Catalytic Center Research Articles

High‐Throughput Screening of Co‐Fe‐Ni Electrocatalysts for High‐Current‐Density Water Electrolysis

AbstractDeveloping oxygen evolution reaction (OER) catalysts with optimum composition and highly active catalytic centres is a challenge during electrode scale‐up. We show a selection strategy for the optimum composition of Co‐Fe‐Ni catalyst systems through a scanning droplet cell‐based high‐throughput screening on thin‐film materials libraries, followed by fabrication and testing of the selected compositions in the form of catalyst‐coated porous electrodes for the OER in alkaline media. The electrode with optimum composition (Co17Fe25Ni58_Ni foam) exhibits a high current density of 1 A cm−2 during water electrolysis at an operating potential of ∼1.9 V.

Ru0.1Mn0.9Ox Electrocatalyst for Durable Oxygen Evolution in Acid Seawater

AbstractCurrently, direct electrolysis of seawater for green hydrogen production is primarily focused on neutral and alkaline systems. However, the precipitation of calcium and magnesium ions restricts the advancement of this technology. An acidic system can effectively address this issue. Given that Ru/Ir‐based catalysts with high oxygen evolution reaction (OER) activity also exhibit high chlorine evolution reaction (CER) activity, acid seawater splitting requires anodes with higher selectivity and stability compared to the other two systems. In this study, we propose a non‐precious Ru0.1Mn0.9Ox as the active anode for direct acid seawater electrolysis, which exhibits a high OER selectivity and remarkable stability for more than 1200 hours. Different from the Cl−‐free system, *Cl occupied on Ru sites could shift the OER active center to Mn on Ru0.1Mn0.9Ox, which prevents the lattice oxygen consumed on Ru and hinders the metal site dissolution. As the CER‐insensitive catalytic center, Mn activated by the introduction of Ru can adsorb a substantial amount of *OH, creating an OER‐favored local environment that inhibits CER. We introduce Cl−‐assisted transfer of OER active sites to CER‐insensitive Mn as a fundamental strategy for achieving highly selective and durable oxygen evolution in acidic seawater.

Structurally Asymmetric Ni−O−Mn Node in Metal–Organic Layers on Carbon Nitride Support for CO2 Photoreduction

AbstractThe Jahn–Teller (J–T) effect‐induced lattice distortion presents an advantageous approach to tailor the electronic structure and CO2 adsorption properties of catalytic centers, consequently conferring desirable photocatalytic CO2 reduction activity and selectivity. Nevertheless, achieving precise J–T distortion control over catalytic sites to enhance CO2 adsorption/activation and target‐product desorption remains a formidable challenge. In this work, we successfully induced J–T lattice distortion in neighboring Ni sites by exchanging high‐spin Mn2+ into Ni−O−Ni nodes. EXAFS results and DFT simulations revealed that the highly asymmetric Ni−O−Mn nodes induced structural contraction (shortened Ni−O bonds) in the adjacent Ni−O lattice. The magnetic hysteresis loop (M−H) confirmed that the introduction of Mn2+ increased the number of spin electrons, thereby increasing the magnetization intensity. The spin mismatch between photogenerated electrons and holes suppressed charge recombination. Significantly, the d orbitals of the Ni sites in the Ni−O−Mn nodes exhibited strong orbital hybridization with the p orbitals of CO2, as evidenced by the enhanced d‐p orbital overlap, facilitating rapid CO2 adsorption and activation. Consequently, the sample featuring lattice‐mismatched Ni−O−Mn nodes exhibited an 8.79‐fold enhancement in CO production rate compared to the Ni−O−Ni nodes, in the absence of cocatalysts and sacrificial reagents.

