resultant composite sh-COP-P/TiO2 performs best with a CO production rate of 5.70 μmol·g−1·h−1, which is approximately 20.4 times as high as that of pure TiO2 and 2.3 times of sh-COP-P polymer. For comparison, the simple physical mixture of sh-COP-P and TiO2 (sm-sh-COP-P/TiO2) was fabricated, and it performs more badly due to poor mixing uniformity. A Z-scheme photocatalytic mechanism was proposed for sh-COP-P/TiO2 composite on the basis of energy band analysis and hydroxyl radical test. This study provides a new in situ strategy to fabricate organic polymer/metal oxide composites of high photocatalytic activity for CO2 reduction.

A one-pot synthesis method was conceptualized and implemented to develop green carbon-based nanocomposites working as biosensors. Porphyrin was synthesized to adorn the surface of nanocomposites making them highly sensitive for giving rise to π-π interactions between the genetic materials, proteins and porphyrin rings. The hydrogen bond formed between the proteins (analytes) and the nitrogen in the porphyrin structure as well as the surface hydroxyl groups was equally probable. In this context, different forms of porphyrins were incorporated to explore the interrelationship between the surface morphology and the ability of detection of genetic material and/or proteins by the aid of the synthesized structures. This phenomenon was conceptualized to optimize the interactions between the biomolecules and the substrate by reaching significant biosensor application in the presence of Anti-cas9 protein and sgRNA (concentration changed between 10 and 500 n mol/L). Almost full quenching of fluorescence emission was observed after addition of 300 n mol/L of Anti-cas9 protein and 250 n mol/L of sgRNA. Surprisingly, CoNi2S4 provided 12%–29% cytotoxicity in both HEK-293 and PC12 cell lines.

In this article, we report a series of hexanuclear rare-earth MOFs based on Ce (III) and 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin, namely Ce-PCN-224, with a new zln topology through linker induce strategy. Ce-PCN-224 exhibits permanent porosity, high water and thermal stabilities, and the ability to adsorb dye molecules in the aqueous environment. Moreover, after post-metallation with Fe, Co, and Ni, Ce-PCN-224(Fe) and Ce-PCN-224(Co) were proved to be efficient heterogeneous catalysts for the cycloaddition of CO2 with epoxides, attributed to the combination of multiple Lewis acidic sites.

Molecular catalysts for H2-evolution are of interest for their integration into light-harvesting complexes for photocatalytic water splitting. Here, we report the meso-tetra (4-carboxyphenyl) porphine [(TCPP)PtII] complex as a molecular H2-evolving photocatalyst using chloranilic acid (CA) as a sacrificial electron donor, the choice of which is critical to the stability of the photocatalyst. When triethanolamine was used, [(TCPP)PtII] decomposed to form Pt nanoparticles. Density functional theory calculations together with evidence from electrochemical and spectroscopic analyses suggested that the catalysis was possibly initiated by a proton-coupled electron transfer (PCET) to form [(TCPP)PtI]-N-H, followed by another electron injection and protonation to form a [(TCPP)PtII-hydride]-N-H intermediate that can release H2. As the whole catalytic cycle involves the injection of multiple electrons, a light-harvesting network should be helpful by providing multiple photo-induced electrons. Thus, we integrated this molecular catalyst into a light-harvesting metal-organic framework to boost its activity by ~830 times. This work presents a mechanistic study of the photocatalytic H2 evolution and energy transfer and highlights the importance of a light-harvesting network for multiple electron injections.

Electrochemical reduction of CO2 is a promising strategy to manage the global carbon balance by transforming CO2 into chemicals. The efficiency of CO2 electroreduction is largely dependent on the design of hybrid electrode where both support and catalyst govern the performance of the electrolyzer. In this work, TiO2 calcined at different temperatures, was used as a support for immobilization of cobalt tetraphenyl porphyrin (CoTPP) and its effect on CO2 reduction was studied. It is demonstrated that the crystalline phase of TiO2 and doping of TiO2 apparently affecting CO2 electroreduction. It is found that anatase phase exhibits higher activity and selectivity compared to rutile due to the enhanced conductivity which in turn enables faster electron transfer between the support and CoTPP. As for dopants, the carbon doping in anatase TiO2 is proven to further enhance its conductivity, consequently resulting in the enhanced performance. This study implies that the rational design of supports is important for the performance of the hybrid electrode towards electrochemical CO2 reduction.

