Two-Dimensional Metal–Organic Framework Nanosheets with Cobalt-Porphyrins for High-Performance CO2 Electroreduction

The electrochemical reduction of CO₂ presents a promising strategy to mitigate the greenhouse effect and reduce excess carbon dioxide emission to realize a carbon-neutral energy cycle, but it suffers from the lack of high-performance electrocatalysts. In this work, catalytic active cobalt porphyrin [TCPP(Co)=(5,10,15,20)-tetrakis(4-carboxyphenyl)porphyrin-Co^II] was precisely anchored onto water-stable 2D metal–organic framework (MOF) nanosheets (Zr-BTB) to obtain ultrathin 2D MOF nanosheets [TCPP(Co)/Zr-BTB] with accessible catalytic sites for the CO₂ reduction reaction. Compared with molecular cobalt porphyrin, the TCPP(Co)/Zr-BTB exhibits an ultrahigh turnover frequency (TOF=4768 h⁻¹ at −0.919 V vs. reversible hydrogen electrode, RHE) owing to high active-site utilization. In addition, three post-modified 2D MOF nanosheets [TCPP(Co)/Zr-BTB-PABA, TCPP(Co)/Zr-BTB-PSBA, TCPP(Co)/Zr-BTB-PSABA] were obtained, with the modifiers of p-(aminomethyl)benzoic acid (PABA), p-sulfobenzoic acid potassium (PSBA), and p-sulfamidobenzoic acid (PSABA), to change the micro-environments around TCPP(Co) through the tuning of steric effects. Among them, the TCPP(Co)/Zr-BTB-PSABA exhibited the best performance with a faradaic efficiency (FE_CO) of 85.1 %, TOF of 5315 h⁻¹, and j_total of 6 mA cm⁻² at −0.769 V (vs. RHE). In addition, the long-term durability of the electrocatalysts is evaluated and the role of pH buffer is revealed.     

Recent Advances in Metal–Organic Frameworks for Photo-/Electrocatalytic CO2 Reduction

Considerable attention has been paid to the utilization of CO₂, an abundant carbon source in nature. In this regard, porous catalysts have been eagerly explored with excellent performance for photo-/electrocatalytic reduction of CO₂ to high valued products. Metal–organic frameworks (MOFs), featuring large surface area, high porosity, tunable composition and unique structural characteristics, have been widely exploited in catalytic CO₂ reduction. This Minireview first reports the current progress of MOFs in CO₂ reduction. Then, a specific interest is focused on MOFs in photo-/electrocatalytic reduction of CO₂ by modifying their metal centers, organic linkers, and pores. Finally, the future directions of study are also highlighted to satisfy the requirement of practical applications.     

Single Atom Bi Decorated Copper Alloy Enables C−C Coupling for Electrocatalytic Reduction of CO2 into C2+ Products**

Single atom alloy (SAA) catalysts have been recently explored for promotion of various heterogeneous catalysis, but it remains unexplored for selective electrocatalytic reduction of carbon dioxide (CO₂) into multi-carbon (C₂₊) products involving C−C coupling. Herein we report a single-atomic Bi decorated Cu alloy (denoted as BiCu-SAA) electrocatalyst that could effectively modulate selectivity of CO₂ reduction into C₂₊ products instead of previous C₁ ones. The BiCu-SAA catalyst exhibits remarkably superior selectivity of C₂₊ products with optimal Faradaic efficiency (FE) of 73.4 % compared to the pure copper nanoparticle or Bi nanoparticles-decorated Cu nanocomposites, and its structure and performance can be well maintained at current density of 400 mA cm⁻² under the flow cell system. Based on our in situ characterizations and density functional theory calculations, the BiCu-SAA is found to favor the activation of CO₂ and subsequent C−C coupling during the electrocatalytic reaction, as should be responsible for its extraordinary C₂₊ selectivity.     

