Non‐natural Cofactor and Formate‐Driven Reductive Carboxylation of Pyruvate

A non‐natural cofactor and formate driven system for reductive carboxylation of pyruvate is presented. A formate dehydrogenase (FDH) mutant, FDH*, that favors a non‐natural redox cofactor, nicotinamide cytosine dinucleotide (NCD), for generation of a dedicated reducing equivalent at the expense of formate were acquired. By coupling FDH* and NCD‐dependent malic enzyme (ME*), the successful utilization of formate is demonstrated as both CO₂ source and electron donor for reductive carboxylation of pyruvate with a perfect stoichiometry between formate and malate. When ¹³C‐isotope‐labeled formate was used in in vitro trials, up to 53 % of malate had labeled carbon atom. Upon expression of FDH* and ME* in the model host E. coli, the engineered strain produced more malate in the presence of formate and NCD. This work provides an alternative and atom‐economic strategy for CO₂ fixation where formate is used in lieu of CO₂ and offers dedicated reducing power.     

Non-natural Cofactor and Formate-Driven Reductive Carboxylation of Pyruvate

A non-natural cofactor and formate driven system for reductive carboxylation of pyruvate is presented. A formate dehydrogenase (FDH) mutant, FDH*, that favors a non-natural redox cofactor, nicotinamide cytosine dinucleotide (NCD), for generation of a dedicated reducing equivalent at the expense of formate were acquired. By coupling FDH* and NCD-dependent malic enzyme (ME*), the successful utilization of formate is demonstrated as both CO₂ source and electron donor for reductive carboxylation of pyruvate with a perfect stoichiometry between formate and malate. When ¹³C-isotope-labeled formate was used in in vitro trials, up to 53 % of malate had labeled carbon atom. Upon expression of FDH* and ME* in the model host E. coli, the engineered strain produced more malate in the presence of formate and NCD. This work provides an alternative and atom-economic strategy for CO₂ fixation where formate is used in lieu of CO₂ and offers dedicated reducing power.     

Electron-Rich Bi Nanosheets Promote CO2⋅− Formation for High-Performance and pH-Universal Electrocatalytic CO2 Reduction

Electrochemical CO₂ reduction reaction (CO₂RR) to chemical fuels such as formate offers a promising pathway to carbon-neutral future, but its practical application is largely inhibited by the lack of effective activation of CO₂ molecules and pH-universal feasibility. Here, we report an electronic structure manipulation strategy to electron-rich Bi nanosheets, where electrons transfer from Cu donor to Bi acceptor in bimetallic Cu−Bi, enabling CO₂RR towards formate with concurrent high activity, selectivity and stability in pH-universal (acidic, neutral and alkaline) electrolytes. Combined in situ Raman spectra and computational calculations unravel that electron-rich Bi promotes CO₂⋅⁻ formation to activate CO₂ molecules, and enhance the adsorption strength of *OCHO intermediate with an up-shifted p-band center, thus leading to its superior activity and selectivity of formate. Further integration of the robust electron-rich Bi nanosheets into III–V-based photovoltaic solar cell results in an unassisted artificial leaf with a high solar-to-formate (STF) efficiency of 13.7 %.     

Energy Transfer Dynamics of Formate Decomposition on Cu(110)

Energy transfer dynamics of formate (HCOO_a) decomposition on a Cu(110) surface has been studied by measuring the angle‐resolved intensity and translational energy distributions of CO₂ emitted from the surface in a steady‐state reaction of HCOOH and O₂. The angular distribution of CO₂ shows a sharp collimation with the direction perpendicular to the surface, as represented by cosⁿ θ (n= 6). The mean translational energy of CO₂ is measured to be as low as 100 meV and is independent of the surface temperature (T _s). These results clearly indicate that the decomposition of formate is a thermal non‐equilibrium process in which a large amount of energy released by the decomposition reaction of formate is transformed into the internal energies of CO₂ molecules. The thermal non‐equilibrium features observed in the dynamics of formate decomposition support the proposed Eley–Rideal (ER)‐type mechanism for formate synthesis on copper catalysts.     

