Abstract Electrochemical urea synthesis via the co-reduction of CO2 and nitrogen-containing species offers an alternative route under mild conditions to conventional thermochemical processes, but remains limited by poor mechanistic understanding and the lack of general design principles. Here, using NO2– as the nitrogen source, we develop a unified descriptor-based framework for electrochemical urea synthesis based on systematic density functional theory calculations across a series of metal catalysts. We identify the adsorption free energies of *COOH and *N as distinct descriptors governing selectivity and activity, respectively. This descriptor-based decoupling reveals that intrinsic scaling relations impose a fundamental constraint on pure-metal catalysts, leading to an intrinsic activity–selectivity trade-off consistent with experimental observations. By linking these descriptors to the energetics of early C–N coupling and potential-limiting proton-coupled electron transfer steps, we establish a mechanistic foundation for understanding catalytic performance. Guided by this framework, we demonstrate that multi-site catalyst design, alloying, and strain engineering provide viable strategies to address these limitations. In particular, alloying enables deviations from pure-metal scaling relations, unlocking regions of improved catalytic performance inaccessible to pure metals. Strain, in contrast, modulates adsorption energetics within the existing descriptor space, providing additional control over activity with minimal impact on selectivity. These insights define general design principles for electrochemical urea synthesis and provide a pathway toward the rational development of catalysts with independently tunable activity and selectivity.
Abstract The direct electrocatalytic conversion of nitrate (NO3−) to ammonia (NH3) represents an effective strategy for wastewater remediation and nitrogen equilibrium regulation. Nevertheless, this reaction suffers from intrinsic limitations, particularly unfavorable adsorption of key reaction intermediates. Herein, we fabricate a Cu–Co3O4 catalyst with engineered Cu2+ electron delocalization and Co3O4 lattice distortion. Under optimized conditions, the catalyst exhibits an NH3 yield of 38.5 mg h−1 cm−2 and Faradaic efficiency (FE) reaching 99.4% in alkaline electrolytes. Experimental and theoretical investigations verify that Cu2+ substitute tetrahedrally coordinated Co sites in the Co3O4 lattice, triggering notable lattice distortion and electron density redistribution around Co and O centers. Such structural and electronic modulations further facilitate electron delocalization over Cu sites. The electron delocalization strengthens *NO3 adsorption, inhibits hydrogen evolution reaction, and decreases the activation barrier for *NO hydrogenation, thus accelerating the overall NO3− to NH3 conversion. Moreover, Zn–NO3− battery exhibits maximum power density (5.5 mW cm−2), with NH3 yield (1.93 mg h−1 cm−2) at 40 mA cm−2. This work provides a guiding design strategy for efficient spinel cobalt oxide catalysts for the synthesis of NH3 from NO3−.
Abstract Photocatalytic oxidative coupling of methane (OCM) presents a promising route for the direct conversion of methane into value-added hydrocarbons, yet it remains challenged by the need to balance efficient methane activation with the suppression of overoxidation. Herein, we report a Ag–Cr co-modified TiO2 photocatalyst featuring spatially decoupled redox active sites, which enables high-performance continuous-flow OCM. The optimized AgCr/TiO2 system delivers a C2+ hydrocarbon production rate of 2005.1 μmol g−1 h−1 with 92% selectivity, alongside stable operation for over 45 h, surpassing most reported semiconductor-based photocatalysts. In situ and time-resolved spectroscopic analyses reveal a synergistic mechanism in which metallic Ag sites and adjacent Cr species collaboratively promote charge separation and transfer. Specifically, Cr acts as a hole-trapping center that facilitates C−H activation, while metallic Ag serves as an electron sink to support oxygen reduction. This spatially separated dual-site configuration enables the selective formation of *CH3 intermediates, thereby steering the reaction pathway toward C2+ products and effectively suppressing overoxidation. This work provides valuable insights into the photocatalytic OCM, highlighting how a spatial decoupling strategy of active sites can enable efficient and selective methane activation.
