Application of μ-Nitrido- and μ-Carbido-Bridged Iron Phthalocyanine Dimers as Cathode-Active Materials for Rechargeable Batteries

Tuning Metal-Phthalocyanine 2D Covalent Organic Frameworks for the Nitrogen Reduction Reaction: Cooperativity of Transition Metals and Organic Linkers

Two-dimensional covalent organic frameworks (2D-COFs) exhibit high activity in the electrochemical nitrogen reduction reaction (NRR), while the structure-performance relationship toward which remains an unsolved problem, therefore hindering the development of efficient catalysts. In this work, a total of 145 candidate transition metal phthalocyanine (TMPc-DX) materials comprised of 29 transition metals and X-phthalocyanine (X = N, O, F, S, and Cl) are evaluated for their capabilities in the NRR by density functional theory calculations. Our computations showed that metal atoms in TMPc-DN/DF/DCl materials could efficiently activate N2 molecules by doping with electron-withdrawing groups. The catalysts MoPc-DN and NbPc-DN are recognized to exhibit the highest electrocatalytic performance for the NRR with the lowest limit potentials of 0.31 and 0.32 V, respectively. Moreover, NbPc-DN showed a significant advantage by suppressing the hydrogen evolution reaction, making it a top contender among TMPc-DX materials for the electrocatalytic NRR. Through detailed orbital interaction analysis, our research has demonstrated that embedding transition metals into the substrate (Pc-DX) results in a direct correlation between the number of electrons transferred to the substrate and the reduction of energy splitting of the metal's d orbital, which directly causes a decrease in the metal's magnetic moment. Consequently, the affinity of the metal for N2 adsorption is directly proportional to the extent of the electron transfer. Our findings underscore the significance of the material's magnetic moment as a preliminary indicator for gauging the effectiveness of N2 adsorption.

Hierarchical Nanostructures of Iron Phthalocyanine Nanowires Coated on Nickel Foam as Catalysts for the Oxygen Evolution Reaction

In this paper, iron phthalocyanine nanowires on a nickel foam (FePc@NF) composite catalyst were prepared by a facile solvothermal approach. The catalyst showed good electrochemical oxygen evolution performance. In 1.0 M KOH electrolyte, 289 mV low overpotential and 49.9 mV dec-1 Tafel slope were seen at a current density of 10 mA cm-2. The excellent electrochemical performance comes from the homogeneous dispersion of phthalocyanine nanostructures on the surface of the nickel foam, which avoids the common agglomeration problem of such catalysts and provides a large number of active sites for the OER reaction, thus improving the catalytic performance of the system.

Porous crystalline conjugated macrocyclic materials and their energy storage applications

Porous crystalline conjugated macrocyclic materials (CMMs) possess high porosity, tunable structure/function and efficient charge transport ability owing to their planar macrocyclic conjugated π-electron system, which make them promising candidates for applications in energy storage. In this review, we thoroughly summarize the timely development of porous crystalline CMMs in energy storage related fields. Specifically, we summarize and discuss their structures and properties. In addition, their energy storage applications, such as lithium ion batteries, lithium sulfur batteries, sodium ion batteries, potassium ion batteries, Li-CO2 batteries, Li-O2 batteries, Zn-air batteries, supercapacitors and triboelectric nanogenerators, are also discussed. Finally, we present the existing challenges and future prospects. We hope this review will inspire the development of advanced energy storage materials based on porous crystalline CMMs.

Effect of porphyrin ligands on the catalytic CH4 oxidation activity of monocationic μ-nitrido-bridged iron porphyrinoid dimers by using H2O2 as an oxidant

The μ-nitrido-bridged iron phthalocyanine homodimer is a potent molecule-based CH4 oxidation catalyst that can effectively oxidize chemically stable CH4 under mild reaction conditions in an acidic aqueous solution including an oxidant such as H2O2. The reactive intermediate is a high-valent iron-oxo species generated upon reaction with H2O2. However, a detailed comparison of the CH4 oxidation activity of the μ-nitrido-bridged iron phthalocyanine dimer with those of μ-nitrido-bridged iron porphyrinoid dimers containing one or two porphyrin ring(s) has not been yet reported, although porphyrins are the most important class of porphyrinoids. Herein, we compare the catalytic CH4 and CH3CH3 oxidation activities of a monocationic μ-nitrido-bridged iron porphyrin homodimer and a monocationic μ-nitrido-bridged heterodimer of an iron porphyrin and an iron phthalocyanine with those of a monocationic μ-nitrido-bridged iron phthalocyanine homodimer in an acidic aqueous solution containing H2O2 as an oxidant. It was demonstrated that the CH4 oxidation activities of monocationic μ-nitrido-bridged iron porphyrinoid dimers containing porphyrin ring(s) were much lower than that of a monocationic μ-nitrido-bridged iron phthalocyanine homodimer. These findings suggested that the difference in the electronic structure of the porphyrinoid rings of monocationic μ-nitrido-bridged iron porphyrinoid dimers strongly affected their catalytic light alkane oxidation activities.

