Search

Molecular electrocatalysis requires the immobilization of molecular catalysts on electrode materials for practical uses. Direct adsorption of catalyst molecules on electrode materials is simple, but grafting molecules through chemical bonds can significantly improve electrocatalytic efficiency and durability. However, designing and synthesizing catalyst molecules to simultaneously improve catalytic activities and realize easy grafting on electrodes is challenging. The study herein reports on a one‐pot strategy to graft Co corroles on pyridine‐modified carbon nanotubes (CNTs) for oxygen electrocatalysis. By modifying CNTs with pyridines, the resulting pyridine‐modified CNTs can function as platforms to grab in situ generated Co corroles through the axial pyridine ligation on Co. Such an immobilization strategy combines three effects for the regulation of electrocatalysis, including the axial ligand effect, the electron transfer effect, and the chemical bond effect. The resulting hybrid materials show high efficiency for oxygen electrocatalysis, and the Zn–air battery assembled using these materials displays comparable performance as the Pt/Ir‐based battery. Moreover, the electrocatalytic efficiency of these hybrid materials can be systematically tuned by using different pyridines, highlighting the controllable feature of this strategy. Therefore, this work is significant to present a one‐pot three‐in‐one strategy to immobilize catalyst molecules on CNTs for electrocatalysis. [ABSTRACT FROM AUTHOR]

The effect of proton transfer on water oxidation has hardly been measurably established in heterogeneous electrocatalysts. Herein, two isomorphous manganese phosphates (NH4MnPO4 ⋅ H2O and KMnPO4 ⋅ H2O) were designed to form an ideal platform to study the effect of proton transfer on water oxidation. The hydrogen‐bonding network in NH4MnPO4 ⋅ H2O has been proven to be solely responsible for its better activity. The differences of the proton transfer kinetics in the two materials indicate a fast proton hopping transfer process with a low activation energy in NH4MnPO4 ⋅ H2O. In addition, the hydrogen‐bonding network can effectively promote the proton transfer between adjacent Mn sites and further stabilize the MnIII−OH intermediates. The faster proton transfer results in a higher proportion of zeroth‐order in [H+] for OER. Thus, proton transfer‐affected electrocatalytic water oxidation has been measurably observed to bring detailed insights into the mechanism of water oxidation. [ABSTRACT FROM AUTHOR]

The effect of proton transfer on water oxidation has hardly been measurably established in heterogeneous electrocatalysts. Herein, two isomorphous manganese phosphates (NH4MnPO4 ⋅ H2O and KMnPO4 ⋅ H2O) were designed to form an ideal platform to study the effect of proton transfer on water oxidation. The hydrogen‐bonding network in NH4MnPO4 ⋅ H2O has been proven to be solely responsible for its better activity. The differences of the proton transfer kinetics in the two materials indicate a fast proton hopping transfer process with a low activation energy in NH4MnPO4 ⋅ H2O. In addition, the hydrogen‐bonding network can effectively promote the proton transfer between adjacent Mn sites and further stabilize the MnIII−OH intermediates. The faster proton transfer results in a higher proportion of zeroth‐order in [H+] for OER. Thus, proton transfer‐affected electrocatalytic water oxidation has been measurably observed to bring detailed insights into the mechanism of water oxidation. [ABSTRACT FROM AUTHOR]

In enzymes, the active site residues function differently to promote chemical reactions. Such a role‐specialized division of labor has been rarely realized by synthetic catalysts. We report herein on catalytic CO2 reduction with Fe porphyrins decorated with two cationic N,N,N‐trimethylbenzylamine groups in cis‐ or trans‐arrangement. The cis‐isomer outperforms the trans‐isomer and reaches a TOFmax of 4.4×105 s−1 in acetonitrile using phenol proton source. Theoretical studies revealed that the two cationic units in the cis‐isomer are more effective than a single cationic unit to improve the CO2 binding, and more importantly, they function differently but cooperatively to promote the C−O bond cleavage: one interacts with the CO2‐adduct, while the other one interacts with the phenol molecule through electrostatic interactions. This work therefore presents a significant example of synthetic catalysts, which boost chemical reactions using a role‐specialized strategy for substrate activation. [ABSTRACT FROM AUTHOR]