Summary Photosensitization under near-infrared (NIR) excitation is attractive for applications in photocatalysis and theragnostics because NIR light offers deeper penetration depth through various media, including biological tissues. Nevertheless, most photosensitization processes can only be stimulated by ultraviolet or visible light. Here, we demonstrate a new paradigm, based on the coupling of lanthanide inorganic nanoparticles and organic photosensitizers, for NIR photosensitization through lanthanide-triplet sensitization. We show that the triplet levels of a series of porphyrin and phthalocyanine sensitizers can be effectively populated by energy transfer from lanthanide nanoparticles. This approach allows to directly active lower-lying triplet states of photosensitizers without the need to populate their higher-lying excited singlet states. It enables photosensitization to generate singlet oxygen at ultralow NIR irradiance with over 100-fold improved performance compared with conventional upconversion-based NIR photosensitization, which may provide new opportunities for applications such as deep-tumor phototherapy and NIR-light driven photosynthesis.

This work describes a new ternary nanocomposite of TiO2 nanospheres decorated on the surface of graphitic carbon nitride (C3N4)-porphyrin (TCP) via the sonochemical method (WUC-D22H, Daihan Scientific, Korea). The ultrasonic frequency and power were 20 kHz and 100 W, respectively. The structure and morphology of the synthesized nanocomposites were systematically characterized by FT-IR, XRD, SEM, UV-DRS, and mapping analysis. Compared to its single and binary components, the ternary nanocomposite TiO2@C3N4-TCP clearly shows higher photocatalytic action against Rhodamine B (Rh–B) dye contaminants in the visible region. Ternary nanocomposite TiO2@C3N4-TCP catalysts have good stability and reusability for four successive photocatalytic discoloration tests. These materials consist of synergistic nanocomposites with enhanced visible light adsorption, effective charge separation, and low rate recombination dynamics. In addition, it has been clarified that hydroxyl and superoxide radical active species play some auxiliary roles, whereas the holes play the main role in the photodiscoloration of Rh–B. Moreover, as expected this work presents a novel approach towards advanced ternary nanocomposites in visible light adsorption aimed at the photodecomposition of pollutants via the photocatalytic process.

Manganese porphyrins are well-known protectors against the deleterious effects of pro-oxidant species such as superoxide ions and hydrogen peroxide. The present study investigated the antioxidant cytochrome c-like activities of Mn(III)TMPyP [meso-tetrakis (4-N-methyl pyridinium) porphyrin] against superoxide ion and hydrogen peroxide that remained unexplored for this porphyrin. The association of TMPyP with a model of the inner mitochondrial membrane, cardiolipin (CL)-containing liposomes, shifted +30 mV vs. NHE (normal hydrogen electrode) redox potential of the Mn(II)/Mn(III) redox couple. In CL-containing liposomes, Mn(III)TMPyP was reduced by superoxide ions and recycled by Fe(III)cytochrome c to the oxidized form. Similarly, isolated rat liver mitoplasts added to a sample of Mn(II)TMPyP promoted immediate porphyrin reoxidation by electron transfer to the respiratory chain. These results show that Mn(III)TMPyP can act as an additional pool of Fe(III)cytochrome c capable of transferring electrons that escape from the IV complex back into the respiratory chain. Unlike Fe(II)cytochrome c, Mn(II)TMPyP was not efficient for hydrogen peroxide clearance. Therefore, by reducing cytochrome c, Mn(II)TMPyP can indirectly contribute to hydrogen peroxide elimination.