Iron (II) phthalocyanine loaded tourmaline efficiently activates PMS to degrade pharmaceutical contaminants under solar light

Iron (II) phthalocyanine (FePc) is loaded on the surface of the tourmaline (TM) by the reflow method to obtain FePc/TM. This research effectively prevents the π-π stacking of FePc, increased the effective utilization rate of PMS activation under solar light, and further improved the catalytic performance of the catalytic system. The catalytic oxidation efficiency of FePc/TM on carbamazepine (CBZ) and sulfadiazine (SD) can reach 99% under solar light for 15 and 5 min, the total organic carbon (TOC) removal rate can reach 58% and 69% under solar light for 120 min. After 6 cycles, the CBZ removal rate remained above 95%. In addition, the FePc/TM catalytic system has an excellent removal rate for other pharmaceuticals. The results of spin-trapped electron paramagnetic resonance and classical quenching experiments show that FePc/TM can effectively activate PMS to generate active species under solar light, including superoxide radical (•O2-), singlet oxygen (1O2), hydroxyl radicals(•OH), and sulphate radicals (SO4•-). The intermediates of CBZ were identified by Ultra-high performance liquid chromatography and high resolution mass spectrometry, and the degradation pathway was proposed. As the reaction progresses, all CBZ and intermediates are reduced and converted into small acids, or mineralized to H2O, CO2. This work provides an alternative method for the design of efficient activation of PMS activation catalysts under solar light to eliminate residual pharmaceuticals in actual water bodies.

Stacking of a Cofacially Stacked Iron Phthalocyanine Dimer on Graphite Achieved High Catalytic CH4 Oxidation Activity Comparable to That of pMMO

Numerous biomimetic molecular catalysts inspired by methane monooxygenases (MMOs) that utilize iron or copper-oxo species as key intermediates have been developed. However, the catalytic methane oxidation activities of biomimetic molecule-based catalysts are still much lower than those of MMOs. Herein, we report that the close stacking of a μ-nitrido-bridged iron phthalocyanine dimer onto a graphite surface is effective in achieving high catalytic methane oxidation activity. The activity is almost 50 times higher than that of other potent molecule-based methane oxidation catalysts and comparable to those of certain MMOs, in an aqueous solution containing H₂O₂. It was demonstrated that the graphite-supported μ-nitrido-bridged iron phthalocyanine dimer oxidized methane, even at room temperature. Electrochemical investigation and density functional theory calculations suggested that the stacking of the catalyst onto graphite induced partial charge transfer from the reactive oxo species of the μ-nitrido-bridged iron phthalocyanine dimer and significantly lowered the singly occupied molecular orbital level, thereby facilitating electron transfer from methane to the catalyst in the proton-coupled electron-transfer process. The cofacially stacked structure is advantageous for stable adhesion of the catalyst molecule on the graphite surface in the oxidative reaction condition and for preventing decreases in the oxo-basicity and generation rate of the terminal iron-oxo species. We also demonstrated that the graphite-supported catalyst exhibited appreciably enhanced activity under photoirradiation owing to the photothermal effect.

Ultra-High-Capacity Lithium Metal Batteries Based on Multi-Electron Redox Reaction of Organopolysulfides including Conductive Organic Moieties

Recently, organic polysulfides have been synthesized as cathode active materials exceeding the battery performance of sulfur. However, the conventional organic polysulfides have exhibited capacities lower than the theoretical capacity of sulfur because the π-organic moieties do not conjugate with the sulfur chains. In this work, the organopolysulfides, synthesized via inverse vulcanization using disulfide compounds, exhibited higher capacities equal to the theoretical capacity of sulfur because of enhanced electronic conductivity based on the conjugation between organic moieties and sulfur chains. Furthermore, the organopolysulfide including 1,3-dhitiol-2-thione moiety exhibited the highest capacity because of the enhanced electronic conductivity. This finding will pave the way to develop next-generation rechargeable batteries.

Synthesis of a monocationic μ-nitrido-bridged iron porphycene dimer and its methane oxidation activity

Herein, we report the synthesis of a monocationic μ-nitrido-bridged iron porphycene dimer, a structural analogue of a monocationic μ-nitrido-bridged iron phthalocyanine dimer, which is known to be one of the most potent molecule-based catalysts for methane oxidation. ¹H-NMR and single-crystal X-ray structural analyses showed that the porphycene complex includes two Fe(IV) ions, and the structure around the Fe-NFe core is quite similar to that of the monocationic μ-nitrido-bridged iron phthalocyanine dimer. Although methane was oxidized into MeOH, HCHO, and HCOOH in the presence of a silica-supported catalyst of this monocationic μ-nitrido-bridged iron porphycene dimer in an acidic aqueous solution containing excess H₂O₂, its reactive intermediate was not a high-valence iron-oxo species, as in the case of a monocationic μ-nitrido-bridged iron phthalocyanine dimer, but ˙OH. It is suggested that the high-valent iron-oxo species of the μ-nitrido-bridged iron porphycene dimer was gradually decomposed under these reaction conditions, and the decomposed compound catalyzed a Fenton-type reaction. This result indicates that the stability of the oxo-species is indispensable for achieving high catalytic methane oxidation activity using a μ-nitrido-bridged iron porphyrinoid dimer with an Fe-NFe core as a catalyst.

Transition Metal Carbide Complexes

Carbide complexes remain a rare class of molecules. Their paucity does not reflect exceptional instability but is rather due to the generally narrow scope of synthetic procedures for constructing carbide complexes. The preparation of carbide complexes typically revolves around generating L_nM-CE_x fragments, followed by cleavage of the C-E bonds of the coordinated carbon-based ligands (the alternative being direct C atom transfer). Prime examples involve deoxygenation of carbonyl ligands and deprotonation of methyl ligands, but several other p-block fragments can be cleaved off to afford carbide ligands. This Review outlines synthetic strategies toward terminal carbide complexes, bridging carbide complexes, as well as carbide-carbonyl cluster complexes. It then surveys the reactivity of carbide complexes, covering stoichiometric reactions where the carbide ligands act as C₁ reagents, engage in cross-coupling reactions, and enact Fischer-Tropsch-like chemistry; in addition, we discuss carbide complexes in the context of catalysis. Finally, we examine spectroscopic features of carbide complexes, which helps to establish the presence of the carbide functionality and address its electronic structure.