Surface reaction mechanism of ZSM-5(3T)@NH2-MIL-53(Al) core-shell catalyst for dimethyldichlorosilane synthesis

Dimethyldichlorosilane is one of the most important basic monomers in the silicone industry. It is also can be recovered through by-products disproportionation reactions during synthesis. This paper investigated the reaction mechanism of ZSM-5(3T)@NH2-MIL-53(Al) catalyst, constructed by combining 3T cluster ZSM-5 zeolite and NH2-MIL-53(Al), and the modified AlCl3/ZSM-5(3T)@NH2-MIL-53(Al) catalyst in the disproportionation preparation of (CH3)2SiCl2. The M06-2X/def2-TZVP hybrid functional method from the Minnesota series was used to calculate the energies of all reactants, transition states, and products in the disproportionation preparation of (CH3)2SiCl2 reaction systems for five active sites (before AlCl3 loading) and one active site (after AlCl3 loading), respectively. Additionally, ZPE corrections were applied at the same computational level. The results of structural, energy, vibrational frequency, Intrinsic Reaction Coordinate (IRC)values, bond order, Electron Localization Function (ELF), and Localized Orbital Locator (LOL) analyses were matched. The results indicated that the Lewis acid catalytic active centers obtained after AlCl3 loading enhanced the catalytic performance of AlCl3/ZSM-5(3T)@NH2-MIL-53(Al).

Dynamic proton migration in dual linkage-engineered D-π-A system for photosynthesis H2O2 generation

Accelerated charge migration and proton transfer to the reaction site are critical factors for improving photocatalytic efficiency. However, realizing both simultaneously is challenging because of the sluggish water (proton source) oxidation kinetics and interdependent redox reactions. Herein, we design an imide and hydrogen bond to connect carbon nitride ports of the D-π-A system with the dual-engineered linkages. The system uses an acetylene functional group and an imidazole ring as spatially separated water oxidation and oxygen reduction reaction (ORR) catalytic centers for photogenerated charge separation, respectively. The imine bond is a bridge grafted to the oxidation site to act as a hydrogen proton trap, and the hydrogen bond formed between reduction site and carbon nitride is used as the channel for instantaneous proton delivery to the reduction center. In situ characterization confirms that the linking sites protonation optimizes the pathway of ORR to H2O2 and facilitates the *OOH intermediates generated. It is concluded that proton transport plays a critical role in optimizing photocatalytic H2O2 production. Our work provides a strategy to improve dynamic proton transfer mechanisms.

Semi-rational engineering of leucine dehydrogenase for enhanced L-tert-leucine production.

Leucine dehydrogenase (LeuDH) is a promising enzyme for the industrial production of L-tert-leucine (L-Tle), but its catalytic activity toward trimethylpyruvate (TMP) requires enhancement. In this study, we employed a semi-rational design approach involving homology modeling of LeuDH from Exiguobacterium sibiricum (EsiLeuDH) and molecular docking with TMP to predict potential mutation sites. These sites were tested using an alanine scanning strategy to assess their impact on enzymatic activity, followed by site-saturation mutagenesis and iterative saturation mutagenesis. The resulting mutant, EsiLeuDH-M3, exhibited a remarkable 306 % increase in specific enzymatic activity (104.69 U·mg-1), compared to the wild-type EsiLeuDH (WT). Molecular docking indicated that EsiLeuDH-M3 had an increased number of hydrogen bonds, improved stability, and an enlarged substrate-binding pocket. Moreover, molecular dynamics simulations suggested that EsiLeuDH-M3 possessed a more stable conformation but a more flexible pocket, allowing TMP to access the catalytic center more easily. Experiments examining the effects of different substrate concentrations on TMP bioconversion catalyzed by WT and EsiLeuDH-M3 indicated that EsiLeuDH-M3 tolerated higher TMP concentrations than the WT enzyme. Finally, L-Tle was produced using EsiLeuDH-M3 coupled with an NADH regeneration system, achieving a high conversion rate (91 %) of TMP at a substrate concentration of 0.7 M, which is expected to reduce production costs in the industrial application of L-Tle.