Abstract Understanding the enzymatic catalytic preferences for hydroxylation or desaturation could provide useful information for the potential regulation and engineering of enzymatic activity. AlkB, a non-heme diiron-dependent alkane oxygenase that catalyzes the hydroxylation of mid-chain alkanes and also exhibits the desaturase activity toward special substrates, serves as a representative system for studying the “hydroxylation versus desaturation” dichotomy. The molecular dynamics and density functional calculations reveal that the AlkB hydroxylation reaction requires not only the presence of dioxygen but also water as a co-substrate to form the Fe-oxyl active species. The mechanism involves the coordination of O2 with iron to form an Fe(III)–O–O–· complex as the initial step, followed by hydrogen transfer between Fe(III)–O–O–· and water, O–O bond cleavage forming Fe-oxyl assisted by the H+/e– addition, hydrogen abstraction by the Fe(III)–O–· species generated via state crossing, and hydroxyl rebound, ultimately resulting in the substrate hydroxylation. Additionally, the Fe-oxyl can facilitate a hydrogen transfer between Fe-bound oxygen atoms to produce a similar Fe-oxyl species on the other iron site, which may enhance the catalytic efficiency of the enzyme. The mechanisms of substrate hydrogen abstraction directly by Fe(III)–O–O–· or Fe(III)–O–OH were found to be unfavorable. The competitive desaturation is unfavorable for dodecane, which is thought to be related to the orientation and distance between the Fe-OH group and the substrate carbon radical. Furthermore, our study explored the effects of residue mutations, providing further understanding of alkane oxygenases and the non-heme diiron enzyme family.
Abstract Mn is a well-established promoter of Co-based catalysts for enhancing the production of long-chain hydrocarbons via Fischer–Tropsch synthesis (FTS). Revealing mechanistic insights into metal–promoter interactions requires atomically defined Co surfaces with highly controlled addition of Mn. In this study, Mn was deposited onto Co(0001) single crystals to tune Mn:Co ratios relevant to FTS, while X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy were used to access the electronic and chemical alterations. Scanning tunneling microscopy revealed the MnO decoration on Co(0001) while density functional theory (DFT) was employed to correlate the atomic structure of MnO on Co(0001) and its effect on the valence band spectra. Solid–gas interactions were investigated in various atmospheres enabling in situ correlation among surface composition, structure, and catalytic conditions. We find a substrate-induced growth of MnO clusters on the Co(0001) surface. Valence band spectra and DFT calculations reveal a charge transfer between Mn and Co at the MnO–Co interface and alterations of the chemical structures. Moreover, in the presence of Mn under relevant FT reaction conditions, CO dissociation and formation of carbonaceous intermediates (–C/–CH) are enhanced, which highlights the promotional role of Mn in facilitating key steps of the Fischer–Tropsch reaction.
Abstract Glycerol electrooxidation (GEOR) is a compelling alternative to the oxygen evolution reaction (OER) in water electrolysis, lowering energy demand while simultaneously producing valuable chemicals. However, efficient and selective catalysts for GEOR remain limited, and a significant gap exists between laboratory research and industrial application. In this study, Ni-based chalcogenides and pnictogenides (NiXy, X = O, S, P, Se) were synthesized to investigate the role of heteroatoms in active-site formation and GEOR selectivity. Among the materials studied, NiSe2 exhibited the best GEOR activity, delivering 100 mA cm–2 at 1.45 VRHE while achieving ≈100% Faradaic efficiency (FEGEOR), with 95% selectivity toward formate. In situ spectroscopy, diffraction analysis, and first-principles calculations reveal that this improved performance originates from rapid γ-NiOOH formation and optimized glycerol adsorption energy. This work reports a dry-cathode zero-gap GEOR-HER electrolyzer successfully operating under industrially relevant conditions (i.e., 400 mA cm–2 at 60 °C), achieving nearly unity FEGEOR at 1.7 V with complete suppression of OER, highlighting GEOR-HER potential to enhance both energy efficiency and economic viability of electrolytic hydrogen production.