In enzymes, the active site residues function differently to promote chemical reactions. Such a role‐specialized division of labor has been rarely realized by synthetic catalysts. We report herein on catalytic CO2 reduction with Fe porphyrins decorated with two cationic N,N,N‐trimethylbenzylamine groups in cis‐ or trans‐arrangement. The cis‐isomer outperforms the trans‐isomer and reaches a TOFmax of 4.4×105 s−1 in acetonitrile using phenol proton source. Theoretical studies revealed that the two cationic units in the cis‐isomer are more effective than a single cationic unit to improve the CO2 binding, and more importantly, they function differently but cooperatively to promote the C−O bond cleavage: one interacts with the CO2‐adduct, while the other one interacts with the phenol molecule through electrostatic interactions. This work therefore presents a significant example of synthetic catalysts, which boost chemical reactions using a role‐specialized strategy for substrate activation. [ABSTRACT FROM AUTHOR]

Proton transfer is vital for many biological and chemical reactions. Hydrogen‐bonded water‐containing networks are often found in enzymes to assist proton transfer, but similar strategy has been rarely presented by synthetic catalysts. We herein report the Co corrole 1 with an appended crown ether unit and its boosted activity for the hydrogen evolution reaction (HER). Crystallographic and 1H NMR studies proved that the crown ether of 1 can grab water via hydrogen bonds. By using protic acids as proton sources, the HER activity of 1 was largely boosted with added water, while the activity of crown‐ether‐free analogues showed very small enhancement. Inhibition studies by adding 1) external 18‐crown‐6‐ether to extract water molecules and 2) potassium ion or N‐benzyl‐n‐butylamine to block the crown ether of 1 further confirmed its critical role in assisting proton transfer via grabbed water molecules. This work presents a synthetic example to boost HER through water‐containing networks. [ABSTRACT FROM AUTHOR]

Proton transfer is vital for many biological and chemical reactions. Hydrogen‐bonded water‐containing networks are often found in enzymes to assist proton transfer, but similar strategy has been rarely presented by synthetic catalysts. We herein report the Co corrole 1 with an appended crown ether unit and its boosted activity for the hydrogen evolution reaction (HER). Crystallographic and 1H NMR studies proved that the crown ether of 1 can grab water via hydrogen bonds. By using protic acids as proton sources, the HER activity of 1 was largely boosted with added water, while the activity of crown‐ether‐free analogues showed very small enhancement. Inhibition studies by adding 1) external 18‐crown‐6‐ether to extract water molecules and 2) potassium ion or N‐benzyl‐n‐butylamine to block the crown ether of 1 further confirmed its critical role in assisting proton transfer via grabbed water molecules. This work presents a synthetic example to boost HER through water‐containing networks. [ABSTRACT FROM AUTHOR]

Achieving a selective 2 e− or 4 e− oxygen reduction reaction (ORR) is critical but challenging. Herein, we report controlling ORR selectivity of Co porphyrins by tuning only steric effects. We designed Co porphyrin 1 with meso‐phenyls each bearing a bulky ortho‐amido group. Due to the resulted steric hinderance, 1 has four atropisomers with similar electronic structures but dissimilar steric effects. Isomers αβαβ and αααα catalyze ORR with n=2.10 and 3.75 (n is the electron number transferred per O2), respectively, but ααββ and αααβ show poor selectivity with n=2.89–3.10. Isomer αβαβ catalyzes 2 e− ORR by preventing a bimolecular O2 activation path, while αααα improves 4 e− ORR selectivity by improving O2 binding at its pocket, a feature confirmed by spectroscopy methods, including O K‐edge near‐edge X‐ray absorption fine structure. This work represents an unparalleled example to improve 2 e− and 4 e− ORR by tuning only steric effects without changing molecular and electronic structures. [ABSTRACT FROM AUTHOR]

