Porphyrin Networks Research Articles

Boosted hydrogen evolution reaction for a nitrogen-rich azo-bridged metallated porphyrin network

The potential of porous organic polymers (POPs) toward electrocatalytic water splitting have attracted considerable scientific attention, due to their high specific surface areas, superlative porosity and diverse electronic structures; yet it remains challenging. Herein, we report a facile synthesized novel nitrogen-rich azo-bridged metallated porphyrin POP (CoTAPP-CoTNPP) for improving the hydrogen evolution reaction (HER) activity. The incorporation of the cobalt porphyrins and the azo groups endows CoTAPP-CoTNPP with effective charge transfer efficiency and large π-conjugated porous frameworks, thus enhancing the HER performance. Origins of the excellent HER performance of the material are evaluated using a series of structural and electrochemical measurements. Remarkably, CoTAPP-CoTNPP exhibits low overpotentials of 103 and 170 mV to reach 10 mA cm−2 in acidic and alkaline media, respectively, outperforming many previously reported HER electrocatalysts. These results demonstrate the enormous potential of the as-prepared azo-linked porphyrin POP for electrocatalytic water splitting.

#5050 ANTIOXIDANT PORPHYRIN-BASED NANOZYME WITH SINGLE RUTHENIUM FOR TREATMENT OF ACUTE KIDNEY INJURY

Abstract Background and Aims Acute kidney injury (AKI) describes a sudden loss of kidney function characterized by elevated serum creatinine (CRE) levels and reduced urinary output. AKI patients have a high mortality rate, but limited treatment options are currently available. During the AKI progression, an excess of reactive oxygen species (ROS) leads to oxidative stress, which often results in cell damage and renal failure. Therefore, ROS scavenging has been considered a promising strategy for AKI treatment. Here we report a porphyrin-based nanozyme with single ruthenium (Por-Ru) as a ROS scavenger to cure AKI. Method The Por-Ru nanozyme was synthesised by one-pot synthesis. First, the 5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (Por) was added to the solvent containing N, N-dimethylformamide. The RuCl3 was then introduced to form Ru-N coordinated porphyrin networks. We analysed the morphology and chemical structure using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). We also tested its enzyme-mimicking abilities to scavenge ROS. The catalase-like (CAT) property was tested using a peroxide-titanium complex method, and the superoxide dismutase-like (SOD) property was tested using a •O2− scavenging assay. In vitro, the protective effect of Por-Ru nanozyme against ROS damage was examined using the mouse tubular epithelial (TCMK-1) cell line. After biocompatibility evaluation, the therapeutic efficacy of Por-Ru nanozyme was investigated in glycerol-induced AKI mice. Results 1. Characterizations of Por-Ru nanozyme: The SEM image showed the Por-Ru nanozyme was spherical with an average diameter of 6-8 nm (Figure 1a). Meanwhile, the XPS revealed the presence of Ru and showed the detailed elemental components (Figure 1b). As shown in Figures 1c and d, the Por-Ru nanozyme had excellent CAT-like and SOD-like capabilities. Furthermore, the DPPH• assay confirmed the antioxidant property (Figure 1e). 2. Protective effect of Por-Ru nanozyme in vitro and in vivo: The results of cell counting kit-8 assay showed that Por-Ru nanozyme was not cytotoxic to TCMK-1 cells at concentrations ranging from 10 to 100 µg/mL. We further examined the cytoprotective effects of Por-Ru nanozyme against ROS damage. The flow cytometry results showed that the intracellular ROS level increased after treatment with H2O2, while the ROS level obviously decreased with the addition of Por-Ru nanozyme (Figure 2a, b). The protective effect of Por-Ru nanozyme against H2O2-induced apoptosis was also investigated. As shown in Figures 2c and d, the rate of cell apoptosis was significantly reduced with the addition of Por-Ru nanozyme. Before the in vivo experiments, the haemolysis rate of Por-Ru nanozyme was examined and found to be less than 5% even at a dose of 200 µg/mL. Additionally, the in vivo toxicity assessment showed that Por-Ru nanozyme at test concentrations had no noticeable impacts on blood parameters, liver and kidney functions, and histopathology of major organs in normal mice. Then, we tested the therapeutic effect of Por-Ru nanozyme in AKI mice. As shown in Figures 2e and f, the CRE and blood urea nitrogen (BUN) levels of AKI mice treated with Por-Ru nanozyme were significantly lower than those of AKI mice group. Additionally, the results of haematoxylin and eosin (H&E) staining showed that many casts (marked as triangles) were observed in the kidney tissue of AKI mice, whereas no obvious damage area was found in AKI mice after the treatment of Por-Ru nanozyme. Conclusion Our findings demonstrate that the Por-Ru nanozyme has excellent anti-ROS enzyme-mimicking capabilities. In vitro experiments revealed that Por-Ru nanozyme alleviated ROS-induced cell apoptosis. In AKI mice, Por-Ru nanozyme effectively improved renal function and attenuated renal tissue damage. Taken together, Por-Ru nanozyme may become a novel agent for AKI treatment.