Herein we report CO2 electrochemical reduction reaction (CO2ERR) on the cobalt tetraphenylporphyrin (CoTPP) modified TiO2 nanotube (TNT) electrode. It was found the axial coordination of drop-casting solvent to CoTPP and the porphyrin structure are the major factors that have significant effects on the catalytic performance of the electrode. As confirmed by spectrophotometric titration, pyridine has a stronger coordination bond to CoTPP than DMF and THF thus leading to the highest efficiency among the drop-casting solvents tested in the study. Based on the spectrophotometric analysis, possible coordination mechanism between drop-casting solvents and CoTPP is put forward. On the other hand, introduction of –COOMe substituents in phenyl rings of CoTPP weakens the coordination bond between pyridine and CoTPP as clearly evidenced by deuterium NMR spectra, resulting in a detrimental effect on CO2ERR. Therefore, the manipulation of the coordination environment around the metal center of immobilized catalyst is crucial in designing an efficient electrocatalytic system.

Summary Air, water, and soil pollution devastate countless ecosystems and deteriorate human health. Adsorption has commonly been used as a pollutant removal technique, but ongoing materials science research is still searching for more efficient, cheaper, and scalable sorbent materials. Herein, we discuss the synthesis and pollutant-capturing abilities of covalent polymeric structures, including covalent organic polymers and covalent organic frameworks that contain organic macrocycles in the backbone of their structures. These organic macrocycles (cyclodextrin, calixarene, cucurbituril, pillararene, and porphyrin) possess cavities and functional groups that can sequester pollutants by forming supramolecular interactions. The insolubility of these materials prominently aids in their regeneration and recyclability potentials. Following a discussion on the synthetic strategies used in the polymerization of each type of macrocycle, environmental applications of these materials are presented. Here, we focus on the removal of micropollutants, charged species, metal ions, oils and organic solvents, perfluorinated substances, iodine, and volatile organic compounds.

Iron-incorporated ordered carbonaceous frameworks (OCFs) have been synthesized by the pyrolysis of iron porphyrin with ethynyl groups as polymerizable/carbonizable moieties at a temperature higher than 600 °C. The pyrolysis behavior is analyzed by thermogravimetry-differential thermal analysis-mass spectrometry, and the obtained carbon materials are characterized by X-ray diffraction, X-ray absorption fine structure, and high-angle annular dark-field scanning transmission electron microscopy. The introduction of ethynyl groups at the meta positions of the peripheral phenyl groups is essential for efficient cross-linking upon thermal polymerization. The thermally stable polymer thus obtained can be transformed into OCFs with high carbonization yield of 93 % at the subsequent carbonization. OCFs possess periodic structural regularity and porphyrin Fe-N4 coordination structure, and exhibit electrocatalysis for the conversion of CO2 into CO.

Transition-metal based M-N4/C catalysts are appealing for electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Employing model catalysts, which have well-defined molecular structures and coordination environments, to investigate electrocatalytic performance of M-N4/C sites for ORR and OER is of fundamental significance. Herein, we reported the use of Co tetra(phenyl)porphyrin 1 and Co tetra(pentafluorophenyl)porphyrin 2 as models to probe the role of Co-N4/C sites for oxygen electrocatalysis. We showed that Co porphyrin 1 is more efficient than its structural analogue 2 for oxygen electrocatalysis in alkaline aqueous solutions, indicating that the electron-rich Co-N4/C site is more favored when noncovalently adsorbed on carbon supports. This work inspires rational design of reaction-oriented catalysts for sustainable energy storage and conversion technologies.

Manganese (III) complex with meso-5,10,15,20-Tetrakis(2,5-dimethoxy-phenyl) porphyrin, Mn[T(2,5-(OCH3)2)PP], has been prepared utilizing meso-5,10,15,20-Tetrakis(2,5-dimethoxyphenyl)porphyrin, [T(2,5-(OCH3)2)PP], and Manganese (II) acetate by complexation method. The prepared complex is characterized by UV–Vis spectrophotometric and cyclic voltammetric (CV) studies. The formation of Mn(III) porphyrin complex may be due to a significant metal-porphyrin π interaction. In Mn(III) porphyrin, Mn is in high spin d4 configuration. The strongest σ bonding amongst the Mn and the porphyrin with four pyrrole nitrogen donors is responsible for the octahedral geometry. The change in geometry of the complex from octahedral to tetragonal is due to the presence of two axial amines supplied by the addition of secondary amine. Addition of primary amine leads to the formation of square pyramidal Mn(II) porphyrin, wherein the central metal atom is in high-spin d5 configuration with the occupied d(x2-y2) orbital whose orbital energy is low. This indicates that Mn(III) will be out of the plane of porphyrin. The change in the oxidation state of the central manganese atom and shape of the complex were supported by UV–Vis spectrophotometric studies. Cyclic voltammogram confirmed the oxidation and reduction behaviors of Mn porphyrin complex and the oxidation of Mn(III) into Mn(IV) at 0.3209 V.