Achieving a selective 2 e− or 4 e− oxygen reduction reaction (ORR) is critical but challenging. Herein, we report controlling ORR selectivity of Co porphyrins by tuning only steric effects. We designed Co porphyrin 1 with meso‐phenyls each bearing a bulky ortho‐amido group. Due to the resulted steric hinderance, 1 has four atropisomers with similar electronic structures but dissimilar steric effects. Isomers αβαβ and αααα catalyze ORR with n=2.10 and 3.75 (n is the electron number transferred per O2), respectively, but ααββ and αααβ show poor selectivity with n=2.89–3.10. Isomer αβαβ catalyzes 2 e− ORR by preventing a bimolecular O2 activation path, while αααα improves 4 e− ORR selectivity by improving O2 binding at its pocket, a feature confirmed by spectroscopy methods, including O K‐edge near‐edge X‐ray absorption fine structure. This work represents an unparalleled example to improve 2 e− and 4 e− ORR by tuning only steric effects without changing molecular and electronic structures. [ABSTRACT FROM AUTHOR]

Iron porphyrin 1 with appending phenolic group was synthesized and examined as electrocatalyst for the carbon dioxide reduction (CO2RR). Unexpectedly, the chloride salt 1‐Cl is much less active as compared to iron porphyrin 2‐Cl, the structural analogue lacking the hanging phenolic group. By using the triflate salts, 1‐OTf is three times more active than 1‐Cl, while 2‐OTf displays the same activity as 2‐Cl for CO2RR. The observed trend 1‐OTf>2‐OTf=2‐Cl>1‐Cl indicates that the phenolic group has both positive effect as local proton donating site and unexpected negative effect on electrocatalytic CO2RR. [ABSTRACT FROM AUTHOR]

Electrodes for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are required in energy conversion and storage technologies. An assembly strategy involves covalently grafting Co corrole 1 onto Fe3O4 nanoarrays grown on Ti mesh. The resulted electrode shows significantly improved activity and durability for OER and ORR in neutral media as compared to Fe3O4 alone and with directly adsorbed 1. It also displays higher atom efficiency (at least two magnitudes larger turnover frequency) than reported electrodes. Using this electrode in a neutral Zn‐air battery, a small charge–discharge voltage gap of 1.19 V, large peak power density of 90.4 mW cm−2, and high rechargeable stability for >100 h are achieved, opening a promising avenue of molecular electrocatalysis in a metal–air battery. This work shows a molecule‐engineered electrode for electrocatalysis and demonstrates their potential applications in energy conversion and storage. [ABSTRACT FROM AUTHOR]

Electrodes for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are required in energy conversion and storage technologies. An assembly strategy involves covalently grafting Co corrole 1 onto Fe3O4 nanoarrays grown on Ti mesh. The resulted electrode shows significantly improved activity and durability for OER and ORR in neutral media as compared to Fe3O4 alone and with directly adsorbed 1. It also displays higher atom efficiency (at least two magnitudes larger turnover frequency) than reported electrodes. Using this electrode in a neutral Zn‐air battery, a small charge–discharge voltage gap of 1.19 V, large peak power density of 90.4 mW cm−2, and high rechargeable stability for >100 h are achieved, opening a promising avenue of molecular electrocatalysis in a metal–air battery. This work shows a molecule‐engineered electrode for electrocatalysis and demonstrates their potential applications in energy conversion and storage. [ABSTRACT FROM AUTHOR]

Water splitting is promising to realize a hydrogen‐based society. The practical use of molecular water‐splitting catalysts relies on their integration onto electrode materials. We describe herein the immobilization of cobalt corroles on carbon nanotubes (CNTs) by four strategies and compare the performance of the resulting hybrids for H2 and O2 evolution. Co corroles can be covalently attached to CNTs with short conjugated linkers (the hybrid is denoted as H1) or with long alkane chains (H2), or can be grafted to CNTs via strong π–π interactions (H3) or via simple adsorption (H4). An activity trend H1≫H3>H2≈H4 is obtained for H2 and O2 evolution, showing the critical role of electron transfer ability on electrocatalysis. Notably, H1 is the first Janus catalyst for both H2 and O2 evolution reactions in pH 0–14 aqueous solutions. Therefore, this work is significant to show potential uses of electrode materials with well‐designed molecular catalysts in electrocatalysis. pH range rover: A hybrid material allowing fast electron transfer between cobalt corroles and carbon nanotubes (CNTs) catalyzes the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in pH 0–14 aqueous solutions with high efficiency and stability. This is the first example of bifunctional HER and OER catalysts that work in such wide pH range. [ABSTRACT FROM AUTHOR]