The Role of the Nucleotides in the Insertion of the bis-Molybdopterin Guanine Dinucleotide Cofactor into apo-Molybdoenzymes

The role of the GMP nucleotides of the bis-molybdopterin guanine dinucleotide (bis-MGD) cofactor of the DMSO reductase family has long been a subject of discussion. The recent characterization of the bis-molybdopterin (bis-Mo-MPT) cofactor present in the E. coli YdhV protein, which differs from bis-MGD solely by the absence of the nucleotides, now enables studying the role of the nucleotides of bis-MGD and bis-MPT cofactors in Moco insertion and the activity of molybdoenzymes in direct comparison. Using the well-known E. coli TMAO reductase TorA as a model enzyme for cofactor insertion, we were able to show that the GMP nucleotides of bis-MGD are crucial for the insertion of the bis-MGD cofactor into apo-TorA.     

DETERMINATION OF THE BINDING CONSTANT OF H14 CO−3 TO THE PHOTOSYSTEM II COMPLEX IN MAIZE CHLOROPLASTS: EFFECTS OF INHIBITORS AND LIGHT

The binding (dissociation) constant for HCO^?₃ to the photosystem II complex in maize chloroplasts is approximately 80 μM. One HCO^?₃ binds per 500–600 chlorophyll molecules. In the dark, formate is a competitive inhibitor of HCO^?₃ binding, while 3-(3′,4′-dichlorophenyl)-1, 1-dimethylurea (DCMU) inhibits HCO^?₃ binding non-competitively. Light decreases HCO^?₃ binding in the presence of formate. Light increases the binding of HCO^?₃ in the presence of DCMU. The high binding constant for HCO, discriminates strongly among the various hypotheses attempting to explain the “bicarbonate-effect” on photosystem II. The proposal by Stemler and Jursinic (Arch. Biochem. Biophys. 221, 227–237 1983), that HCO^?₃ is one of a class of monovalent anionic inhibitors of photosystem II, is favored. These anions compete for a specific binding site on the photosystem II complex.     

Joint quantum chemical and polarizable molecular mechanics investigation of formate complexes with penta- and hexahydrated Zn2+: Comparison between energetics of model bidentate,monodentate, and through-water Zn2+ binding modes and evaluation of nonadditivity effects

In order to gain an understanding of the energetics of polycoordinated Zn²⁺ binding to the formate anion (the end side chain of the Asp and Glu residues of proteins), we compare three competing binding modes in the presence of five and six water molecules: a, bidentate binding of Zn²⁺ to both formate oxygens; b, monodentate binding of Zn²⁺ to one formate oxygen; and c, through-water binding of Zn²⁺ to formate, in which the cation remains bound to its first-hydration shell waters and interacts with both formate oxygens through three water molecules. We also investigate a complex d, which is similar to c, in which formate is protonated into formic acid and one water molecule is deprotonated. The computations are carried out using the ab initio self-consistent field/MP2 with three basis sets of increasing size density functional theory, semiempirical AM1 and PM3, and the sum of interactions between fragments ab initio computed (SIBFA) molecular mechanics procedures. The summed energies of the isolated molecules making up the complexes disfavor tautomer d compared to a–c. On the other hand, the ab initio computations give the ordering of intermolecular interaction energies as d formic acid tautomer >b monodentate >a bidentate >c through-water. Whereas the first-order energy E₁ favors both inner-shell Zn²⁺ complexes with formate over the outer-shell complex, the polarization and the charge-transfer components of the second-order energy E₂ both favor the outer-shell complex over the inner-shell one, despite the increased separation between the cation and the highly polarizable formate ion. Energy balances including continuum solvation enthalpies produce an equilibration of complexes a–d. The preference favoring the monodentate complex over the bidentate one is consistent with other ab initio results for formate binding by a fully coordinated Zn²⁺ cation and with structural results from X-ray crystallography. The SIBFA results are consistent with the ab initio results, and the computed interaction energy values match the ab initio ones to within 3%. The effects of nonadditivity are analyzed in the ab initio, SIBFA, and semiempirical computations. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 1379–1390, 1999     

Interfacing Formate Dehydrogenase with Metal Oxides for the Reversible Electrocatalysis and Solar‐Driven Reduction of Carbon Dioxide

The integration of enzymes with synthetic materials allows efficient electrocatalysis and production of solar fuels. Here, we couple formate dehydrogenase ( FDH ) from Desulfovibrio vulgaris Hildenborough (DvH) to metal oxides for catalytic CO₂ reduction and report an in‐depth study of the resulting enzyme–material interface. Protein film voltammetry (PFV) demonstrates the stable binding of FDH on metal‐oxide electrodes and reveals the reversible and selective reduction of CO₂ to formate. Quartz crystal microbalance (QCM) and attenuated total reflection infrared (ATR‐IR) spectroscopy confirm a high binding affinity for FDH to the TiO₂ surface. Adsorption of FDH on dye‐sensitized TiO₂ allows for visible‐light‐driven CO₂ reduction to formate in the absence of a soluble redox mediator with a turnover frequency (TOF) of 11±1 s^?1. The strong coupling of the enzyme to the semiconductor gives rise to a new benchmark in the selective photoreduction of aqueous CO₂ to formate.     