Cytochrome P450 55A3 (CYP55A3) is an enzyme with the catalytic activity of nitric oxide (NO) to nitrous oxide using NADH or NADPH as the electron donor. Herein CYP55A3 has been expressed in E. coli and purified by His-tag columns. The electrochemical and spectroscopic characteristic of CYP55A3 and its interaction with NO has been studied. The direct electrochemistry of Fe3+/Fe2+ redox peaks in CYP55A3 was realized on the pyrolitic graphite electrode with the redox potential of −475 mV in pH 7.0 phosphate buffer. With the addition of NO a ferric nitroxyl complex (Fe3+-NO) formed with a new reduction peak at −0.78 V. The reduction peak current increased with the concentration of NO and showed typical Michaelis-Menten kinetic characteristics with the apparent Michaelis constant Kmapp 9.78 μM. The binding constant K calculated to be 3.93 × 104 M by UV–vis method. The fluorescence emission spectra of iron porphyrin in CYP55A3 showed with the peak wavelength 633 nm, and its fluorescence intensity increased after binding with NO. The fluorescence analysis demonstrated that NADH can relay electrons to iron porphyrin and reduce NO. The reductive product of NO released and the iron porphyrin in CYP55A3 turned back to the original form.

We report here a straightforward reductive approach for the deoxygenation, activation and functionalization of ultrashort single-walled carbon nanotubes (us-SWCNTs). Us-SWCNTs with lengths of only 20–50 nm were prepared by the low-temperature oxidative-cutting process which inevitably introduced oxygen-containing groups onto the nanotube framework. For the subsequent deoxygenation, six routes have been investigated and the reduction with potassium is the optimal one that can efficiently remove the oxidized groups and consequently recover the inherent structures and properties of us-SWCNTs. This reductive approach permits at the same time very efficient activation of the chemically inert nanotubes by generating the intermediate us-SWCNTn- carbanions. Subsequent quenching these negative charges on the nanotube backbone using electrophiles affords very efficient covalent binding of distinct building blocks as porphyrin, phenyl or hexyl moieties onto us-SWCNTs. Additionally, the Birch-type reductive approach was also performed to realize the first hydrogenation of us-SWCNTs by using water as proton source and lithium as reducing agent.

Summary Due to the existing challenges in the synthesis of covalently linked large organic cages, the potential benefits of such gigantic structures have been less explored, comparatively. Here, we present a one-pot, template-free strategy to construct a porphyrin-based gigantic organic cage P12L24, built with 12 square-shaped porphyrins (P) and 24 bent linkers (L). Single crystal X-ray analysis of P12L24 revealed a cuboctahedron structure with a diameter of ∼5.3 nm reminiscent of the COPII protein with a cuboctahedral geometry. To the best of our knowledge, it represents the largest, pure organic synthetic cage reported so far. By virtue of its large voids facilitating mass transport of substrates, 3a efficiently catalyzes the photooxidation of dihydroxynaphthalene derivatives in a heterogeneous setting, corroborating the benefits of these structures. Additionally, we demonstrate the insertion of a linear guest molecule into Zn-metallated cage Zn-3b in solution, which may facilitate the synthesis of multivariate gigantic cages in the future.