Abstract Rhynchophylline (RHY) is a spiroindole alkaloid that acts on the cardiovascular and central nervous systems. Based on the distribution patterns of 7R and 7S spiroindole alkaloids in U. rhynchophylla, we hypothesize the existence of hirsutine oxidase responsible for 7R and 7S RHY biosynthesis, respectively. However, the stereoselective oxidase has not been identified, and the mechanism underlying spiroindole formation remains unclear. In this study, we identify three hirsutine oxidases that catalyze the final step of RHY biosynthesis in U. rhynchophylla. CYP71AU491 and CYP71AU492 stereoselectively convert hirsutine (a secoyohimbine scaffold) into RHY with a 7R spiroindole configuration, whereas CYP71AU557 specifically catalyzes the formation of the 7S spiroindole scaffold. In planta validation confirms that CYP71AU491 and CYP71AU492 contribute to 7R RHY biosynthesis in U. rhynchophylla, while CYP71AU557 is involved in 7S RHY production. These enzymes are predominantly enriched in roots and hooks and are localized to the endoplasmic reticulum. Enzymatic activity is substantially enhanced by 87.3, 91.3, and 81.6%, respectively, through a combined mutation strategy (CYP71AU491-F131G + V322S, CYP71AU492-T327G + L388S, and CYP71AU557-F131G + L391S). QM/MM simulations indicate that product formation proceeds via a key Compound I−mediated epoxidation intermediate, followed by a concerted dual ring-opening process involving simultaneous C−O and C−C bond cleavage, revealing a previously unrecognized reaction mechanism. Furthermore, the chiral selectivity of the products arises from differences in substrate recognition conformations dictated by distinct binding-pocket architectures in CYP71AU492 and CYP71AU557. Overall, this study reports the identification of stereoselective hirsutine oxidases involved in RHY biosynthesis and elucidates the mechanism underlying 7R and 7S spiroindole scaffold formation. These findings resolve a key bottleneck in RHY biosynthesis and provide a foundation for advancing its biomanufacturing.
Abstract Suzuki–Miyaura cross-coupling is among the most frequently used methods to forge new C–C bonds. Organohalides are recognized as the classical electrophilic coupling partner in these reactions. However, given the abundance of oxygen in common feedstock molecules, researchers have sought improved methods to harness C–O bonds as alternatives to halides. Today, methods exist to directly cross-couple functional groups such as alcohols, carboxylic acids, and phenols. However, methods to directly engage ketones in cross-coupling reactions are lacking. Herein, we present how ketones can be utilized in the Suzuki–Miyaura cross-coupling reaction to form valuable alkenyl arenes. The reaction makes use of a Ni/bipyridine catalyst in the presence of pivalic anhydride and KOtBu. Mechanistic studies suggest that the reaction proceeds by a rapid in situ activation of the ketone to form an alkenyl pivalate intermediate, which acts as a pseudohalide in a Ni-catalyzed Suzuki–Miyaura coupling. The compatibility of the base, activating agent, and low-valent metal catalyst is shown to be central to the reaction’s success.
Abstract Among the recognized methods to build cyclopropanes via photocatalytic [2 + 1] cycloaddition, the strategy of activation of the C1 synthon is exclusively dominant, while the photocatalytic activation of C2 synthon coupled with appropriate C1 synthon remains overlooked. Herein, we disclose a visible-light photocatalytic cis-cyclopropanation of maleimides with sulfoxonium ylides under mild, metal-, and oxidant-free conditions to efficiently construct 3-azabicyclo[3.1.0]hexane derivatives. In particular, a high stereoselectivity of cis-cyclopropanation can be accomplished through solvent-bridged H-bonding interactions. A combined experimental and computational mechanistic study suggests that the activation of C2 synthon, maleimides, via photocatalytic triplet–triplet energy transfer (EnT) is achieved to conduct the [2 + 1] cycloaddition reaction with sulfoxonium ylides. The afforded bicyclic framework can undergo facile downstream transformations, delivering stereochemically defined cyclopropane derivatives. In addition, this photocatalytic [2 + 1] cycloaddition via distinct EnT activation of C2 synthon is also appropriate for coumarins to result in the cyclopropa[c]coumarin derivatives. Moreover, benzophenone imines and 2-benzoylpyridines are also suitable for the photocatalyzed [2 + 1] cycloaddition with sulfoxonium ylides via energy transfer mechanism to construct the corresponding aziridine and oxirane derivatives, respectively, demonstrating the general applicability and practicability of this approach.