In Situ Bismuth Nanosheet Assembly for Highly Selective Electrocatalytic CO2 Reduction to Formate

The reduction of carbon dioxide (CO₂) into value-added fuels using an electrochemical method has been regarded as a compelling sustainable energy conversion technology. However, high-performance electrocatalysts for CO₂ reduction reaction (CO₂RR) with high formate selectivity and good stability need to be improved. Earth-abundant Bi has been demonstrated to be active for CO₂RR to formate. Herein, we fabricated an extremely active and selective bismuth nanosheet (Bi-NSs) assembly via an in situ electrochemical transformation of (BiO)₂CO₃ nanostructures. The as-prepared material exhibits high activity and selectivity for CO₂RR to formate, with nearly 94% faradaic efficiency at −1.03 V (versus reversible hydrogen electrode (vs. RHE)) and stable selectivity (>90%) in a large potential window ranging from −0.83 to −1.18 V (vs. RHE) and excellent durability during 12 h continuous electrolysis. In addition, the Bi-NSs based CO₂RR/methanol oxidation reaction (CO₂RR/MOR) electrolytic system for overall CO₂ splitting was constructed, evidencing the feasibility of its practical implementation.     

Photoreduction of carbon dioxide by hydrogen and methane

Zirconium oxide is active for photoreduction of gaseous carbon dioxide to carbon monoxide with hydrogen. A stable surface species arises under the photoreduction of CO₂ on zirconium oxide, and it is identified as surface formate by infrared spectroscopy. Adsorbed CO₂ is converted to formate by photoreaction with hydrogen. The surface formate is a true reaction intermediate since CO is formed by the photoreaction of formate and CO₂; surface formate works as a reductant of carbon dioxide to yield carbon monoxide. The dependence on the wavelength of irradiation light shows that a bulk ZrO₂ is not a photoactive species. When ZrO₂ adsorbs CO₂ a new band appears in photoluminescence excitation spectrum. The photoactive species in the reaction that CO₂+H₂ yields HCOO⁻ is presumably formed by the adsorption of CO₂ on ZrO₂ surface. Hydrogen molecules play a role to supply an atomic hydrogen. Therefore, methane molecules can also be used as a reductant of carbon dioxide.     

In Situ Reconstruction of a Hierarchical Sn-Cu/SnOx Core/Shell Catalyst for High-Performance CO2 Electroreduction

The electrochemical CO₂ reduction reaction (CO₂RR) to give C₁ (formate and CO) products is one of the most techno-economically achievable strategies for alleviating CO₂ emissions. Now, it is demonstrated that the SnO_x shell in Sn_2.7Cu catalyst with a hierarchical Sn-Cu core can be reconstructed in situ under cathodic potentials of CO₂RR. The resulting Sn_2.7Cu catalyst achieves a high current density of 406.7±14.4 mA cm⁻² with C₁ Faradaic efficiency of 98.0±0.9 % at −0.70 V vs. RHE, and remains stable at 243.1±19.2 mA cm⁻² with a C₁ Faradaic efficiency of 99.0±0.5 % for 40 h at −0.55 V vs. RHE. DFT calculations indicate that the reconstructed Sn/SnO_x interface facilitates formic acid production by optimizing binding of the reaction intermediate HCOO* while promotes Faradaic efficiency of C₁ products by suppressing the competitive hydrogen evolution reaction, resulting in high Faradaic efficiency, current density, and stability of CO₂RR at low overpotentials.     

In Situ Reconstruction of a Hierarchical Sn‐Cu/SnOx Core/Shell Catalyst for High‐Performance CO2 Electroreduction

The electrochemical CO₂ reduction reaction (CO₂RR) to give C₁ (formate and CO) products is one of the most techno‐economically achievable strategies for alleviating CO₂ emissions. Now, it is demonstrated that the SnO_x shell in Sn_2.7Cu catalyst with a hierarchical Sn‐Cu core can be reconstructed in situ under cathodic potentials of CO₂RR. The resulting Sn_2.7Cu catalyst achieves a high current density of 406.7±14.4 mA cm^?2 with C₁ Faradaic efficiency of 98.0±0.9 % at ?0.70 V vs. RHE, and remains stable at 243.1±19.2 mA cm^?2 with a C₁ Faradaic efficiency of 99.0±0.5 % for 40 h at ?0.55 V vs. RHE. DFT calculations indicate that the reconstructed Sn/SnO_x interface facilitates formic acid production by optimizing binding of the reaction intermediate HCOO* while promotes Faradaic efficiency of C₁ products by suppressing the competitive hydrogen evolution reaction, resulting in high Faradaic efficiency, current density, and stability of CO₂RR at low overpotentials.     