Water splitting is promising to realize a hydrogen‐based society. The practical use of molecular water‐splitting catalysts relies on their integration onto electrode materials. We describe herein the immobilization of cobalt corroles on carbon nanotubes (CNTs) by four strategies and compare the performance of the resulting hybrids for H2 and O2 evolution. Co corroles can be covalently attached to CNTs with short conjugated linkers (the hybrid is denoted as H1) or with long alkane chains (H2), or can be grafted to CNTs via strong π–π interactions (H3) or via simple adsorption (H4). An activity trend H1≫H3>H2≈H4 is obtained for H2 and O2 evolution, showing the critical role of electron transfer ability on electrocatalysis. Notably, H1 is the first Janus catalyst for both H2 and O2 evolution reactions in pH 0–14 aqueous solutions. Therefore, this work is significant to show potential uses of electrode materials with well‐designed molecular catalysts in electrocatalysis. [ABSTRACT FROM AUTHOR]

Selective visible-light-driven O2 reduction to H2O2 was realized using BODIPY photosensitizers (PS) in the presence of ferrocene (Fc) as the reductant and acetic acid as the proton source. Mechanistic studies suggested that O2 could be activated by 3PS* through an energy transfer pathway to give singlet oxygen (1O2) in the absence of Fc. However, with Fc, 3PS* was first reductively quenched to PSṖ−, which was able to reduce O2 to the superoxide radical form in a subsequent electron transfer step. [ABSTRACT FROM AUTHOR]

A newly designed copper complex of 5,15-bis(pentafluorophenyl)-10,20-bis(o-carborane)porphyrin (1) was synthesized and tested for the electrocatalytic hydrogen evolution reaction (HER). In acetonitrile, 1 was much more efficient than Cu 5,15-bis(pentafluorophenyl)-10,20-diphenylporphyrin (2) for electrocatalytic HER by shifting the catalytic wave to the anodic direction by 190 mV. In aqueous media, 1 also outperformed 2 by achieving higher current densities under smaller overpotentials. This enhancement was attributed to the aromatic and the strong electron-withdrawing properties of o-carborane groups. This work is significant to address the crucial effects of meso-(o-carborane) substituents of metal porphyrins on boosting the electrocatalytic HER. [ABSTRACT FROM AUTHOR]

Dermatofi brosarcoma protuberans (DFSP) are rare malignant skin tumor, and scalp DFSP is even lesser than 5% of all DFSP, therefore, being seldom reported. We recently treated two cases of recurrent scalp DFSPs. One was a 38-year-old male, who accept lumpectomy for the fi rst time; however, it recurred 9 months later. We then performed a wide excision resulting in no recurrence in the subsequent 4 years. Another patient was a 26-year-old female, who accept an in situ tumorectomy for the fi rst time, and 2 years later; the recurrent mass became 9 × 9 cm in size. We gave her another operation, but only 3 months later local recurrence appeared. For the both cases, we collected their case histories, intraoperative fi ndings, pathologic detections, and follow-up results, all of which may help the dermatologists to extend knowledge about this rare disease. Moreover, an exhaustive review of the literature is included with emphasis on diagnosis, different diagnosis and treatments. [ABSTRACT FROM AUTHOR]

The established water network can play critical roles in assisting proton transfer, leading to improved electrocatalytic activity for the hydrogen evolution reaction, which mimics water-network-assisted proton transfer as found in metalloproteins. Keywords: Cobalt Corrole; Hydrogen Evolution; Molecular Electrocatalysis; Proton Transfer; Water Network EN Cobalt Corrole Hydrogen Evolution Molecular Electrocatalysis Proton Transfer Water Network 1 1 1 02/17/22 20220221 NES 220221 B A cobalt corrole b with an appended crown ether unit displays significantly boosted electrocatalytic hydrogen evolution activity in the presence of water as reported by Rui Cao and co-workers in their Communication (e202114310). Back Cover: Introducing Water-Network-Assisted Proton Transfer for Boosted Electrocatalytic Hydrogen Evolution with Cobalt Corrole (Angew. [Extracted from the article]