Abstract A family of non-heme iron(III) complexes (1–10) bearing bis(pyridine-dioxime) scaffolds in the primary coordination sphere and diverse functional groups in the secondary coordination sphere (SCS), including o-NHMe2+-C6H4, o-OMe-C6H4, o-OH–C6H4, –C6F5, pyridine, and pyrimidine, was investigated for the catalytic oxygen reduction reaction (ORR). All the complexes showed 4e–/4H+ selectivity toward the ORR under both electrocatalytic and chemical reaction conditions. Kinetic studies indicate that the formation of a protonated Fe(O2•) intermediate is the rate-determining step for this series of catalysts. The turnover frequency (TOF) correlates with the FeIII/FeII redox potential, revealing a linear free-energy relationship (LFER) in which more electron-rich iron centers exhibit higher catalytic activity under the chemical ORR. However, complexes bearing o-OMe-C6H4 and –C6F5 substituents in the SCS display TOF values significantly higher than predicted by the LFER, highlighting the key role of these functional groups in promoting catalysis through the formation of proton-relay sites near the active center. In contrast, the complex containing an o-NHMe2+-C6H4 substituent exhibits the lowest TOF among the series, in contrast to the beneficial effect of tertiary amines previously reported for Fe(porphyrin) catalysts. Overall, this study demonstrates the crucial role of SCS interactions in modulating the activity of non-heme iron catalysts for ORR.
Abstract Replacing the sluggish oxygen evolution reaction with thermodynamically favorable small-molecule oxidation reactions enables energy-efficient hydrogen production, yet alkaline systems face an inherent conflict because neutral substrates and OH− impose incompatible demands on the interfacial hydrogen bond network. Neutral molecules require a loose network for diffusion, whereas OH− transport via the Grotthuss mechanism strictly depends on a continuous one, creating a mass transfer bottleneck that has been largely overlooked. Here, we use the hydrazine oxidation reaction (HzOR) as a model and resolve this conflict through spatially differentiated dual modulation of the interfacial hydrogen bond network via a multiscale electric field on fluorine-doped cobalt phosphide (F-CoP). The interfacial electric fields enhanced by a positive shift in the potential of zero charge drive K+ accumulation to disrupt midrange hydrogen bonds for fast N2H4 diffusion, while atomic-scale local fields at F sites anchor water molecules via hydrogen bonds to restore short-range network connectivity for efficient OH− transport. This spatially distinct mechanism enables the F‑CoP electrocatalyst to require only 0.293 V at 100 mA/cm2 for hydrazine-assisted water splitting, 1.53 V lower than conventional water splitting. This work establishes spatially resolved interfacial hydrogen bond modulation as a general framework for resolving bimolecular mass transfer conflicts in alkaline electrocatalysis.