Formation of Hierarchical FeCoS2–CoS2 Double-Shelled Nanotubes with Enhanced Performance for Photocatalytic Reduction of CO2

Hierarchical FeCoS₂–CoS₂ double-shelled nanotubes have been rationally designed and constructed for efficient photocatalytic CO₂ reduction under visible light. The synthetic strategy, engaging the two-step cation-exchange reactions, precisely integrates two metal sulfides into a double-shelled tubular heterostructure with both of the shells assembled from ultrathin two-dimensional (2D) nanosheets. Benefiting from the distinctive structure and composition, the FeCoS₂–CoS₂ hybrid can reduce bulk-to-surface diffusion length of photoexcited charge carriers to facilitate their separation. Furthermore, this hybrid structure can expose abundant active sites for enhancing CO₂ adsorption and surface-dependent redox reactions, and harvest incident solar irradiation more efficiently by light scattering in the complex interior. As a result, these hierarchical FeCoS₂–CoS₂ double-shelled nanotubes exhibit superior activity and high stability for photosensitized deoxygenative CO₂ reduction, affording a high CO-generating rate of 28.1 μmol h⁻¹ (per 0.5 mg of catalyst).     

Pre-intercalation of Ammonium Ions in Layered δ-MnO2 Nanosheets for High-Performance Aqueous Zinc-Ion Batteries

Layered manganese dioxide is a promising cathode candidate for aqueous Zn-ion batteries. However, the narrow interlayer spacing, inferior intrinsic electronic conductivity and poor structural stability still limit its practical application. Herein, we report a two-step strategy to incorporate ammonium ions into manganese dioxide (named as AMO) nanosheets as a cathode for boosted Zn ion storage. K⁺-intercalated δ-MnO₂ nanosheets (KMO) grown on carbon cloth are chosen as the self-involved precursor. Of note, ammonium ions could replace K⁺ ions via a facile hydrothermal reaction to enlarge the lattice space and form hydrogen-bond networks. Compared with KMO, the structural stability and the ion transfer kinetics of the layered AMO are enhanced. As expected, the obtained AMO cathode exhibits remarkable electrochemical properties in terms of high reversible capacity, decent rate performance and superior cycling stability over 10000 cycles.     

Layered β-ZrNBr Nitro-Halide as Multifunctional Photocatalyst for Water Splitting and CO2 Reduction

Developing mixed-anion semiconductors for solar fuel production has inspired extensive interest, but the nitrohalide-based photocatalyst is still in shortage. Here we report a layered nitro-halide β-ZrNBr with a narrow band gap of ca. 2.3 eV and low defect density to exhibit multifunctionalities for photocatalytic water reduction, water oxidation and CO₂ reduction under visible-light irradiation. As confirmed by the results of electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations, the formation of anion vacancies in the nitro-halide photocatalyst was inhibited due to its relatively high formation energy. Furthermore, performance of β-ZrNBr can be effectively promoted by a simple exfoliation into nanosheets to shorten the carrier transfer distance as well as to promote charge separation. Our work extends the territory of functional photocatalysts into the nitro-halide, which opens a new avenue for fabricating efficient artificial photosynthesis.     

Fabrication of Multilayer Film Electrode Containing 12-Tungstosilicate Anions and Its Electrocatalytic Reduction for Dioxygen

InthelaStfewyears,moreandmoreinthestshavebeenpaidtoheteroP0lyandisop0lyoxometallates-m0difiedelectrode,owingtotheirexcellenthennal,redoxstabilityandSPedalelectrocatalyticpropenies.Ingeneral,therearethreemainmethodsformothegunsmpeofsPeciesonelectr0desurface,includingelectrocheInicaldep0siti0n,adsorphonandinnnobilhaonofheeroPolyandisopolyoxometallateedonsasadopaninaconduCtinp0lpoermatrix.Recently,G.Decherandco-worerdevelopedthefabricationofmultilayerultrathinfilInsbyaltematindePosition0fbipo…     

Hard-Sphere Random Close-Packed Au47Cd2(TBBT)31 Nanoclusters with a Faradaic Efficiency of Up to 96 % for Electrocatalytic CO2 Reduction to CO

Metal nanoclusters have recently attracted considerable attention, not only because of their special size range but also because of their well-defined compositions and structures. However, subtly tailoring the compositions and structures of metal nanoclusters for potential applications remains challenging. Now, a two-phase anti-galvanic reduction (AGR) method is presented for precisely tailoring Au₄₄(TBBT)₂₈ to produce Au₄₇Cd₂(TBBT)₃₁ nanoclusters with a hard-sphere random close-packed structure, exhibiting Faradaic efficiencies of up to 96 % at −0.57 V for the electrocatalytic reduction of CO₂ to CO.     