Ag Nanoparticles Anchored on Nanotubular Porous Porphyrin Networks for Carboxylative Cyclization of Propargyl Alcohols with CO2

AbstractA nanotubular porous porphyrin‐based network (NT‐PPN) was prepared through Friedel–Crafts alkylation polyreaction of meso‐tetraphenylporphyrin iron chloride and subsequent demetalization reaction with concentrated hydrochloric acid. As a superior support, NT‐PPN was decorated with Ag nanoparticles to generate the desired catalyst (Ag@NT‐PPN). Ag@NT‐PPN had a high BET surface area with plentiful hierarchical porosity, considerable CO2 adsorption uptake, as well as high CO2/N2 adsorption selectivity. In the presence of 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU), Ag@NT‐PPN exhibited excellent catalytic performance for the solvent‐free synthesis of α‐alkylidene cyclic carbonates from propargyl alcohols and CO2 at 30 °C. Ag@NT‐PPN also displayed robust constancy, excellent recyclability, and acceptable substrate expansibility for this reaction. Moreover, low concentration of CO2 derived from mixed gas (15% CO2+85% N2 in volume) was positively amenable to this catalytic protocol. This work might offer an opportunity to design metal NPs‐based heterogeneous catalysts and provide a promising candidate for application in the transformation of CO2 into valuable cyclic carbonates.

Structural Transformation of Surface-Confined Porphyrin Networks by Addition of Co Atoms.

The self‐assembly of a nickel‐porphyrin derivative (Ni‐DPPyP) containing two pyridyl coordinating sites and two pentyl chains at trans meso positions was studied with scanning tunneling microscopy (STM), X‐ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) on Au(111). Deposition of Ni‐DPPyP onto Au(111) gave rise to a close‐packed network for coverages smaller or equal to one monolayer as revealed by STM and LEED. The molecular arrangement of this two‐dimensional network is stabilized via hydrogen bonds formed between the pyridyl's nitrogen and hydrogen atoms from the pyrrole groups of neighboring molecules. Subsequent deposition of cobalt atoms onto the close‐packed network and post‐deposition annealing at 423 K led to the formation of a Co‐coordinated hexagonal porous network. As confirmed by XPS measurements, the porous network is stabilized by metal‐ligand interactions between one cobalt atom and three pyridyl ligands, each pyridyl ligand coming from a different Ni‐DPPyP molecule.

Restructuring of Porphyrin Networks Driven by Self-Assembled Octanoic Acid Monolayer on Au(111).

We report time-dependent surface restructuring of bicomponent domain structures of 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (H2OEP) and cobalt(II) 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine (CoOEP) (H2/Co OEP) driven by self-assembled octanoic acid on the surface of Au(111). Scanning tunneling microscopy (STM) visualized molecular adsorption/desorption and rearrangement of supramolecular architectures in real-time in a solution of octanoic acid. We found that unique domain structures emerged at an initial state guided by adsorbed octanoic acid on the Au surface. Moreover, the desorption of octanoic acid occurred in solution, leading to the surface restructuring of porphyrin molecular networks. This molecular evidence is well-manifested in the time-dependent phase transitions, monitored by in situ STM.

Orthogonal Coordination Chemistry of PTA toward Ru(II) and Zn(II) (PTA = 1,3,5-Triaza-7-phosphaadamantane) for the Construction of 1D and 2D Metal-Mediated Porphyrin Networks.