C-terminus processing in Tma12 is critical for its insecticidal activity

Tma12 is a fern-derived biopesticide (22 kDa) whose LPMO activity is associated with its insecticidal activity. The absence of the last 9 amino acids in the crystal structure of Tma12 suggested a possibility of its C-terminus processing. In this communication, we have shown the importance of protein C-terminus in the insecticidal activity. Additionally, we have also established the role of N-linked glycosylation in protein stability. Pichia produced (His)6 tagged Tma12 in two forms. The 30 kDa protein comprising 192 amino acid residues did not show insecticidal activity. Contrary, 24 kDa protein exhibited toxicity to whiteflies with an LC50 1.38 μg/ml. Absence of (His)6 tag in 24 kDa protein indicated processing at the C-terminus which was confirmed with deletion mutagenesis. Failure in expressing glycosylation defective mutant suggested the importance of glycans in the stability of Tma12. New findings together with earlier reports suggest that along with the N-terminal catalytic center, correct C-terminus is pivotal for anti-whitefly activity of Tma12.

Three-Dimensional Mesoporous Covalent Organic Framework for Photocatalytic Oxidative Dehydrogenation to Quinoline.

Developing precious metal-free catalysts for organic reactions under mild conditions is urgent. Herein, we report a three-dimensional covalent organic framework (3D-COF) with high crystallinity and permanent pores, termed 3D-TABPA-COF, for the oxidation of tetrahydroquinoline to quinoline. The 3D-TABPA-COF assembled based on N4,N4-bis(4'-amino-[1,1'-biphenyl]-4-yl)-[1,1'-biphenyl]-4,4'-diamine (TABPA) is the catalytic active center for the conversion of tetrahydroquinoline. The triphenylamine in the structure is an effective photosensitizer, which not only enhances the light absorption capacity but also facilitates the rapid transfer of photogenerated electrons and ensures effective carrier separation. The obtained 3D-TABPA-COF has a high specific surface area (2745.06 m2 g-1) and mesopores of 3.57 nm. This is attributed to the fact that the bor topology is not easy to interpenetrate. It can oxidize tetrahydroquinoline to obtain quinoline efficiently under visible light irradiation. In addition, we also performed various photochemical characterizations combined with density functional theory calculations to elucidate the reaction mechanism from tetrahydroquinoline to quinoline. This work provides a feasible strategy for constructing 3D-COF to achieve efficient photocatalytic organic reactions.

Construction of Interlayered Single-Atom Active Sites on Bipyridine-Based 2D Conjugated Covalent-Organic Frameworks for Boosting the C2 Products of Electrochemical CO2 Reduction.

The electrochemical carbon dioxide reduction (eCO2RR) shows great potential in the realization of carbon neutrality, which requires a dedicated catalyst design. To develop electrocatalysts that favor C2 products, herein, the synthetic protocol for engineering interlayered single-atom metal active sites on the bipyridine-linked 2D conjugated covalent-organic framework (2D c-COF) has been developed by utilizing the interlayer π-π stacking. The resultant M@BTT-BPy-COF (where M = Cu, Ni, and Fe) provides fully exposed single-atom active sites with a suitable interdistance for catalyzing the key C-C coupling in the eCO2RR process. The Faradaic efficiency of ethanol (FEethanol) exceeds 40% with M@BTT-BPy-COF at -0.8 V vs RHE, outperforming most reported COF-based electrocatalysts. Density functional calculations suggest that the proximal active sites in the pore channel of COFs are the key active sites for promoting the C-C coupling to generate ethanol product. This investigation presents a novel way to engineer single-atom catalytic centers on 2D c-COFs, displaying the great potential of 2D c-COFs in electrocatalysis.

Dual Regulation of Sensitizers and Cluster Catalysts in Metal–Organic Frameworks to Boost H2 Evolution

Dual Regulation of Sensitizers and Cluster Catalysts in Metal–Organic Frameworks to Boost H2 Evolution

Dual Regulation of Sensitizers and Cluster Catalysts in Metal-Organic Frameworks to Boost H2 Evolution.