Keywords: Cobalt Corrole; Hydrogen Evolution; Molecular Electrocatalysis; Proton Transfer; Water Network EN Cobalt Corrole Hydrogen Evolution Molecular Electrocatalysis Proton Transfer Water Network 1 1 1 02/18/22 20220221 NES 220221 B Ein Cobalt-Corrol b mit einer Kronenether-Einheit zeigt eine deutlich gesteigerte Aktivität in der elektrokatalytischen Wasserstoffentwicklung in Gegenwart von Wasser, wie Rui Cao et al. in ihrer Zuschrift berichten (e202114310). Rücktitelbild: Introducing Water-Network-Assisted Proton Transfer for Boosted Electrocatalytic Hydrogen Evolution with Cobalt Corrole (Angew. Cobalt Corrole, Hydrogen Evolution, Molecular Electrocatalysis, Proton Transfer, Water Network. [Extracted from the article]

This work represents an unparalleled example of improving the oxygen reduction selectivity by tuning only steric effects of the catalysts without changing molecular and electronic structures. Keywords: atropisomers; molecular electrocatalysis; oxygen reduction; selectivity control; steric effect EN atropisomers molecular electrocatalysis oxygen reduction selectivity control steric effect 13114 13114 1 05/28/21 20210601 NES 210601 B Control of the selectivity b of the oxygen reduction reaction through tuning of molecular steric effects is demonstrated by Ran Long, Rui Cao, and co-workers in their Communication on page 12742. Back Cover: Controlling Oxygen Reduction Selectivity through Steric Effects: Electrocatalytic Two-Electron and Four-Electron Oxygen Reduction with Cobalt Porphyrin Atropisomers (Angew. [Extracted from the article]

Keywords: atropisomers; molecular electrocatalysis; oxygen reduction; selectivity control; steric effect EN atropisomers molecular electrocatalysis oxygen reduction selectivity control steric effect 13224 13224 1 05/28/21 20210601 NES 210601 B Eine Kontrolle der Selektivität b der Sauerstoffreduktionsreaktion durch Abstimmung der molekularen sterischen Effekte wird in der Zuschrift auf S. 12852 von Ran Long, Rui Cao et al. demonstriert. Rücktitelbild: Controlling Oxygen Reduction Selectivity through Steric Effects: Electrocatalytic Two-Electron and Four-Electron Oxygen Reduction with Cobalt Porphyrin Atropisomers (Angew. Atropisomers, molecular electrocatalysis, oxygen reduction, selectivity control, steric effect. [Extracted from the article]

A cobalt porphyrin complex with a pendant imidazole base ([(L1)CoII]) is an efficient catalyst for the homogeneous catalytic two‐electron reduction of dioxygen by 1,1′‐dimethylferrocene (Me2Fc) in the presence of triflic acid (HOTf), as compared with a cobalt porphyrin complex without a pendant imidazole base ([(L2)CoII]). The pendant imidazole ligand plays a crucial role not only to provide an imidazolinium proton for proton‐coupled electron transfer (PCET) from [(L1)CoII] to O2 in the presence of HOTf but also to facilitate electron transfer (ET) from [(L1)CoII] to O2 in the absence of HOTf. The kinetics analysis and the detection of intermediates in the stoichiometric and catalytic reduction of O2 have provided clues to clarify the crucial roles of the pendant imidazole ligand of [(L1)CoII] for the first time. [ABSTRACT FROM AUTHOR]

A cobalt porphyrin complex with a pendant imidazole base ([(L1)CoII]) is an efficient catalyst for the homogeneous catalytic two‐electron reduction of dioxygen by 1,1′‐dimethylferrocene (Me2Fc) in the presence of triflic acid (HOTf), as compared with a cobalt porphyrin complex without a pendant imidazole base ([(L2)CoII]). The pendant imidazole ligand plays a crucial role not only to provide an imidazolinium proton for proton‐coupled electron transfer (PCET) from [(L1)CoII] to O2 in the presence of HOTf but also to facilitate electron transfer (ET) from [(L1)CoII] to O2 in the absence of HOTf. The kinetics analysis and the detection of intermediates in the stoichiometric and catalytic reduction of O2 have provided clues to clarify the crucial roles of the pendant imidazole ligand of [(L1)CoII] for the first time. [ABSTRACT FROM AUTHOR]

