Mild Route Research Articles

Regulating Atomically-Precise Pt Sites for Boosting Light-Driven Dry Reforming of Methane.

Light-driven dry reforming of methane is a promising and mild route to convert two greenhouse gas into valuable syngas. However, developing facile strategy to atomically-precise regulate the active sites and realize balanced and stable syngas production is still challenging. Herein, we developed a spatial confinement approach to precisely control over platinum species on TiO2 surfaces, from single atoms to nanoclusters. The configuration comprising single atoms and sub-nanoclusters engenders pronounced electronic metal-support interactions, with resultant interfacial states prompting surface charge rearrangement. The unique geometric and electronic properties of these atom-cluster assemblies facilitate effective activation of CH4 and CO2, accelerating intermediate coupling and minimizing side reactions. Our catalyst exhibits an outstanding syngas generation rate of 34.41 mol gPt -1 h-1 with superior durability, displaying high apparent quantum yield of 9.1 % at 365 nm and turnover frequency of 1289 h-1. This work provides insightful understanding for exploring more multi-molecule systems at an atomic scale.

Regulating Atomically‐Precise Pt Sites for Boosting Light‐Driven Dry Reforming of Methane

AbstractLight‐driven dry reforming of methane is a promising and mild route to convert two greenhouse gas into valuable syngas. However, developing facile strategy to atomically‐precise regulate the active sites and realize balanced and stable syngas production is still challenging. Herein, we developed a spatial confinement approach to precisely control over platinum species on TiO2 surfaces, from single atoms to nanoclusters. The configuration comprising single atoms and sub‐nanoclusters engenders pronounced electronic metal‐support interactions, with resultant interfacial states prompting surface charge rearrangement. The unique geometric and electronic properties of these atom‐cluster assemblies facilitate effective activation of CH4 and CO2, accelerating intermediate coupling and minimizing side reactions. Our catalyst exhibits an outstanding syngas generation rate of 34.41 mol gPt−1 h−1 with superior durability, displaying high apparent quantum yield of 9.1 % at 365 nm and turnover frequency of 1289 h−1. This work provides insightful understanding for exploring more multi‐molecule systems at an atomic scale.

Synthesis Ag-Hollandite by mild route for highly efficient ozone decomposition

Catalytic ozone (O3) decomposition is a promising technology for curbing indoor O3 pollution, whereas its application is limited by the stability and moisture resistance of heterogeneous catalysts. Ag-Hollandite is a capable solution, but its facile synthesis still lacks systematic investigation. In this study, Ag-Hollandite catalysts were prepared using AgMnO4 as the precursor by reflux (AMO-Re), hydrothermal (AMO-HT), and homogeneous (AMO-HR) methods, respectively. The as-prepared samples showed excellent stability under moisture conditions, with the optimal one maintaining an O3 conversion rate of 99.19 % after 100 h. In the characterization results, Ramsdellite (R-MnO2) was identified as an intermediate species in the synthesis. AMO-HR exhibits higher activity due to enhanced active site exposure and weakened adsorption towards *OO species, while reduced surface hydroxyl content was a crucial factor for moisture resistance. This study aims to contribute insights for preparing catalysts by a facile method.

Morphology engineering and electronic structure remodeling of manganese-incorporated VN for boosting urea-assisted energy-saving hydrogen production

Urea-assisted water electrolysis offers a promising route to reduce energy consumption for hydrogen production and meanwhile treat urea-rich wastewater. Herein, we devised a shear force-involved polyoxometalate-organic supramolecular self-assembly strategy to fabricate 3D hierarchical porous nanoribbon assembly Mn-VN cardoons. A bimetallic polyoxovanadate (POV) with the inherent structural feature of Mn surrounded by [VO6] octahedrons was introduced to trigger precise Mn incorporation in VN lattice, thereby achieving simultaneous morphology engineering and electronic structure modulation. The lattice contraction of VN caused by Mn incorporation drives electron redistribution. The unique hierarchical architecture with modulated electronic structure that provides more exposed active sites, facilitates mass and charge transfer, and optimizes the associated adsorption behavior. Mn-VN exhibits excellent activity with low overpotentials of 86 mV and 1.346 V at 10 mA/cm2 for hydrogen evolution reaction (HER) and urea oxidation reaction (UOR), respectively. Accordingly, in the two-electrode urea-assisted water electrolyzer utilizing Mn-VN as a bifunctional catalyst, hydrogen production can occur at low voltage (1.456 V@10 mA/cm2), which has the advantages of energy saving and competitive durability over traditional water electrolysis. This work provides a simple and mild route to construct nanostructures and modulate electronic structure for designing high-efficiency electrocatalysts.