Photocatalytic efficiency is closely correlated to visible-light absorption ability, electron transfer efficiency and catalytic center activity of photocatalysts, nevertheless, the concurrent management of these factors to improve photocatalytic efficiency remains underexplored. Herein, we proposed a sensitizer/catalyst dual regulation strategy on the polyoxometalate@Metal-Organic Framework (POM@MOF) molecular platform to construct highly efficient photocatalysts. Impressively, Ni-Sb9@UiO-Ir-C6, obtained by coupling strong sensitizing [Ir(coumarin 6)2(bpy)]+ with Ni-Sb9 POM with extremely exposed nickel site [NiO3(H2O)3], can drive H2 evolution with a turnover number of 326923, representing a record value among all the POM@MOF composite photocatalysts. This performance is over 34 times higher than that of the typical Ni4P2@UiO-Ir constructed from [Ir(ppy)2(bpy)]+ and Ni4P2 POM. systematical investigations revealed that dual regulation of sensitizing and catalytic centers endowed Ni-Sb9@UiO-Ir-C6 with strong visible-light absorption, efficient inter-component electron transfer and high catalytic activity to concurrently promote H2 evolution. This work opens up a new avenue to develop highly active POM@MOF photocatalysts by dual regulation of sensitizing/catalytic centers at the molecular level.

Tailored Metal–Organic Framework‐Based Nanozymes for Enhanced Enzyme‐Like Catalysis

AbstractThe global crisis of bacterial infections is exacerbated by the escalating threat of microbial antibiotic resistance. Nanozymes promise to provide ingenious solutions. Here, we reported a homogeneous catalytic structure of Pt nanoclusters with finely tuned metal–organic framework (ZIF‐8) channel structures for the treatment of infected wounds. Catalytic site normalization showed that the active site of the Pt aggregates structure with fine‐tuned pore modifications structure had a catalytic capacity of 14.903×105 min−1, which was 18.7 times higher than that of the Pt particles in monodisperse state in ZIF‐8 (0.793×105 min−1). In situ tests revealed that the change from homocleavage to heterocleavage of hydrogen peroxide at the interface of the nanozyme was one of the key reasons for the improvement of nanozyme activity. Density‐functional theory and kinetic simulations of the reaction interface jointly determine the role of the catalytic center and the substrate channel together. Metabolomics analysis showed that the developed nanozyme, working in conjunction with reactive oxygen species, could effectively block energy metabolic pathways within bacteria, leading to spontaneous apoptosis and bacterial rupture. This pioneering study elucidates new ideas for the regulation of artificial enzyme activity and provides new perspectives for the development of efficient antibiotic substitutes.

Constructing Asymmetric Cu Catalytic Sites for CO2 Electroreduction with Higher Selectivity to C2 Products.

The design of catalytic sites with tunable properties is considered a promising approach to advance the reduction of CO2 into valuable fuels and chemicals, as well as to achieve carbon neutrality. However, significant challenges remain in precisely constructing catalytic sites to adjust target reduction products. In this study, catalysts were derived from metal-organic frameworks (MOFs) with different coordination environments during the electrochemical CO2 reduction reaction (eCO2RR), referred to as Cu-N2O2 and Cu-N2O3, respectively. Higher selectivity towards the production of C2 products was exhibited by the Cu-N2O2-derived catalysts, characterized by asymmetric catalytic centers of Cu0 and Cu+, compared to the Cu-N2O3-derived catalysts, which contained only symmetric catalytic centers of Cu0 sites. This enhanced selectivity is attributed to the synergistic interaction between the Cu0 and Cu+ sites, facilitating the multi-electron transfer process and improving the activation of CO2. This study explores how the coordination environment affects the catalytic performance of catalysts derived from MOFs, providing valuable insights for the development of more effective catalysts aimed at CO2 reduction.

Ru0.1Mn0.9Ox Electrocatalyst for Durable Oxygen Evolution in Acid Seawater.

Currently, direct electrolysis of seawater for green hydrogen production is primarily focused on neutral and alkaline systems. However, the precipitation of calcium and magnesium ions restricts the advancement of this technology. An acidic system can effectively address this issue. Given that Ru/Ir-based catalysts with high oxygen evolution reaction (OER) activity also exhibit high chlorine evolution reaction (CER) activity, acid seawater splitting requires anodes with higher selectivity and stability compared to the other two systems. In this study, we propose a non-precious Ru0.1Mn0.9Ox as the active anode for direct acid seawater electrolysis, which exhibits a high OER selectivity and remarkable stability for more than 1200 hours. Different from the Cl--free system, *Cl occupied on Ru sites could shift the OER active center to Mn on Ru0.1Mn0.9Ox, which prevents the lattice oxygen consumed on Ru and hinders the metal site dissolution. As the CER-insensitive catalytic center, Mn activated by the introduction of Ru can adsorb a substantial amount of *OH, creating an OER-favored local environment that inhibits CER. We introduce Cl--assisted transfer of OER active sites to CER-insensitive Mn as a fundamental strategy for achieving highly selective and durable oxygen evolution in acidic seawater.