Abstract Low-temperature CO2 hydrogenation to methane has the potential to form the basis of power-to-gas technologies, which could help close the carbon cycle and address environmental concerns. Catalysts with supported metals that can activate hydrogen are typically used for this reaction but do not yet meet the requirements of large-scale applications. Their tailored design remains challenging due to the ambiguity about the role of support and supported metal and how they interact with each other to ensure industrially relevant performance. To contribute to closing this knowledge gap, we prepared ZrO2- and YZrOx-supported catalysts possessing 1 nm Ru or Rh nanoparticles at a low metal loading of about 0.1 wt %, which was chosen for economic reasons. The best-performing Ru/ZrO2 catalyst outperformed various previously developed Ru- or/and Rh-containing catalysts in terms of metal-related activity despite operating at around 90% equilibrium conversion. To gain a detailed understanding of the kinetics and mechanism of CO2 methanation, we performed a comprehensive study combining steady-state isotopic transient kinetic analysis (SSITKA), temporal analysis of products (TAP), and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The SSITKA method enabled us to determine the concentration and the lifetime of the surface intermediates of gas-phase CH4. The concentration was found (i) to be significantly higher than that of surface atoms of Rh or Ru and (ii) to increase with increasing reaction temperature. Thus, support plays a pivotal active role in the reaction kinetics and mechanism. Moreover, a direct correlation was found between the lifetime and the strength of CO2 adsorption as determined by TAP experiments. This finding suggests that the adsorptive catalyst property is an important activity-governing factor. This property can be controlled by the degree of support reduction; the higher the reduction degree, the longer the lifetime. The reduction degree depends on the kind of supported metal and dopant for ZrO2. In situ DRIFTS studies confirmed that CO2 methanation proceeds on the support via the formate (HCOO–) and methoxy (OCH3) intermediates, ultimately yielding gas-phase CH4. The synergistic action of oxygen vacancies and weak OH– basic centers was suggested to facilitate CO2 adsorption and its rapid conversion into active HCOO– species, thereby enabling the fast formation of reaction intermediates. The coexistence of oxygen vacancies and weak OH– groups on the surface of ZrO2-based supports may provide a faster pathway for CH4 formation. Therefrom, the presented approach and the obtained knowledge may be used for the purposeful design of catalysts not only for CO2 methanation but also for CO2 hydrogenation to higher hydrocarbons to hinder the formation of CH4.
Abstract Although iron has emerged as an earth-abundant alternative for 1,3-diene coordinative polymerization, stereoselective iron systems remain uncommon and are often associated with limited catalytic activity. Here, we report three iron(II) complexes supported by 1,1-diaryl-N-(quinolin-8-yl)methanimine ligands, which upon activation with Al(iBu)3/[CPh3][B(C6F5)4] or methylaluminoxane (MAO), promote trans-1,4-selective polymerization of isoprene and β-myrcene with high activity (TOF up to 5700 h–1 at room temperature) and trans-1,4 contents of up to 95 and 99%, respectively. These systems operate under mild conditions and afford polymers with tunable molar masses by varying the monomer-to-Fe ratio. Beyond homopolymers, the catalyst platform allows the synthesis of poly(isoprene-block-myrcene) through sequential copolymerization, yielding trans-1,4-stereoregular materials. Density functional theory (DFT) calculations provide mechanistic insights into the origin of the trans-1,4 selectivity, rationalizing the experimentally observed selectivity. This work demonstrates that well-defined iron catalysts can efficiently mediate trans-selective 1,3-diene polymerization with high activity, highlighting the potential of iron for the development of precision polymerization catalysts.
Abstract A series of four silylium-ion-promoted enyne cycloisomerization reactions is reported. Various silicon-tethered 1,5-, 1,6-, and 1,7-enynes engage in chemoselective π-activation of either unsaturated branch by the formation of β,β- or β,β’-bis(silicon)-stabilized vinyl cations (from the alkyne branch) or a β-silicon-stabilized carbenium ion (from the alkene branch). Subsequent ring closures lead to a six-membered ring (silinane) in three cases, while one 1,5-enyne cyclizes to give a five-membered ring (silole). The silole system stands out as the exocyclic silyl group is lost by protolysis, followed by proton-mediated, thermodynamically controlled migration of an aryl substituent. The reaction mechanisms can be rationalized by silicon-controlled carbocation formation with termination by either allylation of a carbenium-ion intermediate with an allylsilane or a Friedel–Crafts reaction with an arene. The proton from the Wheland intermediate is captured by proton-into-silylium ion interconversion, again employing an allylsilane reagent.