Porphyrias are a group of congenital errors in porphyrin metabolism and in the heme biosynthetic pathway. Accumulation of porphyrin precursors (delta-aminolaevulinic acid and porphobilinogen) is responsible for the neurovisceral crises of acute porphyria, which, when expressed clinically, start with intense abdominal pain. During crises, the urinary elimination of porphobilinogen and delta-aminolaevulinic acid is always very high. Excessive porphobilinogen concentration in urine is easily identified using the simple Hoesch test. A negative test rules out a current porphyric crisis. The clinical protocol for patients with acute abdominal pain of unknown origin in whom a positive Hoesch test leads to the suspicion of acute porphyria is based on the following aspects: initial clinical assessment in the emergency department, suppression of potential triggers, specific treatment for the crisis with hemin and/or glucose overload and symptomatic treatment.

Design and synthesis of highly active and durable electrocatalysts toward oxygen reduction reaction (ORR) is of particular importance for proton exchange membrane fuel cells (PEMFCs), yet remains a grand challenge. Herein, we report the deposition of iron (III) porphyrin (FeP) on house-made Pt/C by rotary evaporation of the mixture of FeP and house-made Pt/C dispersed in chloroform, followed by pyrolysis at 650 °C in argon atmosphere. This approach led to the synthesis of new non-precious metal electrocatalyst (NPME)-Pt/C composites (Pt/C–FeP) with an average nanoparticle diameter of 3.1 ± 1.5 nm without aggregation. According to X-ray photoelectron spectroscopy (XPS), the binding energy of Pt 4f7/2 became larger due to the presence of pyrolyzed FeP. In addition, the electrochemically active surface area (ECSA) of Pt/C–FeP-650 is 65 m2/g less than that of house-made Pt/C (80.2 m2/g). This implies that the pyrolyzed FeP may have partially covered the surface of Pt nanoparticles and thus lowering the ECSA. Interestingly, the mass activity (MA) of Pt/C–FeP turns out to be 349.0 mA/mgPt @0.9 V vs. RHE, which is 2.6 times and 1.5 times of house-made Pt/C and commercial Pt/C, respectively. It is speculated that the electronic interaction and possible synergy between Pt and pyrolyzed FeP as NPME might have contributed to the ORR activity improvement despite of partial loss of ECSA. During accelerated durability tests (ADTs), the MA of Pt/C–FeP-650 degrades 64.3% inferior to commercial Pt/C (52.2%). The main reason likely arises from the degradation of pyrolyzed FeP, which is a bottleneck problem confronting NPMEs.

In water–DMF at DMF content less than 2.6 mol dm−3, deuteroporphyrin IX dimethyl ester forms both H- and J-aggregates. The J-aggregates are detected as a single type of associated species after binding of the porphyrin with BSA on the surface of the protein IB subdomain.

Superoxide-initiated anion-radical electrodeposition from solutions in DMSO was used to obtain smooth compact films of poly-5,10,15,20-tetrakis(4-hydroxyphenyl)porphyrin having a photovoltaic response.

High active and low expensive electrocatalysts for methanol oxidation reaction (MOR) still remain a signification challenge for large-scale commercial application of direct methanol fuel cells (DMFCs). Herein, the photoelectrocatalytic activity of cobalt sulfide (CoS) nanosheets are dramatically developed towards MOR by introduction of a photosensitive organic molecule (5, 10, 15, 20-tetrakis(4-achlorophenyl)porphyrin (TClPP). CoS/TClPP exhibits a high mass activity of 1188 mA mg−1 for MOR under visible light irradiation, which is 1.6 times higher than that of pure CoS under dark as well as 1.37 times higher than that of pure CoS under visible light. The photoelectrocatalytic mechanism of CoS/TClPP is ascribed to the effective inhibiting of recombination of photoelectrons and holes as well as acceleration of electron transfer, which are verified by photoluminescence (PL) emission spectra, photocurrent response curves and UV–vis diffuse reflectance spectra (DRS), respectively. The low cost, highly stable and active CoS/TClPP as a noble-metal-free anode photoelectrocatalyst has a potential application in DMFCs.