Bioinspired Photocatalytic NADH Regeneration by Covalently Metalated Carbon Nitride for Enhanced CO2 Reduction

Natural photosynthesis is a highly unified biocatalytic system, which coupled cofactor (NAD(P)H) regeneration and enzymatic CO₂ reduction efficiently for solar energy conversion. Mimicking nature, a novel system with Rh complex covalently grafted onto NH₂-functionalized polymeric carbon nitride (NH₂-PCN) was constructed. The integrated connection of the light-harvesting and electron mediation modules as Rh_m3-N-PCN could promote the efficient NAD⁺ reduction to NADH. As a result, the integrated system exhibited a conversion of ∼66 % within 20 minutes. By further coupling in situ generated NADH with formate dehydrogenase (FDH), a photoenzymatic production of formic acid (HCOOH) from CO₂ was accomplished. Moreover, by immobilizing FDH onto a hydrophobic membrane, an enhanced HCOOH production of ∼5.0 mM can be obtained due to the concentrated CO₂ on the gas-liquid-solid three-phase interface. Our work herein provides an integrated strategy for coupling the anchored electron mediator with immobilized enzyme for enhanced artificial photosynthesis.     

Intramolecular Hydrogen Bonds Enhance Disparity in Reactivity between Isomers of Photoswitchable Sorbents and CO2: A Computational Study

Reducing the emission of greenhouse gases, such as CO₂, requires efficient and reusable capture materials. The energy for regenerating sorbents is critical to the cost of CO₂ capture. Here, we design a series of photoswitchable CO₂ capture molecules by grafting Lewis bases, which can covalently bond CO₂, to azo‐based backbones that can switch configurations upon light stimulation. The first‐principles calculations demonstrate that intramolecular hydrogen bonds are crucial for enlarging the difference of CO₂ binding strengths to the cis and trans isomers. As a result, the CO₂–sorbent interaction can be light‐adjusted from strong chemical bonding in one configuration to weak bonding in the other, which may lead to a great energy reduction in sorbent regeneration.     

Creating a Low‐Potential Redox Polymer for Efficient Electroenzymatic CO2 Reduction

Increasing greenhouse gas emissions have resulted in greater motivation to find novel carbon dioxide (CO₂) reduction technologies, where the reduction of CO₂ to valuable chemical commodities is desirable. Molybdenum‐dependent formate dehydrogenase (Mo‐FDH) from Escherichia coli is a metalloenzyme that is able to interconvert formate and CO₂. We describe a low‐potential redox polymer, synthesized by a facile method, that contains cobaltocene (grafted to poly(allylamine), Cc‐PAA) to simultaneously mediate electrons to Mo‐FDH and immobilize Mo‐FDH at the surface of a carbon electrode. The resulting bioelectrode reduces CO₂ to formate with a high Faradaic efficiency of 99±5 % at a mild applied potential of ?0.66 V vs. SHE.     

From Molecules to Materials: Computational Design of N‐Containing Porous Aromatic Frameworks for CO2 Capture

Porous aromatic frameworks (PAFs) are novel materials with diamond topology. With the aim of enhancing their CO₂ capture and storage capacity and investigating the effect of nitrogen and/or ‐COOH decorations on CO₂ adsorption in PAFs, a series of N‐containing PAFs were designed based on ab initio results. The interaction energies (E_int) between CO₂ and each six‐membered ring were calculated at the B2PLYP‐D2/def2‐TZVPP level, then the six‐membered rings with high CO₂‐binding affinity were selected and used in the PAFs. To explore the performance of the designed PAFs, the CO₂ uptake, selectivity of CO₂ over CH₄, H₂, and N₂, and the E_int value of CO₂ in PAFs were investigated by using grand canonical Monte Carlo (GCMC) simulations and ab initio calculations. This work shows that pyridine with one nitrogen atom can provide a strong physisorption site for CO₂, whereas more nitrogen atoms in heterocycles will reduce the interaction, especially at relatively low pressure. PAFs with ?COOH groups show high CO₂ capacity. Our work provides an efficient way to understand the adsorption mechanism and a supplemental approach to experimental work.     