This work demonstrates that PTA (1,3,5-triaza-7-phosphaadamantane) behaves as an orthogonal ligand between Ru(II) and Zn(II), since it selectively binds through the P atom to ruthenium and through one or more of the N atoms to zinc. This property of PTA was exploited for preparing the two monomeric porphyrin adducts with axially bound PTA, [Ru(TPP)(PTA-κP)2] (1, TPP = meso-tetraphenylporphyrin) and [Zn(TPP)(PTA-κN)] (3). Next, we prepared a number of heterobimetallic Ru/Zn porphyrin polymeric networks—and two discrete molecular systems—mediated by P,N-bridging PTA in which either both metals reside inside a porphyrin core, or one metal belongs to a porphyrin, either Ru(TPP) or Zn(TPP), and the other to a complex or salt of the complementary metal (i.e., cis,cis,trans-[RuCl2(CO)2(PTA-κP)2] (5), trans-[RuCl2(PTA-κP)4] (7), Zn(CH3COO)2, and ZnCl2). The molecular compounds 1, 3, trans-[{RuCl2(PTA-κ2P,N)4}{Zn(TPP)}4] (8), and [{Ru(TPP)(PTA-κP)(PTA-κ2P,N)}{ZnCl2(OH2)}] (11), as well as the polymeric species [{Ru(TPP)(PTA-κ2P,N)2}{Zn(TPP)}]∞ (4), cis,cis,trans-[{RuCl2(CO)2(PTA-κ2P,N)2}{Zn(TPP)}]∞ (6), trans-[{RuCl2(PTA-κ2P,N)4}{Zn(TPP)}2]∞ (9), and [{Ru(TPP)(PTA-κ3P,2N)2}{Zn9(CH3COO)16(CH3OH)2(OH)2}]∞ (10), were structurally characterized by single crystal X-ray diffraction. Compounds 4, 6, 9, and 10 are the first examples of solid-state porphyrin networks mediated by PTA. In 4, 6, 8, 9, and 11 the bridging PTA has the κ2P,N binding mode, whereas in the 2D polymeric layers of 10 it has the triple-bridging mode κ3P,2N. The large number of compounds with the six-coordinate Zn(TPP) (the three polymeric networks of 4, 6 and 9, out of five compounds) strongly suggests that the stereoelectronic features of PTA are particularly well-suited for this relatively rare type of coordination. Interestingly, the similar 1D polymeric chains 4 and 6 have different shapes (zigzag in 4 vs “Greek frame” in 6) because the {trans-Ru(PTA-κ2P,N)2} fragment bridges two Zn(TPP) units with anti geometry in 4 and with syn geometry in 6. Orthogonal “Greek frame” 1D chains make the polymeric network of 9. Having firmly established the binding preferences of PTA toward Ru(II) and Zn(II), we are confident that in the future a variety of Ru/Zn solid-state networks can be produced by changing the nature of the partners. In particular, there are several inert Ru(II) compounds that feature two or more P-bonded PTA ligands that might be exploited as connectors of well-defined geometry for the rational design of solid-state networks with Zn–porphyrins (or other Zn compounds).

Salt bridges govern the structural heterogeneity of heme protein interactions and porphyrin networks: microperoxidase-11.

In this work, a proteolytic digest of cytochrome c (microperoxidase 11, MP-11) was used as a model to study the structural aspects of heme protein interactions and porphyrin networks. The MP-11 structural heterogeneity was studied as a function of the starting pH (e.g., pH 3.1–6.1) and concentration (e.g., 1–50 μM) conditions and adduct coordination. Trapped ion mobility spectrometry coupled to mass spectrometry (TIMS-MS) showed the MP-11 structural dependence of the charge state distribution and molecular ion forms with the starting pH conditions. The singly charged (e.g., [M]+, [M − 2H + NH4]+, [M − H + Na]+ and [M − H + K]+) and doubly charged (e.g., [M + H]2+, [M − H + NH4]2+, [M + Na]2+ and [M + K]2+) molecular ion forms were observed for all solvent conditions, although the structural heterogeneity (e.g., number of mobility bands) significantly varied with the pH value and ion form. The MP-11 dimer formation as a model for heme-protein protein interactions showed that dimer formation is favored toward more neutral pH and favored when assisted by salt bridges (e.g., NH4+, Na+ and K+vs. H+). Inspection of the dimer mobility profiles (2+ and 3+ charge states) showed a high degree of structural heterogeneity as a function of the solution pH and ion form; the observation of common mobility bands suggest that the different salt bridges can stabilize similar structural motifs. In addition, the salt bridge influence on the MP-11 dimer formations was measured using collision induced dissociation and showed a strong dependence with the type of salt bridge (i.e., a CE50 of 10.0, 11.5, 11.8 and 13.0 eV was observed for [2M + H]3+, [2M − H + NH4]3+, [2M + Na]3+ and [2M + K]3+, respectively). Measurements of the dimer equilibrium constant showed that the salt bridge interactions increase the binding strength of the dimeric species.