In nature, cytochrome c oxidases catalyze the 4e− oxygen reduction reaction (ORR) at the heme/Cu site, in which CuI is used to assist O2 activation. Because of the thermodynamic barrier to generate CuI, synthetic Fe‐porphyrin/Cu complexes usually show moderate electrocatalytic ORR activity. We herein report on a Co‐corrole/Co complex 1‐Co for energy‐efficient electrocatalytic ORR. By hanging a CoII ion over Co corrole, 1‐Co realizes electrocatalytic 4e− ORR with a half‐wave potential of 0.89 V versus RHE, which is outstanding among corrole‐based electrocatalysts. Notably, 1‐Co outperforms Co corrole hanged with CuII or ZnII. We revealed that the hanging CoII ion can provide an electron to improve O2 binding thermodynamically and dynamically, a function represented by the biological CuI ion of the heme/Cu site. This work is significant to present a remarkable ORR electrocatalyst and to show the vital role of a second‐sphere redox‐active metal ion in promoting O2 binding and activation. [ABSTRACT FROM AUTHOR]

In nature, cytochrome c oxidases catalyze the 4e− oxygen reduction reaction (ORR) at the heme/Cu site, in which CuI is used to assist O2 activation. Because of the thermodynamic barrier to generate CuI, synthetic Fe‐porphyrin/Cu complexes usually show moderate electrocatalytic ORR activity. We herein report on a Co‐corrole/Co complex 1‐Co for energy‐efficient electrocatalytic ORR. By hanging a CoII ion over Co corrole, 1‐Co realizes electrocatalytic 4e− ORR with a half‐wave potential of 0.89 V versus RHE, which is outstanding among corrole‐based electrocatalysts. Notably, 1‐Co outperforms Co corrole hanged with CuII or ZnII. We revealed that the hanging CoII ion can provide an electron to improve O2 binding thermodynamically and dynamically, a function represented by the biological CuI ion of the heme/Cu site. This work is significant to present a remarkable ORR electrocatalyst and to show the vital role of a second‐sphere redox‐active metal ion in promoting O2 binding and activation. [ABSTRACT FROM AUTHOR]

Several H−H bond forming pathways have been proposed for the hydrogen evolution reaction (HER). Revealing these HER mechanisms is of fundamental importance for the rational design of catalysts and is also extremely challenging. Now, an unparalleled example of switching between homolytic and heterolytic HER mechanisms is reported. Three nickel(II) porphyrins were designed and synthesized with distinct steric effects by introducing bulky amido moieties to ortho‐ or para‐positions of the meso‐phenyl groups. These porphyrins exhibited different catalytic HER behaviors. For these Ni porphyrins, although their 1e‐reduced forms are active to reduce trifluoroacetic acid, the resulting Ni hydrides (depending on the steric effects of porphyrin rings) have different pathways to make H2. Understanding HER processes, especially controllable switching between homolytic and heterolytic H−H bond formation pathways through molecular engineering, is unprecedented in electrocatalysis. [ABSTRACT FROM AUTHOR]

Several H−H bond forming pathways have been proposed for the hydrogen evolution reaction (HER). Revealing these HER mechanisms is of fundamental importance for the rational design of catalysts and is also extremely challenging. Now, an unparalleled example of switching between homolytic and heterolytic HER mechanisms is reported. Three nickel(II) porphyrins were designed and synthesized with distinct steric effects by introducing bulky amido moieties to ortho‐ or para‐positions of the meso‐phenyl groups. These porphyrins exhibited different catalytic HER behaviors. For these Ni porphyrins, although their 1e‐reduced forms are active to reduce trifluoroacetic acid, the resulting Ni hydrides (depending on the steric effects of porphyrin rings) have different pathways to make H2. Understanding HER processes, especially controllable switching between homolytic and heterolytic H−H bond formation pathways through molecular engineering, is unprecedented in electrocatalysis. [ABSTRACT FROM AUTHOR]