A Sulfur-Doped Copper Catalyst with Efficient Electrocatalytic Formate Generation during the Electrochemical Carbon Dioxide Reduction Reaction

Catalysts involving post-transition metals have shown almost invincible performance on generating formate in electrochemical CO₂ reduction reaction (CO₂RR). Conversely, Cu without post-transition metals has struggled to achieve comparable activity. In this study, a sulfur (S)-doped-copper (Cu)-based catalyst is developed, exhibiting excellent performance in formate generation with a maximum Faradaic efficiency of 92 % and a partial current density of 321 mA cm⁻². Ex situ structural elucidations reveal the presence of abundant grain boundaries and high retention of S−S bonds from the covellite phase during CO₂RR. Furthermore, thermodynamic calculations demonstrate that S−S bonds can moderate the binding energies with various intermediates, further improving the activity of the formate pathway. This work is significant in modifying a low-cost catalyst (Cu) with a non-metallic element (S) to achieve comparable performance to mainstream catalysts for formate generation in industrial grade.     

A Biomimetic Nickel Complex with a Reduced CO2 Ligand Generated by Formate Deprotonation and Its Behaviour towards CO2

Reduced CO₂ species are key intermediates in a variety of natural and synthetic processes. In the majority of systems, however, they elude isolation or characterisation owing to high reactivity or limited accessibility (heterogeneous systems), and their formulations thus often remain uncertain or are based on calculations only. We herein report on a Ni?CO₂^2? complex that is unique in many ways. While its structural and electronic features help understand the CO₂‐bound state in Ni,Fe carbon monoxide dehydrogenases, its reactivity sheds light on how CO₂ can be converted into CO/CO₃^2? by nickel complexes. In addition, the complex was generated by a rare example of formate β‐deprotonation, a mechanistic step relevant to the nickel‐catalysed conversion of H_xCO_y^z? at electrodes and formate oxidation in formate dehydrogenases.     

单原子Ge助剂修饰Cu(111)晶面上CO2加氢制甲醇的机理研究

针对CO₂热催化转化制甲醇过程中CO₂吸附、活化较困难及副产物较多的问题,提出采用单原子Ge助剂修饰Cu(111)晶面的解决思路,通过密度泛函理论(DFT)计算研究了CO₂在Ge-Cu(111)晶面上加氢合成甲醇的反应机理。结果表明,单原子Ge助剂的电子调控增加了与其相邻的 Cu 原子的电子云密度,使 CO₂分子在含 Ge 活性界面上的吸附能力显著增强:CO₂在 Ge-Cu(111)晶面上的吸附能约为Cu(111)晶面的1.5倍,约为Pd改性Cu(111)晶面的2.4倍,进而使逆水煤气变换(RWGS)反应路径速控步骤的活化能降低了近 20 kJ·mol^-1,同时衍生出 3条生成甲醇的 RWGS新路径;此外,Ge-Cu(111)晶面上甲酸盐路径由于速控步骤活化能大幅上升而被禁阻,进而CO及烃类等副产物选择性大幅降低,Ge-Cu(111)晶面上CO₂加氢制甲醇选择性升高。     

单原子Ge助剂修饰Cu(111)晶面上CO2加氢制甲醇的机理研究

针对CO₂热催化转化制甲醇过程中CO₂吸附、活化较困难及副产物较多的问题,提出采用单原子Ge助剂修饰Cu (111)晶面的解决思路,通过密度泛函理论(DFT)计算研究了CO₂在Ge-Cu(111)晶面上加氢合成甲醇的反应机理。结果表明,单原子Ge助剂的电子调控增加了与其相邻的Cu原子的电子云密度,使CO₂分子在含Ge活性界面上的吸附能力显著增强：CO₂在Ge-Cu(111)晶面上的吸附能约为Cu (111)晶面的1.5倍,约为Pd改性Cu(111)晶面的2.4倍,进而使逆水煤气变换(RWGS)反应路径速控步骤的活化能降低了近20 kJ·mol^-1,同时衍生出3条生成甲醇的RWGS新路径;此外,Ge-Cu(111)晶面上甲酸盐路径由于速控步骤活化能大幅上升而被禁阻,进而CO及烃类等副产物选择性大幅降低,Ge-Cu(111)晶面上CO₂加氢制甲醇选择性升高。