Exfoliation of Metal–Organic Frameworks to Give 2D MOF Nanosheets for the Electrocatalytic Oxygen Evolution Reaction

The structure and properties of materials are determined by a diverse range of chemical bond formation and breaking mechanisms, which greatly motivates the development of selectively controlling the chemical bonds in order to achieve materials with specific characteristics. Here, an orientational intervening bond-breaking strategy is demonstrated for synthesizing ultrathin metal–organic framework (MOF) nanosheets through balancing the process of thermal decomposition and liquid nitrogen exfoliation. In such approach, proper thermal treatment can weaken the interlayer bond while maintaining the stability of the intralayer bond in the layered MOFs. And the following liquid nitrogen treatment results in significant deformation and stress in the layered MOFs’ structure due to the instant temperature drop and drastic expansion of liquid N₂, leading to the curling, detachment, and separation of the MOF layers. The produced MOF nanosheets with five cycles of treatment are primarily composed of nanosheets that are less than 10 nm in thickness. The MOF nanosheets exhibit enhanced catalytic performance in oxygen evolution reactions owing to the ultrathin thickness without capping agents which provide improved charge transfer efficiency and dense exposed active sites. This strategy underscores the significance of orientational intervention in chemical bonds to engineer innovative materials.     

Mo–V Keggin Structure Compound and Its Electrocatalytic Reduction Toward Bromate

Abstract  

In this paper, the Mo–V Keggin compound 1, KNa₆[VMo₁₂O₄₀]₂(OH)(H₂O)₃₆, had obtained. Single crystal X-ray analysis revealed that there is the nanometer-sized water cube, Na₆(KOH)(H₂O)₃₆, in [VMo₁₂O₄₀]³⁻ Keggin structure. The Na₆(KOH)(H₂O)₃₆ forms one cuboid house with long side of 22.456 ? and short side of 11.228 ?. The cation water cube acts as a “host” and the globular anion [VMo₁₂O₄₀]³⁻ as “guest” which was captured. The cycle voltammetry study showed that above compound had excellent electrocatalytic activity toward the reduction of bromate. Thermogravimetric analysis was in agreement with the crystal data.     

Preparation of Nano-crystalline Tungsten Carbide Thin Film by Magnetron Sputtering and Their Electrocatalytic Property for PNP Reduction

Nano-crystalline tungsten carbide thin films were deposited on Ni substrates by magnetron sputtering using WC as target material. The crystal structure and morphology of the thin films were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM） Electrochemical investigations showed that the electrode of the thin film exhibited higher electrocatalytic activity in the reaction of p-nitrophenol （PNP） reduction. FT-IR analysis indicated that p-aminophenol （PAP） was synthesized after two step reduction of PNP on nano-crystalline tungsten carbide thin film electrode.     

Electron-Donors–Acceptors Interaction Enhancing Electrocatalytic Activity of Metal-Organic Polymers for Oxygen Reduction

Catalysts with metal-N_x sites have long been considered as effective electrocatalysts for oxygen reduction reaction (ORR), yet the accurate structure-property correlations of these active sites remain debatable. Report here is a proof-of-concept method to construct 1,4,8,11-tetraaza[14]annulene (TAA)-based polymer nanocomposites with well-managed electronic microenvironment via electron-donors/acceptors interaction of altering electron-withdrawing β-site substituents. DFT calculation proves the optimal −Cl substituted catalyst (CoTAA−Cl@GR) tailored the key OH* intermediate interaction with Co−N₄ sites under the d-orbital regulation, hence reaching the top of ORR performance with excellent turnover frequency (0.49 e s⁻¹ site⁻¹). The combination of in situ scanning electrochemical microscopy and variable-frequency square wave voltammetry techniques contribute the great ORR kinetics of CoTAA−Cl@GR to the relatively high accessible site density (7.71×10¹⁹ site g⁻¹) and fast electron outbound propagation mechanism. This work provides theoretical guidance for rational design of high-performance catalysts for ORR and beyond.     