Morphology and Size-Dependent Visible-Light-Driven Photocatalytic Hydrogen Evolution of Porphyrin Assemblies

ABSTRACTPhotocatalytic water splitting to form hydrogen can effectively alleviate energy and environmental problems attracting wide attention. However, the current photocatalysts have low photocatalytic efficiencies due to the narrow absorption spectrum, which is far from the actual application requirements. Herein, we use the as-prepared zinc porphyrin self-assemblies to visible-light-drive photocatalytic hydrogen evolution with Pt as the cocatalyst and ascorbic acid (AA) as the sacrificial agent. The results exhibit morphology-dependent performance and hexagonal stacks achieved optimal H2 evolution rate (47.1 mmol/h/g), then followed by nanodiscs, nanorod and tetragonal stacks, meanwhile the nanorods with different aspect ratios show size-dependent properties. The UV-vis absorption and photoluminescence spectra and the shortening of decay time of the corresponding ZnTPyP aggregates reveal that the well-defined self-assembled porphyrin networks are J-aggregation and boost efficient energy transfer with respect to monomer. Such porphyrin self-assemblies are standing for one of the most promising photosensitizers in photocatalysis field and provide an important reference for designing the next generation of hydrogen production.

Coverage-Dependent Structural Transformation of Cyano-Functionalized Porphyrin Networks on Au(111) via Addition of Cobalt Atoms.

The self-assembly process of a cobalt-porphyrin derivative (Co-TCNPP) containing cyanophenyl substituents at all four meso positions on Au(111) was studied by means of scanning tunneling microscopy (STM) and low energy electron diffraction (LEED) under ultrahigh vacuum conditions. Deposition of Co-TCNPP onto Au(111) gave rise to the formation of a close-packed H-bonded network, which was independent of coverage as revealed by STM and LEED. However, a coverage-dependent structural transformation took place upon the deposition of Co atoms. At monolayer coverage, a reticulated long-range ordered network exhibiting a distinct fourfold Co coordination was observed. By reduction of the molecular coverage, a second metal–organic coordination network (MOCN) was formed in coexistence with the fourfold Co-coordinated network, that is, a chevron structure stabilized by a simultaneous expression of H-bonding and threefold Co coordination. We attribute the coverage-dependent structural transformation to the in-plane compression pressure exerted by the molecules deposited on the surface. Our study shows that a subtle interplay between the chemical nature of the building blocks (molecules and metallic atoms) and molecular coverage can steer the formation of structurally different porphyrin-based MOCNs.

Supramolecular Light-Harvesting Antennas of Metal-Coordinated Bis(8-Hydroxyquinoline)-Substituted Porphyrin Networks.

Artificial antenna complexes of metal-coordinated bis(8-hydroxyquinoline)-substituted porphyrin networks that mimic antenna chromophores in plants were organized on titanium dioxide electrodes in photoelectrochemical cells. The generated photocurrents can be optimized according to the two ways of porphyrin self-assembly due to the "antenna effect": changing the number of assembled porphyrin monolayers and the number of generations of the metal-coordinated porphyrin networks.

Microporous Porphyrin Networks Mimicking a Velvet Worm Surface and Their Enhanced Sensitivities toward Hydrogen Chloride and Ammonia.

This work shows that the functions of microporous organic network materials can be enhanced through engineering of the material structure. Mimicking the surface structure of velvet worms, we prepared the aligned 1D structure (rod) of microporous porphyrin networks by the Sonogashira coupling of tetrakis(4-ethynylphenyl)porphyrin with 1,4-diiodobenzene in an anodic aluminum oxide plate. The length of the 1D structure was controlled in the range of 1-5 μm. The velvet worm surface-like microporous porphyrin networks (Velvet-MPNs) showed higher sensitivities to hydrogen chloride and ammonia gases by up to ∼14 and 4.6 times, respectively, compared with a control MPN material without rods.

Self-Assembled One-Dimensional Porphyrin Nanostructures with Enhanced Photocatalytic Hydrogen Generation.