Transparent-conductive-oxide-free (T-C-O-free) back-contact (B-C) dye-sensitized solar cell (DSC) utilizing flexible Stainless Steel (SS) mesh (SS-mesh) supported with mesoporous TiO2 as a photoanode employing cobalt electrolyte is being presented. A thin layer of Ti metal over the SS-mesh was ascertained to be essential to retard the back electron reaction, which was confirmed by the dark current measurements. The interfacial contact between the SS-mesh and nanoporous (NP) TiO2 of the photoanode of T-C-O-free B-C-DSC was driven to influence the photovoltaic performance greatly. It was confirmed by electrochemical impedance analysis that NP TiO2 of 30 nm exhibited less charge transfer impedance observed at TiO2-dye-electrolyte interface as compared to TiO2 of having particle size of 15–20 nm. T-C-O-free B-C-DSC employing dye mixer combination of indoline dyes D-131 and D-205 (1:1) with relatively larger NP of TiO2 (30 nm) as compared to TiO2 of 15–20 nm exhibited enhanced photoconversion efficiency (PCE) of 4.02%. To increase the PCE even further, T-C-O-free B-C-DSC with cobalt based electrolyte sensitized with porphyrin (YD2-o-C8)-dye bearing a larger optical window was investigated. An optimized 10 µm thickness of the TiO2 layer was found to be optimum leading to an enhanced PCE of 5.26%.

Crystalline, electrically conductive molecules that transport charge carriers efficiently are candidates for next–generation printable optoelectronic devices. Here, we have designed a series of D-π-D porphyrin molecular systems as either a free-base or with coordinated metals (Cu and Zn) via high yield, low-temperature synthetic procedures. The D-π-D porphyrin molecular systems (coded as HPPHT, CPPHT and ZPPHT) were comprehensively investigated employing electrical and electrochemical methods, optical absorption spectroscopy, XRD, and XPS to identify their energy levels, optical, electrical and structural properties. The studies revealed that the D-π-D porphyrin molecular systems were crystalline, with desirable energy levels and superior electrical properties compared to the benchmark Spiro-OMeTAD under similar conditions. Among these molecular systems, CPPHT exhibited an activation energy of 0.13 eV and a higher charge carrier density (Nd ~ 4.84 × 1013 cm−3), when compared to the HPPHT (4.20 × 1011 cm−3, 0.13 eV) and ZPPHT (1.92 × 1012 cm−3, 0.17 eV) systems. These molecular systems were introduced as hole transport materials into pre-made perovskite solar cells (without a HTM) by a simple infiltration process via the front contact layer. Among the three systems studied, CPPHT solar cells showed the highest photo-current density (Jsc) of 20.44 mA·cm−2 and power conversion efficiency (PCE) of 11.76% when compared with the H/ZPPHT devices under AM 1.5G (100 mW·cm−2) illumination; signifying lower recombination at the interface of the CPPHT/perovskite (MAPbI3). Incorporation of Li-TFSI/t-BP additives on the device surface improved the HTM-MAPbI3 interface, and increased the Jsc to 21.35 mA·cm−2 with a PCE of 12.88% for CPPHT devices. These D-π-D porphyrin molecular systems under ambient conditions demonstrated excellent short-term and operational stability in the presence of moisture. The modified device architecture opens up a novel configuration for designing high–performance optoelectronic devices.

Metal porphyrins have received sustained attention due to their remarkable catalytic properties. However, the catalytic activities of porphyrins are still moderate for oxygen reduction /evolution (ORR/OER) due to the high binding energies between the catalyst and reactant. Herein, we propose a novel strategy to modulate the binding energies of the oxygenated intermediates by introducing electron coupling between the substrate and the metal porphyrin. Our results reveal remarkable enhancement of OER/ORR performance when the Co-porphyrin molecule is supported on the graphene/Ni (111) substrate. The ORR/OER overpotentials can be greatly reduced, in particular for ORR from 0.6 V to 0.31 V. The enhanced ORR/OER activity of Co-porphyrin/graphene/Ni system stems from the electronic coupling between the catalyst and the substrate that modulates the binding strength between catalytic active sites and the reaction intermediates. Our study represents an efficient strategy to design low-cost, high performance, bifunctional electrocatalysts for the application in rechargeable metal-air batteries.