Covalent Organic Framework Materials for Photo/ Electrocatalytic Carbon Dioxide Reduction北大核心CSCD

Covalent organic frameworks （COFs）are a class of emerging materials connected by covalent bonds,which have high thermal/chemical stability （except boric acid COFs）,permanent porosity,large specific surface area and good crystallinity. In addition,the structure of the monomer unit in COFs is adjustable and can coordinate with many transition metal ions to provide catalytic active sites. These advantages make COFs helpful to catalyze various reactions. Among them,COFs have an excellent catalytic effect on the CO2 reduction reaction（CO2 RR）. This is mainly because the adjustable pore structure of COFs allows them to adsorb a large amount of CO2 and the π-π stacking structure in COFs can promote charge transfer, which can greatly improve the efficiency of CO2 reduction. COFs can be used as photo/ electrocatalysts to efficiently reduce CO2 to CO,CH4 ,HCOOH and other products. This review discusses the important achievements of CO2 RR catalyzed by COFs, including photo/electrocatalytic CO2 RR and photoelectric coupling CO2 RR. In addition,the future development of COFs as CO2 RR catalysts is also prospected. © 2022, Science Press (China). All rights reserved.     

Construction of Asymmetrical Dual Jahn–Teller Sites for Photocatalytic CO2 Reduction

Photocatalytic CO₂ reduction (PCR) expresses great attraction to convert useless greenhouse gas into valuable chemical feedstock. However, the weak interactions between catalytic sites and PCR intermediates constrains the PCR activity and selectivity. Herein, we proposed a new strategy to match the intermediates due to the maximum orbital overlap of catalytic sites and C₁ intermediates by establishing dual Jahn–Teller (J–T) sites, in which, the strongly asymmetric J–T sites can break the nonpolar CO₂ molecules and self-adapt the different structure of C₁ intermediates. Taking cobalt carbonate hydroxide as an example, the weakly symmetric dual cobalt (Co₂) dual J–T sites, weakly asymmetric Fe&Co sites and strongly asymmetric Cu&Co sites were assembled. After illumination, the interaction between dual J–T sites and the CO₂ molecules enhances J–T distortion, which further modulates the PCR activity and selectivity. As a result, the Cu&Co sites exhibited CO yield of 8137.9 μmol g⁻¹, about 2.3-fold and 4.2-fold higher than that of the Fe&Co and Co₂ sites within 5-hour photoreaction, respectively. In addition, the selectivity achieved as high as 92.62 % than Fe&Co (88.67 %) and Co₂ sites (55.33 %). This work provides a novel design concept for the construction of dual J–T sites to regulate the catalytic activity and selectivity.     

Solar-Powered Organic Semiconductor–Bacteria Biohybrids for CO2 Reduction into Acetic Acid

An organic semiconductor–bacteria biohybrid photosynthetic system is used to efficiently realize CO₂ reduction to produce acetic acid with the non-photosynthetic bacteria Moorella thermoacetica. Perylene diimide derivative (PDI) and poly(fluorene-co-phenylene) (PFP) were coated on the bacteria surface as photosensitizers to form a p-n heterojunction (PFP/PDI) layer, affording higher hole/electron separation efficiency. The π-conjugated semiconductors possess excellent light-harvesting ability and biocompatibility, and the cationic side chains of organic semiconductors could intercalate into cell membranes, ensuring efficient electron transfer to bacteria. Moorella thermoacetica can thus harvest photoexcited electrons from the PFP/PDI heterojunction, driving the Wood–Ljungdahl pathway to synthesize acetic acid from CO₂ under illumination. The efficiency of this organic biohybrid is about 1.6 %, which is comparable to those of reported inorganic biohybrid systems.     

Photo-excited Oxygen Reduction and Oxygen Evolution Reactions Enable a High-Performance Zn–Air Battery

The storage of solar energy in battery systems is pivotal for a sustainable society, which faces many challenges. Herein, a Zn–air battery is constructed with two cathodes of poly(1,4-di(2-thienyl))benzene (PDTB) and TiO₂ grown on carbon papers to sandwich a Zn anode. The PDTB cathode is illuminated in a discharging process, in which photoelectrons are excited into the conduction band of PDTB to promote oxygen reduction reaction (ORR) and raise the output voltage. In a reverse process, holes in the valence band of the illuminated TiO₂ cathode are driven for the oxygen evolution reaction (OER) by an applied voltage. A record-high discharge voltage of 1.90 V and an unprecedented low charge voltage of 0.59 V are achieved in the photo-involved Zn–air battery, regardless of the equilibrium voltage. This work offers an innovative pathway for photo-energy utilization in rechargeable batteries.     