There has been a widespread interest in the preparation of self-assembled porphyrin nanostructures and their ordered arrays, aiming to emulate natural light harvesting processes and energy storage and to develop new nanostructured materials for photocatalytic process. Here, we report controlled synthesis of one-dimensional porphyrin nanostructures such as nanorods and nanowires with well-defined self-assembled porphyrin networks that enable efficient energy transfer for enhanced photocatalytic activity in hydrogen generation. Preparation of these one-dimensional nanostructures is conducted through noncovalent self-assembly of porphyrins confined within surfactant micelles. X-ray diffraction and transmission electron microscopy results reveal that these one-dimensional nanostructures contain stable single crystalline structures with controlled interplanar separation distance. Optical absorption characterizations show that the self-assembly enables effective optical coupling of porphyrins, resulting in much more enhanced optical absorption in comparison with the original porphyrin monomers, and the absorption bands red shift to more extensive visible light spectrum. The self-assembled porphyrin network facilitates efficient energy transfer among porphyrin molecules and the delocalization of excited state electrons for enhanced photocatalytic hydrogen production under visible light.

PH-Dependent Assembly of Porphyrin-Silica Nanocomposites and Their Application in Targeted Photodynamic Therapy.

Structurally controlled nanoparticles, such as core-shell nanocomposite particles by combining two or more compositions, possess enhanced or new functionalities that benefited from the synergistic coupling of the two components. Here we report new nanocomposite particles with self-assembled porphyrin arrays as the core surrounded by amorphous silica as the shell. The synthesis of such nanocomposite nanoparticles was conducted through a combined surfactant micelle confined self-assembly and silicate sol-gel process using optically active porphyrin as a functional building block. Depending on kinetic conditions, these particles exhibit structure and function at multiple length scales and locations. At the molecular scale, the porphyrins as the building blocks provide well-defined macromolecular structures for noncovalent self-assembly and unique chemistry for high-yield generation of singlet oxygen for photodynamic therapy (PDT). On the nanoscale, controlled noncovalent interactions of the porphyrin building block result in an extensive self-assembled porphyrin network that enables efficient energy transfer and impressive fluorescence for cell labeling, evidenced by absorption and photoluminescence spectra. Finally, the thin silicate shell on the nanoparticle surface allows easy functionalization, and the resultant targeting porphyrin-silica nanocomposites can selectively destroy tumor cells upon receiving light irradiation.

A molecular approach to an electrocatalytic hydrogen evolution reaction on single-layer graphene.

A major challenge in the development of electrocatalysts is to determine a detailed catalysis mechanism on a molecular level for enhancing catalytic activity. Here, we present bottom-up studies for an electrocatalytic hydrogen evolution reaction (HER) process through molecular activation to systematically control surface catalytic activity corresponding to an interfacial charge transfer in a porphyrin monolayer on inactive graphene. The two-dimensional (2D) assembly of porphyrins that create homogeneous active sites (e.g., electronegative tetrapyrroles (N4)) on graphene showed structural stability against electrocatalytic reactions and enhanced charge transfer at the graphene-liquid interface. Performance operations of the graphene field effect transistor (FET) were an effective method to analyse the interfacial charge transfer process associated with information about the chemical nature of the catalytic components. Electronegative pristine porphyrin or Pt-porphyrin networks, where intermolecular hydrogen bonding functioned, showed larger interfacial charge transfers and higher HER performance than Ni-, or Zn-porphyrin. A process to create surface electronegativity by either central N4 or metal (M)-N4 played an important role in the electrocatalytic reaction. These findings will contribute to an in-depth understanding at the molecular level for the synergetic effects of molecular structures on the active sites of electrocatalysts toward HER.

Dual role of Cu2O nanocubes as templates and networking catalysts for hollow and microporous Fe-porphyrin networks.

Cu2O nanocubes were used for the synthesis of hollow and microporous Fe porphyrin networks (H-MFePN). In this synthesis, Cu2O nanocubes performed not only as networking catalysts but also as shape controlling templates. MFePN were formed on the surface of the Cu2O nanocubes through azide-alkyne cycloaddition of tetrakis(4-ethynylphenyl) Fe-porphyrin with 1,4-diazidobenzene. H-MFePN showed excellent catalytic activities in carbene insertion into N-H bonds, maintaining their activities during five recycle tests.

Epitaxial encapsulation of homodispersed CeO2 in a cobalt–porphyrin network derived thin film for the highly efficient oxygen evolution reaction

We have developed a homodispersed CeO2 encapsulated cobalt–porphyrin network derived thin film for the highly efficient oxygen evolution reaction.

Hollow and microporous catalysts bearing Cr(iii)–F porphyrins for room temperature CO2 fixation to cyclic carbonates

Hollow and microporous Cr(iii)–F porphyrin networks showed excellent catalytic activities in room temperature CO2 fixation with epoxides to cyclic carbonates due to the hollow structure and the efficient Lewis acidic activity.