Summary Drawing inspiration from nature today remains a time-honored means of discovering the therapies of tomorrow. Porphyrins, the so-called “pigments of life” have played a key role in this effort due to their diverse and unique properties. They have seen use in a number of medically relevant applications, including the development of so-called drug conjugates wherein functionalization with other entities is used to improve efficacy while minimizing dose limiting side effects. In this Perspective, we highlight opportunities associated with newer, completely synthetic analogs of porphyrins, commonly referred to as porphyrinoids, as the basis for preparing drug conjugates. Many of the resulting systems show improved medicinal or site-localizing properties. As befits a Perspective of this type, our efforts to develop cancer-targeting, platinum-containing conjugates based on texaphyrins (a class of so-called “expanded porphyrins”) will receive particular emphasis; however, the promise inherent in this readily generalizable approach will also be illustrated briefly using two other common porphyrin analogs, namely the corroles (a “contracted porphyrin”) and porphycene (an “isomeric porphyrin”).

β-Chlorination of meso-tetraphenylporphyrin, H2TPP leads to the formation of H2TPPClx (X = 2, 4, 6 and 8) with absorption bands in the range of 421–451 and 650–715 nm, for the Soret and Q(0,0) bands, respectively. H2TPPClx were used as photosensitizers for the aerobic photooxidation of cyclooctene under mild conditions and compared with that of the non-chlorinated porphyrin. The lowest degree of catalyst degradation was observed in the case of H2TPPCl2. H2TPPCl2 and H2TPPCl4 showed the highest photocatalytic activity among the series. In spite of the electron-withdrawing effects of the chlorine atoms, with the exception of H2TPPCl2, the chlorinated porphyrins showed a comparable oxidative degradation to that of H2TPP towards oxidative degradation. The preference of blue LED lamp over the red one shows that the absorption at the Soret band region of the chlorinated porphyrins is mainly responsible for the photosensitizer ability of the catalyst. In this regard, H2TPPCl2 and H2TPPCl4 which have the highest overlap with the emission bands of the blue LED lamp showed the highest photocatalytic activity than the other H2TPPClx and H2TPP. Also, control reactions performed in the presence of 1,3-diphenylisobenzofuran and 1,4-benzoquinone provided evidence for the involvement of singlet oxygen as the main reactive oxygen species in this reaction. Singlet oxygen quantum yields (φF) of H2TPPClx were smaller than that of the non-chlorinated porphyrin and decreased as H2TPPCl8 > H2TPPCl4 > H2TPPCl6 ≥ H2TPPCl2. H2TPPClx showed much higher photocatalytic activities than their brominated counterparts. Also, the φF values and oxidative stability of the chlorinated porphyrins were usually higher than those of the brominated porphyrins, with the same degree of β-halogenation. Protonation of H2TPPClx with weak and strong acids (HCOOH, CF3COOH and HCl), also their immobilization on a nano-structured acidic polymer (Amberlyst 15) were used to study the influence of core protonation on photocatalytic activity and oxidative stability of the chlorinated porphyrins.

A hybrid film of chitosan/poly(vinyl alcohol)/cationic Fe(III)-porphyrin (Cht/PVA-FeTMPyP) was synthesized to act as a Fenton-like catalyst to decolorize methyl orange and methyl red azo dyes. The Cht/PVA-FeTMPyP film was characterized by different analytical and microscopy techniques, which indicated that the metalloporphyrin affects different properties of the hybrid film. Batch experiments revealed that the hybrid film exhibits enhanced catalytic activity towards dyes decolorization in the presence of H2O2 as compared to the “free” FeTMPyP. Fast decolorization rates as high as 90 min were observed for both azo dyes under mild conditions (pH 7 and room temperature), even at low concentrations of the catalyst in H2O2. After the decolorization, FTIR analysis showed that simple molecules are released as by-products. Moreover, the hybrid film performed well in cyclic runs without leaching out iron ions or losing its catalytic activity. All these features associated with its ease handling ranks the Cht/PVA-FeTMPyP hybrid film as a promising heterogeneous Fenton-like catalyst for the decomposition of azo dyes in water.