Experimental and theoretical unraveling of the electrocatalytic hydrodechlorination of chlorinated phenol using Pd promoted by oxygen vacancies in TiO2 array

The electrocatalytic dichlorination (EHDC) shows a promising potential to degrade chlorinated phenols (CPs). It is also a green technology in reducing the corresponding hazardous impact on the environment. In this study, we constructed a catalytic structure which was Pd on a TiO2 array with oxygen vacancies on carbon fibre paper substrate (Pd/TiO2/CFP) by a relatively mild route. Due to the presence of the oxygen vacancies, the resulting strong metal-support interaction (SMSI) effect has been identified which featured a redistribution of spatial charge in Pd/TiO2. The electron flow from the oxygen vacancies in the TiO2 to Pd facilitated the adsorption of Pd with 4-chlorophenol (4-CP) and endowed the Pd metal with an improved chemical reaction kinetics even at a low Pd loading. Experimentally, we studied the dependence of pH, concentration of 4-CP, and working potential on the reaction conditions of EHDC. The results showed that the conversion of 4-CP reached 100 % within 180 min with an apparent rate constant of 2.9 × 10-2 min−1 and the dominant product was phenol (P). The multi-cycle test illustrated that the Pd/TiO2/CFP electrode showed superior stability. The results also revealed that the comprehensive catalytic behavior was much better than those of the Pd/CFP and the TiO2/CFP electrodes. The density function theory (DFT) calculations indicated that 4-CP was more preferably absorbed on Pd/TiO2/CFP than Pd/CFP due to the SMSI assistance. This study provides a valuable guide in the preparation of precious metal-based electrodes for EHDC with a reduced loading and cost but without performance compromise.

Efficient Solar Driven Upgrading of N2 to Urea Through Photoredox Reactions on Pt Cluster/TiO2

AbstractSynthetic nitrogen fertilizers, such as urea, are instrumental in augmenting agricultural output and addressing the demands of a growing population. Nevertheless, conventional urea production heavily relies on energy‐intensive processes. In this study, an environmentally friendly photocatalytic method is proposed for directly and selectively synthesizing urea from nitrogen (N2) and methanol (CH3OH using a Pt cluster‐decorated TiO2 catalyst (Pt cluster/TiO2). Remarkably, the Pt cluster/TiO2 exhibits outstanding urea synthesis performance with a rate of 105.68 µmol g−1 h−1 and N‐selectivity of 97.29 ± 0.79%, representing the highest level of photocatalytic urea synthesis from N2. Further analysis with density functional theory (DFT) calculation reveals that the “σ–π*” donor–acceptor interaction occurred between Pt clusters and N2, efficiently reducing the N2 hydrogenation barrier. EPR experiments demonstrate that photogenerated electrons (e−) and hole (h+) are synchronously consumed through N2 reduction and CH3OH oxidation, thereby accelerating urea synthesis. The crucial step of C─N coupling is initiated by the reaction between *NH─NH and *CHO intermediate, facilitated by the low energy barrier on Pt cluster/TiO2. This work suggests an mild route of urea production and provides profound insights into the underlying chemistry of the C─N coupling reaction, which can guide the sustainable synthesis of essential indispensable chemicals.

Radical pathways for 2,4-chromandione synthesis via photoexcitation of 4-hydroxycoumarins.

4-Hydroxycoumarins are well-known for their ground-state nucleophilic behavior, which has been widely exploited for their functionalization. Herein, we reveal a previously unexplored photochemical reactivity: upon deprotonation and excitation with purple light, 3-substituted 4-hydroxycoumarins reach an excited state and act as single-electron transfer (SET) reductants, generating radicals from stable substrates. This newfound reactivity enables the direct synthesis of 3,3-disubstituted 2,4-chromandiones via a radical dearomatization process. By enabling the incorporation of alkyl and perfluoroalkyl fragments, this protocol offers a straightforward and mild route to access synthetically valuable chromanone scaffolds featuring a quaternary stereocenter. Comprehensive photophysical studies confirmed that deprotonated 4-hydroxycoumarins are potent SET reductants in their excited state, making them suitable for initiating radical-based transformations.

Photoinduced Palladium-Catalyzed Regio- and Chemoselective Elimination of Primary Alkyl Bromides: A Mild Route to Synthesize Unactivated Terminal Olefins.

Presented is a highly efficient method for visible-light-induced regio- and chemoselective elimination of alkyl halides yielding unactivated terminal olefins vital in organic synthesis. Achieved through ligand control, the reaction exhibits remarkable regioselectivity and suppresses undesired side reactions, particularly 1,5-hydrogen atom transfer (HAT). The process favors primary alkyl halides while preserving secondary and tertiary alkyl bromides, thereby enabling the incorporation of terminal olefins in complex molecules for late-stage functionalization.