The nucleophilic attack of water or hydroxide on metal‐oxo units forms an O−O bond in the oxygen evolution reaction (OER). Coordination tuning to improve this attack is intriguing but has been rarely realized. We herein report on improved OER catalysis by metal porphyrin 1‐M (M=Co, Fe) with a coordinatively unsaturated metal ion. We designed and synthesized 1‐M by sterically blocking one porphyrin side with a tethered tetraazacyclododecane unit. With this protection, the metal‐oxo species generated in OER can maintain an unoccupied trans axial site. Importantly, 1‐M displays a higher OER activity in alkaline solutions than analogues lacking such an axial protection by decreasing up to 150‐mV overpotential to achieve 10 mA/cm2 current density. Theoretical studies suggest that with an unoccupied trans axial site, the metal‐oxo unit becomes more positively charged and thus is more favoured for the hydroxide nucleophilic attack as compared to metal‐oxo units bearing trans axial ligands. [ABSTRACT FROM AUTHOR]

The nucleophilic attack of water or hydroxide on metal‐oxo units forms an O−O bond in the oxygen evolution reaction (OER). Coordination tuning to improve this attack is intriguing but has been rarely realized. We herein report on improved OER catalysis by metal porphyrin 1‐M (M=Co, Fe) with a coordinatively unsaturated metal ion. We designed and synthesized 1‐M by sterically blocking one porphyrin side with a tethered tetraazacyclododecane unit. With this protection, the metal‐oxo species generated in OER can maintain an unoccupied trans axial site. Importantly, 1‐M displays a higher OER activity in alkaline solutions than analogues lacking such an axial protection by decreasing up to 150‐mV overpotential to achieve 10 mA/cm2 current density. Theoretical studies suggest that with an unoccupied trans axial site, the metal‐oxo unit becomes more positively charged and thus is more favoured for the hydroxide nucleophilic attack as compared to metal‐oxo units bearing trans axial ligands. [ABSTRACT FROM AUTHOR]

Integrating molecular catalysts into designed frameworks often enables improved catalysis. Compared with porphyrin‐based frameworks, metal‐corrole‐based frameworks have been rarely developed, although monomeric metal corroles are usually more efficient than porphyrin counterparts for the electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). We herein report on metal‐corrole‐based porous organic polymers (POPs) as ORR and OER electrocatalysts. M‐POPs (M=Mn, Fe, Co, Cu) were synthesized by coupling metal 10‐phenyl‐5,15‐(4‐iodophenyl)corrole with tetrakis(4‐ethynylphenyl)methane. Compared with metal corrole monomers, M‐POPs displayed significantly enhanced catalytic activity and stability. Co‐POP outperformed other M‐POPs by achieving four‐electron ORR with a half‐wave potential of 0.87 V vs. RHE and reaching 10 mA cm−2 OER current density at 340 mV overpotential. This work is unparalleled to develop and explore metal‐corrole‐based POPs as electrocatalysts. [ABSTRACT FROM AUTHOR]

Integrating molecular catalysts into designed frameworks often enables improved catalysis. Compared with porphyrin‐based frameworks, metal‐corrole‐based frameworks have been rarely developed, although monomeric metal corroles are usually more efficient than porphyrin counterparts for the electrocatalytic oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). We herein report on metal‐corrole‐based porous organic polymers (POPs) as ORR and OER electrocatalysts. M‐POPs (M=Mn, Fe, Co, Cu) were synthesized by coupling metal 10‐phenyl‐5,15‐(4‐iodophenyl)corrole with tetrakis(4‐ethynylphenyl)methane. Compared with metal corrole monomers, M‐POPs displayed significantly enhanced catalytic activity and stability. Co‐POP outperformed other M‐POPs by achieving four‐electron ORR with a half‐wave potential of 0.87 V vs. RHE and reaching 10 mA cm−2 OER current density at 340 mV overpotential. This work is unparalleled to develop and explore metal‐corrole‐based POPs as electrocatalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • 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. [ABSTRACT FROM AUTHOR]