Synthetic Biomolecular Condensates: Phase-Separation Control, Cytomimetic Modelling and Emerging Biomedical Potential.

Liquid-liquid phase separation towards the formation of synthetic coacervate droplets represents a rapidly advancing frontier in the fields of synthetic biology, material science, and biomedicine. These artificial constructures mimic the biophysical principles and dynamic features of natural biomolecular condensates that are pivotal for cellular regulation and organization. Via adapting biological concepts, synthetic condensates with dynamic phase-separation control provide crucial insights into the fundamental cell processes and regulation of complex biological pathways. They are increasingly designed with the ability to display more complex and ambitious cell-like features and behaviors, which offer innovative solutions for cytomimetic modeling and engineering active materials with sophisticated functions. In this minireview, we highlight recent advancements in the design and construction of synthetic coacervate droplets; including their biomimicry structure and organization to replicate life-like properties and behaviors, and the dynamic control towards engineering active coacervates. Moreover, we highlight the unique applications of synthetic coacervates as catalytic centers and promising delivery vehicles, so that these biomimicry assemblies can be translated into practical applications.

Unveiling the versatility of the thioredoxin framework: Insights from the structural examination of Francisella tularensis DsbA1

In bacteria the formation of disulphide bonds is facilitated by a family of enzymes known as the disulphide bond forming (Dsb) proteins, which, despite low sequence homology, belong to the thioredoxin (TRX) superfamily. Among these enzymes is the disulphide bond-forming protein A (DsbA); a periplasmic thiol oxidase responsible for catalysing the oxidative folding of numerous cell envelope and secreted proteins. Pathogenic bacteria often contain diverse Dsb proteins with distinct functionalities commonly associated with pathogenesis. Here we investigate FtDsbA1, a DsbA homologue from the Gram-negative bacterium Francisella tularensis. Our study shows that FtDsbA1 shares a conserved TRX-like fold bridged by an alpha helical bundle showcased by all DsbA-like proteins. However, FtDsbA1 displays a highly unique variation on this structure, containing an extended and flexible N-terminus and secondary structural elements inserted within the core of the TRX fold itself, which together twist the overall DsbA-like architecture. Additionally, FtDsbA1 exhibits variations to the well conserved active site with an unusual dipeptide in the catalytic CXXC redox centre (CGKC), and a trans configuration for the conserved cis-proline loop, known for governing DsbA-substrate interactions. FtDsbA1’s redox properties are comparable to other DsbA enzymes, however, consistent with its atypical structure, functional analysis reveals FtDsbA1 has a high degree of substrate specificity suggesting a specialised role within F. tularensis’ oxidative folding pathway. Overall, this work underscores the remarkable malleability of the TRX catalytic core, a ubiquitous and ancestral protein fold. This not only contributes to broadening the structural and functional diversity seen within proteins utilising this core fold but will also enhance the accuracy of AI-driven protein structural prediction tools.

Two‐Dimensional Metal Covalent Organic Polymers with Dirhodium(II) Photoreduction Centers for Efficient Nitrogen Fixation

AbstractPhotocatalytic nitrogen fixation is a green method for converting N2 to NH3, but it remains a challenging task due to the lack of effective photocatalysts. Herein, a series of porous metal covalent organic polymers (MCOPs) with the integration of dinuclear rhodium(II) catalytic centers were rationally constructed for photocatalytic N2 fixation. Interestingly, the porous MCOPs had double‐layers two‐dimensional (2D) structures with the coordinated Rh(II) as the point of registry. The photocatalytic experiment showed that Rh‐TAPA with significant donor‐acceptor (D−A) features exhibited a high activity toward NH3 production with a rate of 319.8 μmol g−1 h−1. The electron transfer process, N2 adsorption and activation mechanism of RhCOPs were further investigated through comprehensive characterization, including DFT calculations and in situ characterization. This work provided a valuable insight into the photocatalytic N2 fixation process with porous materials.