Improving the electrochemical properties of Ti3C2Tx MXene for H2S electrochemical sensor by calcination

The existence level and metabolic mechanism of hydrogen sulfide (H2S) have been proved to have an important impact on organisms, even affecting the generation and development of many neurological diseases. Therefore, it is essential to develop sensitive and accurate H2S sensors to detect H2S concentration at trace level and provide effective research tools for studying the mechanism of action of H2S on organisms. MXene is a class of two-dimensional transition metal carbonitrides with a graphene-like structure, which indicating great application prospects as a biosensor due to its large specific surface area and good conductivity. In this work, the properties of multilayer Ti3C2Tx MXene materials are optimized concerning their physical structure and functional groups. Based on the Li + intercalation method, SL-Ti3C2Tx MXene is prepared by a mild route, and its electrochemical performance is optimized by high temperature calcination under high purity argon conditions. The change in material properties at high temperature is discussed through structural and chemical analysis, and the optimal calcination temperature is determined to be 700 °C. The constructed H2S electrochemical sensor exhibits high stability and reproducibility in applications, with a detection range of 0.1–500 μM, and the detection limit is reduced to 5.77 nM.

Turning damages into benefits: Corrosion-engineered cobalt foam for highly efficient biomass upgrading coupled with H2 generation

Electrocatalysis using 5-hydroxylmethylfurfural (HMF) as a substrate to produce 2,5-furandicarboxylic (FDCA) is a potentially sustainable and mild route to harvest both value-added chemicals and clean energy hydrogen. However, the poor chemical and thermal stability of HMF has impeded its storage and industrialization. Additionally, the uncontrollability, scalability, and cost of catalyst preparation methods are rarely considered in this field. Herein, we capitalize on the spontaneous and harmful corrosion phenomenon occurring under natural conditions to prepare efficient Co-based catalysts for the electrooxidation 2,5-bis(hydroxymethyl)furan (BHMF) with more stable dihydroxy groups, coupled with hydrogen evolution. The preparation of electrocatalysts through corrosion engineering is a straightforward, cost-effective, highly feasible, and scalable approach, requiring minimal equipment. In the optimal concentration of 200 mM BHMF, an ultrahigh current density of 1981.7 mA cm−2 was achieved at 2.293 V vs. RHE, contributed by both BHMF oxidation and oxygen evolution reaction (OER). Chronoamperometric electrolysis realized efficient FDCA production with 95.4% yield and 96.5% faradaic efficiency (FE) at an ultralow potential of 1.4 V vs. RHE. Since it is etched and grown on the substrate itself, the catalyst prepared by corrosion engineering is very stable and undergoes ten successive chronoamperometric electrolysis without significant structural or performance failure. Moreover, kinetic analyses are investigated to explore the origin of catalytic activity and reaction energy barrier. Finally, to further realize the potential of FDCA and H2 production in practical application, we innovatively designed a device with a two-electrode electrolyzer and a solar cell in series to drive BHMF electrooxidation with outdoor sunlight. The complete conversion of BHMF only takes 90 min, achieving a 93.5% FDCA yield and nearly theoretical hydrogen evolution.

Microbial electrosynthetic nitrate reduction to ammonia by reversing the typical electron transfer pathway in Shewanella oneidensis

Ammonia production is a critical industrial process, and mild routes to recycle nitrates in wastewater could be a promising route to ammonia synthesis. In this study, ammonia production is demonstrated in a microbial electrosynthesis system with nitrate and an electrode as electron acceptors and donors, respectively. Based on the bidirectional extracellular electron transfer capability of Shewanella oneidensis MR-1, our microbial electrosynthetic system achieves a maximum ammonia production rate of 24.3 μg h−1·mg protein−1 with 82.5% selectivity and 33.1% cathodic efficiency and functions for several cycles over 30 days. Electrochemical analysis suggests that cytochromes c, flavins, and the flavin/c-cytochrome combination play a pivotal role. Charge transfer resistance weakens over the course of weeks, resulting in easier electron transfer. Parallel reaction monitoring proteomics suggest that reversing a typical “Mtr pathway” plays a role, and a dissimilatory nitrate to ammonia pathway is used. This work proposes a progressive route to carry out ammonia synthesis under mild conditions.