Abstract Photocatalytic oxidation of methane (POM) to methanol under mild conditions remains challenging because of the difficulty in activating inert C–H bonds and the inevitable overoxidation of methanol. Herein, we simultaneously achieved high selectivity and productivity of CH3OH in POM by introducing Pd nanoclusters (NCs) on a Ce-doped TiO2 photocatalyst (Pdn/TiCeOx) at room temperature. Detailed mechanistic studies revealed that the construction of Ce–O5 sites could pre-activate the C–H bond by polarizing CH4 molecules. Furthermore, the introduced Pd NCs significantly altered the electronic structure of Ce atoms, inducing pronounced charge localization at Ce sites, thereby promoting CH4 adsorption and activation and, in turn, reducing the energy barrier for C–H cleavage by ∼0.65 eV. Meanwhile, the charge localization at Ce sites not only inhibited further dehydrogenation of the adsorbed *CH3 but also suppressed the overoxidation of *CH3OH by weakening the Ce–Om bond and strengthening the polarity of the O–H bond in CH3OH, thereby facilitating methanol desorption. As a result, Pdn/TiCeOx exhibits a CH3OH productivity of 11,620 μmol·g–1·h–1 with a selectivity of 98% in POM at ambient temperature and low pressure. This work underscores the efficacy of lanthanide-induced structural distortion and electronic engineering in oxide-based catalysts and offers a design principle for methane-to-methanol conversion.
Abstract The development of high-performance oxygen carriers (OCs) for chemical looping dry reforming of methane (CLDRM) is often hindered by the sluggish kinetics of C–H bond activation and the susceptibility to carbon deposition. Herein, we report that A-site Y doping in LaFeO3 (La0.9Y0.1FeO3) perovskite significantly enhances methane reactivity, achieving a CH4 conversion of 93–98% and a syngas yield nearly twice that of pristine LaFeO3, alongside an ideal H2/CO ratio (1.97–1.99) and stable performance at 900 °C over 30 CH4/CO2 redox cycles. Experimental and DFT analysis reveal a two-stage “active-site relay” activation mechanism. Initially, Y doping in the perovskite induces lattice distortion and enlarges Fe–O–Fe bond angles, which boosts lattice oxygen mobility and facilitates surface C–H bond cleavage. Subsequently, deep reduction triggers the in situ exsolution of metallic Fe0 nanoparticles, serving as highly active secondary centers for CH4 dissociation. The synergistic effect between exsolved Fe0 and the Y-doped perovskite with high mobility of lattice oxygen ensures rapid coke elimination, thereby enabling good cyclic stability. The strategy of the “active-site relay” can provide principles for rationally designing advanced OCs.
Abstract Nanostructuring is established as a photoelectrode performance enhancing route for solar-driven catalytic processes. However, it is often unclear to what extent the increase in photoelectrode physical surface area directly results in a commensurate increase in photoelectrochemically active surface area. While there are established methods for estimating the physical and electrochemically active surface areas, it is challenging to quantify the operando photoelectrochemically active surface area of nanostructured or nanoparticulate photoelectrodes. Herein, we demonstrate that photoinduced absorption (PIA) spectroelectrochemistry can be employed to quantify the operando photoelectrochemically active area of photoanodes for the oxygen evolution reaction (OER) by exploiting the strong dependence of OER turnover frequency on physical surface hole density. We investigate BiVO4, α-Fe2O3, and TiO2 photoanodes with contrasting morphologies – planar, nanoparticulate, and nanostructured. Our study combines operando measurements of TOF and geometric surface hole density to quantify the photoelectrochemically active surface area of each catalytic system for OER. For the nanostructured photoelectrodes, the photoelectrochemically active surface areas determined from our PIA analyses are shown to be in agreement with their physical surface area, consistent with their good OER performance. This contrasts with the low photoelectrochemically active surface areas compared to their high physical surface area determined by the nanoparticulate photoelectrodes, resulting in poor performance. We conclude by demonstrating how the photoelectrochemically active surface areas of nanoparticulate photoelectrodes increase when driving more kinetically facile reactions or by adding co-catalysts.