Tailoring Large Pores of Porphyrin Networks on Ag(111) by Metal-Organic Coordination.

The engineering of nanoarchitectures to achieve tailored properties relevant for macroscopic devices is a key motivation of organometallic surface science. To this end, understanding the role of molecular functionalities in structure formation and adatom coordination is of great importance. In this study, the differences in formation of Cu-mediated metal-organic coordination networks based on two pyridyl- and cyano-bearing free-base porphyrins on Ag(111) are elucidated by use of low-temperature scanning tunneling microscopy (STM). Distinct coordination networks evolve via different pathways upon codeposition of Cu adatoms. The cyano-terminated module directly forms 2D porous networks featuring fourfold-coordinated Cu nodes. By contrast, the pyridyl species engage in twofold coordination with Cu and a fully reticulated 2D network featuring a pore size exceeding 3 nm2 only evolves via an intermediate structure based on 1D coordination chains. The STM data and complementary Monte Carlo simulations reveal that these distinct network architectures originate from spatial constraints at the coordination centers. Cu adatoms are also shown to form two- and fourfold monoatomic coordination nodes with monotopic nitrogen-terminated linkers on the very same metal substrate-a versatility that is not achieved by other 3d transition metal centers but consistent with 3D coordination chemistry. This study discloses how specific molecular functionalities can be applied to tailor coordination architectures and highlights the potential of Cu as coordination center in such low-dimensional structures on surfaces.

(Invited) Carbon Nanotube-Templated Synthesis of Covalent Porphyrin Network for Oxygen Reduction Reaction

The fabrication of functional hybrid materials that preserves and combines the properties of their building blocks is a central issue of nanosciences. Among the different classes of nanomaterials, carbon nanotubes are promising for electronics, catalysis and composite applications. Within the context of sustainable development and renewable energy, we and others envisioned the use of functionalized or doped carbon nanotubes in electrocatalytic systems.1 , 2 In such systems, the catalytic sites need to be supported on conducting materials. Carbon nanotubes, thanks to their electrical conductivity and their high surface area appear as the ideal material for that purpose. In actual proton exchange membrane fuel cell devices (PEMFC), the reactions at the electrodes and in particular the reduction of oxygen is performed by platinum nanoparticles. The cost of platinum encourages the development of new catalysts based on non-noble metals. In nature, the reduction of oxygen is performed by iron porphyrins in the active center of enzymes. Thus bio-inspired catalysts based on cobalt or iron macrocycles have been extensively studied for oxygen reduction reaction (ORR).3 , 4 Here, we describe the formation of a covalent network of porphyrins around MWNTs. Our approach is based on adsorption of ethynylporphyrins followed by the dimerization of the triple bonds. The nanotube acts as a template for the formation of the polymeric layer. The nanotube hybrids were characterized and tested for the ORR in a series of electrochemical measurements in acidic conditions. Compared to similar systems in which monomeric porphyrins are simply physisorbed, the nanotube hybrib showed a higher activity, a higher current density, a lower overpotential and a four electrons reaction pathway.5 References (1) Zhang, W.; Sherrell, P.; Minett, A. I.; Razal, J. M.; Chen, J. Energy Environ. Sci. 2010, 3, 1286-1293. (2) Morozan, A.; Jousselme, B.; Palacin, S. Energy Environ. Sci. 2011, 4, 1238-1254. (3) Zagal, J. H.; Griveau, S.; Silva, J. F.; Nyokong, T.; Bedioui, F. Coord. Chem. Rev. 2010, 254, 2755-2791. (4) Morozan, A.; Campidelli, S.; Filoramo, A.; Jousselme, B.; Palacin, S. Carbon 2011, 49, 4839-4847. (5) Hijazi, I.; Bourgeteau, T.; Cornut, R.; Morozan, A.; Filoramo, A.; Leroy, J.; Derycke, V.; Jousselme, B.; Campidelli, S. J. Am. Chem. Soc. 2014, 136, 6348-6354. Figure 1

Porphyrin-based mixed-valent Ag(i)/Ag(ii) and Cu(i)/Cu(ii) networks as efficient heterogeneous catalysts for the azide-alkyne "click" reaction and promising oxidation of ethylbenzene.

By using a new porphyrin-based linker, two unusual mixed-valent Ag(i,ii)- and Cu(i,ii)-organic networks were synthesized. Most strikingly, 1 and 2 exhibit highly efficient catalytic activities for the azide-alkyne "click" reaction and oxidation of ethylbenzene.