AuPt Bipyramid Nanoframes as Multifunctional Platforms for In Situ Monitoring of the Reduction of Nitrobenzene and Enhanced Electrocatalytic Methanol Oxidation

Multifunctional metal nanostructures with a hollow feature, especially for nanoframes, are highly attractive owing to their high surface-to-volume ratios. However, pre-grown metal nanocrystals are always involved during the preparation procedure, and a synthetic strategy without the use of a pre-grown template is still a challenge. In this article, a template-free strategy is reported for the preparation of novel AuPt alloy nanoframes through simply mixing HAuCl₄ and H₂PtCl₆ under mild conditions. The alloy nanostructures show a bipyramid-frame hollow architecture with the existence of only the ten ridges and absence of their side faces. This is the first report of bipyramid-like nanoframes and a template-free method under mild conditions. This configuration merges the plasmonic features of Au and highly active catalytic sites of Pt in a single nanostructure, making it an ideal multifunctional platform for catalyzing and monitoring the catalytic reaction in real time. The superior catalytic activity is demonstrated by using the reduction of nitrobenzene to the corresponding aminobenzene as a model reaction. More importantly, the AuPt nanoframes can track the reduction process on the basis of the SERS signals of the reactants, intermediates, and products, which helps to reveal the reaction mechanism. In addition, the AuPt nanoframes show much higher electrocatalytic properties toward the methanol oxidation reaction than commercial Pt/C electrocatalysts.     

Synthesis, Characterization of Heterodinuclear Co-Cu Complex and Its Electrocatalytic Activity towards O_2 Reduction: Implications for Cytochrome c Oxidase Active Site Modeling

IntroductionMetalloenzymesplaymanyimportantrolesinnatureespeciallyinelectron transferbiologicalprocesses .Be causeoftheirimportanceandcomplexity ,manysimplifiedmodelsystemshavebeenconstructedforthestudyoftheirchemistry .Amongvariouspolymetallicmetalloenzymes ,cytochromecoxidase (CcO)istheoneofthemostspecialinterest.CcO ,theterminalenzymeoftherespiratorychain ,catalyzesthereductionofO2 by 4H+,4e- towaterwith outleakageofanypartiallyreducedintermediateswhicharetoxictocellsuchasH2 O2 .Thefree…     

High-Performance K–CO2 Batteries Based on Metal-Free Carbon Electrocatalysts

Metal–CO₂ batteries have attracted much attention owing to their high energy density and use of greenhouse CO₂ waste as the energy source. However, the increasing cost of lithium and the low discharge potential of Na–CO₂ batteries create obstacles for practical applications of Li/Na–CO₂ batteries. Recently, earth-abundant potassium ions have attracted considerable interest as fast ionic charge carriers for electrochemical energy storage. Herein, we report the first K–CO₂ battery with a carbon-based metal-free electrocatalyst. The battery shows a higher theoretical discharge potential (E^⊖=2.48 V) than that of Na–CO₂ batteries (E^⊖=2.35 V) and can operate for more than 250 cycles (1500 h) with a cutoff capacity of 300 mA h g⁻¹. Combined DFT calculations and experimental observations revealed a reaction mechanism involving the reversible formation and decomposition of P12₁/c1-type K₂CO₃ at the efficient carbon-based catalyst.     

Mechanistic Investigation of Alkali-Treated Photocatalytic CO2 Reduction: The Role of OH− and Metal Cations for Almost 100 % Selectivity of CO

In this work, the modulation of activity and selectivity via photoreduction of carbon dioxide under simulated sunlight was achieved by treating P25 and P25/Pt NPs with KOH. It found that KOH treatment could significantly improve the overall conversion efficiency and switch the selectivity for CO. Photoelectric characterizations and CO₂-TPD demonstrated that the synergistic effect of K⁺ and OH^- accelerated the separation and migration of photogenerated charges, and also improved CO₂ adsorption level. Significantly, the K ions could act as active sites for CO₂ adsorption and further activation. In situ FTIR measurements and DFT calculations confirmed that K⁺ enhanced the charge density of adjacent atoms and stabilize CO* groups, reducing the reaction energy barrier and inducing the switching of original CH₄ to CO, which played a selective regulatory role. This study provides insights into the photocatalytic activity and selectivity of alkali-treated photocatalysts and facilitates the design of efficient and product-specific photocatalysis.