Abstract Electrochemical CO2 reduction (CO2RR) to multicarbon products offers a route to green chemical feedstocks. While nanostructured Copper (Cu) catalysts provide a high density of undercoordinated sites that are generally associated with enhanced C–C coupling, their practical application is hindered by rapid structural degradation under operating conditions. In this work, we demonstrate that multidentate N-heterocyclic carbene (NHC) ligands can mitigate these effects by providing enhanced surface stabilization compared to monodentate analogues. We synthesized Cu nanoparticles (CuNPs) functionalized with mono-, bi-, tridentate, and polymeric NHC ligands and evaluated their performance in CO2-saturated 0.5 M KHCO3. We found that increasing NHC denticity systematically improves ambient stability, preserves structural integrity even after cathodic electrolysis, and enhances C2 selectivity. Among the series, tripodal NHC-stabilized Cu nanoparticles achieved a ∼40% Faradaic efficiency (FE) toward C2 products which is a 60-fold increase over oleylamine-capped controls. These catalysts also exhibited a positive shift in C2 onset potential to –1.1 V vs RHE and a partial C2 current density of ∼60 mA/mg at –1.7 V vs RHE. Post-electrocatalytic analysis via FE-SEM and XPS analyses are consistent with reduced catalyst restructuring in the multidentate system. These findings identify multidentate NHC ligation as a promising strategy for designing durable, highly selective nanocatalysts for CO2 conversion.
Abstract Sustainability has become a key objective in modern synthetic chemistry, driving the adoption of earth-abundant metals in asymmetric transition-metal catalysis. Herein, we report a highly efficient iron-catalyzed asymmetric hydrosilylation of aryl ketones mediated by a chiral iron complex bearing exclusively achiral ligands, in which chirality arises solely from a stereogenic iron center. This earth-abundant chiral-at-metal catalyst combines structural simplicity with high versatility, as demonstrated by the synthesis of more than 50 chiral alcohols with yields and enantioselectivities up to >99% and >99% ee, respectively. The catalyst is capable of operating at loadings down to 0.01 mol % (TON up to 6000) and under environmentally friendly, solvent-free conditions. A key finding is the significant rate acceleration observed under blue-light irradiation. Furthermore, the system displays a pronounced positive non-linear effect driven by precipitation of the racemic catalyst, allowing for high product enantiomeric excess even when using a catalyst of low enantiopurity. The synthetic utility was demonstrated by the preparation of several pharmaceutical intermediates, such as precursors for the drugs Emend, Aficamten, and Crizotinib.
Abstract The high stability of the C–H bond and the poor redox activity of the Cr2O3 catalyst severely limit the efficient catalytic conversion of low-concentration methane. In this study, we employed an in situ carbon-doping strategy to prepare Cr2O3 catalysts with coexisting lattice-substituted carbon species and surface-stabilized carbon species. Compared to the sample without carbon doping, appropriate carbon doping improves the intrinsic catalytic activity by lowering the C–H activation barrier. It reduces the catalyst light-off temperature by 100 °C and greatly boosts its catalytic activity by 64% at 500 °C, while retaining performance over 50 h on-stream and maintaining reasonable structural stability. Based on XRD, EPR, XPS depth profiling and other characterizations, it is demonstrated that surface-stabilized carbon species generate oxygen-vacancy defects and promote lattice-oxygen activation. Furthermore, lattice-substituted carbon atoms effectively narrow the band gap of Cr2O3, which in turn reduces the energy barrier of electron transfer and ultimately induces the formation of highly active Cr5+ species on the catalyst surface. The resulting catalyst exhibits improved redox capability, which in turn promotes methane activation and initial C–H bond cleavage. These findings are corroborated by in situ DRIFTS results. This study offers a promising route to rationally construct high-performance and robust non-noble metal catalysts for methane oxidation through a carbon-doping strategy.