Tailored Metal-Organic Framework-Based Nanozymes for Enhanced Enzyme-Like Catalysis.

The global crisis of bacterial infections is exacerbated by the escalating threat of microbial antibiotic resistance. Nanozymes promise to provide ingenious solutions. Here, we reported a homogeneous catalytic structure of Pt nanoclusters with finely tuned metal-organic framework (ZIF-8) channel structures for the treatment of infected wounds. Catalytic site normalization showed that the active site of the Pt aggregates structure with fine-tuned pore modifications structure had a catalytic capacity of 14.903 ×105 min-1, which was 18.7 times higher than that of the Pt particles in monodisperse state in ZIF-8 (0.793 ×105 min-1). In situ tests revealed that the change from homocleavage to heterocleavage of hydrogen peroxide at the interface of the nanozyme was one of the key reasons for the improvement of nanozyme activity. Density-functional theory and kinetic simulations of the reaction interface jointly determine the role of the catalytic center and the substrate channel together. Metabolomics analysis showed that the developed nanozyme, working in conjunction with reactive oxygen species, could effectively block energy metabolic pathways within bacteria, leading to spontaneous apoptosis and bacterial rupture. This pioneering study elucidates new ideas for the regulation of artificial enzyme activity and provides new perspectives for the development of efficient antibiotic substitutes.

Engineering Single Ni Sites on 3D Cage‐like Cucurbit[n]uril Ligands for Efficient and Selective CO2 Photocatalytic Reduction

AbstractSolar‐driven CO2 selective reduction with high conversion is a challenging task yet holds immense promise for both CO2 neutralization and green fuel production. Enhancing CO2 adsorption at the catalytic centre can trigger a highly efficient CO2 capture‐to‐conversion process. Herein, we introduce cucurbit[n]urils (CB[n]), a new family of molecular ligands, as a key component in the creation of a 3D cage‐like metal (nickel, Ni)‐complex molecular co‐catalyst (CB[7]‐Ni) for photocatalysis. It exhibits an unprecedented CO yield rate of 72.1 μmol ⋅ h−1 with a high selectivity of 97.9 % under visible light irradiation. To verify the origin of the carbon source in the products, a straightforward isotopic tracing method is designed based on tandem reactions. The catalytic process commences with photoelectron transfer from Ru(bpy)32+ to the Ni2+ site, resulting in the reduction of Ni2+ to Ni+. The locally enriched CO2 molecules in the cage ligand CB[7] undergo selective reduction by the Ni+ nearby to form CO product. This work exemplifies the inspiring potential of ligand structure engineering in advancing the development of efficient unanchored molecular co‐catalysts.

Engineering Single Ni Sites on 3D Cage-like Cucurbit[n]uril Ligands for Efficient and Selective CO2 Photocatalytic Reduction.

Solar-driven CO2 selective reduction with high conversion is a challenging task yet holds immense promise for both CO2 neutralization and green fuel production. Enhancing CO2 adsorption at the catalytic centre can trigger a highly efficient CO2 capture-to-conversion process. Herein, we introduce cucurbit[n]urils (CB[n]), a new family of molecular ligands, as a key component in the creation of a 3D cage-like metal (nickel, Ni)-complex molecular co-catalyst (CB[7]-Ni) for photocatalysis. It exhibits an unprecedented CO yield rate of 72.1 μmol ⋅ h-1 with a high selectivity of 97.9 % under visible light irradiation. To verify the origin of the carbon source in the products, a straightforward isotopic tracing method is designed based on tandem reactions. The catalytic process commences with photoelectron transfer from Ru(bpy)3 2+ to the Ni2+ site, resulting in the reduction of Ni2+ to Ni+. The locally enriched CO2 molecules in the cage ligand CB[7] undergo selective reduction by the Ni+ nearby to form CO product. This work exemplifies the inspiring potential of ligand structure engineering in advancing the development of efficient unanchored molecular co-catalysts.