Dynamic Bond-Directed Synthesis of Stable Mesoporous Metal–Organic Frameworks under Room Temperature

Stable metal-organic frameworks (MOFs) with mesopores (2-50 nm) are promising platforms for immobilizing nanosized functional compounds, such as metal-oxo clusters, metal-sulfide quantum dots, and coordination complexes. However, these species easily decompose under acidic conditions or high temperatures, hindering their in situ encapsulation in stable MOFs, which are usually synthesized under harsh conditions involving excess acid modulators and high temperatures. Herein, we report a route for the room-temperature and acid-modulator-free synthesis of stable mesoporous MOFs and MOF catalysts with acid-sensitive species encapsulated: (1) we initially construct a MOF template by connecting stable Zr6 clusters with labile Cu-bipyridyl moieties; (2) Cu-bipyridyl moieties are subsequently exchanged by organic linkers to afford a stable version of Zr-MOFs; (3) acid-sensitive species, including polyoxometalates (POMs), CdSeS/ZnS quantum dots, and Cu-coordination cages, can be encapsulated in situ into the MOFs during step 1. The room-temperature synthesis allows the isolation of mesoporous MOFs with 8-connected Zr6 clusters and reo topology as kinetic products, which are inaccessible by traditional solvothermal synthesis. Furthermore, acid-sensitive species remain stable, active, and locked within the frameworks during MOF synthesis. We observed high catalytic activity for VX degradation by the POM@Zr-MOF catalysts as a result of the synergy between redox-active POMs and Lewis-acidic Zr sites. The dynamic bond-directed method will accelerate the discovery of large-pore stable MOFs and offer a mild route to avoid the decomposition of catalysts during MOF synthesis.

Biochar-derived flower-like Co-Mo2C spheres/g-C3N4 photocatalyst: Engineering morphology configuration and electronic structure tuning

As a class of highly recalcitrant water contaminants, pharmaceuticals and personal care products (PPCPs) have raised considerable concerns. Here, we develop a biochar-derived flower-like Co-Mo2C sphere/g-C3N4 (CMCN) heterostructure photocatalyst for typical PPCPs degradation. The flower-like Co-Mo2C nanostructure is derived from biochar, an inexpensive and ubiquitous plant byproduct. The open-up nanoflake structure with sharp edges can induce the fast charge collection and separation. DFT calculations and experimental characterizations are conducted to fundamentally understand the enhanced intrinsic photocatalytic activity of the as-prepared CMCN photocatalysts, especially the role of Co atoms. The delocalized charge density of CMCN could be rational tailored via the increasing density of state and the difference in work functions between g-C3N4 and Co-Mo2C. The electron density of Mo 3d in CMCN is increased through integrating it with Co atoms, which possess numerous delocalized electrons. Compared with the Mo2C/g-C3N4 (MCN) bulk, the CMCN catalyst displays superior photocatalytic activity for the typical PPCPs degradation, mainly arising from the multifaceted open-up surfaces of Co-Mo2C nanoflower, the higher density of electron and more efficient charge transfer ability, as well as the prolonged life time of photogenerated charge carriers. This work provides a cheap and mild route for synthesizing Co-doped Mo2C nanoflower catalyst and expands the scope of constructing high active g-C3N4 based heterostructure.

NiCo Layered Double Hydroxide Nanoarrays Grown on an Etched Ni Foam Substrate for High-Performance Supercapacitor Electrode

Nickel foam (NF) with a desirable 3D open-pore structure is extensively adopted in developing integrated electrodes, and the enhanced interaction between the electrode materials and NF substrate is recognized as an effective method for a high-performance supercapacitor electrode with a low resistance nature and high stability. In this work, an etched NF (ENF) with residual nanosheets is adopted as a novel substrate to facilitate the capacitive activity of NiCo layered double hydroxide (NiCo LDH) nanowire arrays. NiCo LDH nanosheet arrays grown on a pristine NF substrate (NiCo LDH/NF) are synthesized initially and used as a precursor. Then, the ENF substrate with a residual nanosheet is obtained by partially removing NiCo LDH nanosheet arrays in a formamide/KOH mixed solution. Subsequently, NiCo LDH nanowire arrays are hydrothermally grown on ENF to form a NiCo LDH/ENF electrode. The role of the residual nanosheet on ENF is discussed in detail, in which the content of Ni3+/Co3+ and the resistance nature of NiCo LDH/ENF can be optimized with the amount of residual nanosheets. Hence, the ENF substrate with an optimal amount of residual nanosheets is beneficial for retaining the adhesion of nanoarrays and realizing the low resistance nature in a mild route. The NiCo LDH/ENF electrode shows a capacity of 976.6 C g–1 at 1 A g–1 with excellent cyclic stability. The as-assembled NiCo LDH/ENF//activated carbon hybrid supercapacitor delivers a high specific capacitance of 150.8 F g–1 at 1 A g–1 and achieves an energy density of 67.9 Wh kg–1 at a power density of 900 W kg–1 with an excellent cycle stability with a 90.6% capacity retention after 10,000 cycles, indicating high energy density and good stability.

Efficient Recovery of Valuable Metals from Lithium-Ion Battery Cathodes Using Phytic Acid-Based Deep Eutectic Solvents at a Mild Temperature

Recycling of waste lithium-ion batteries (LIBs) requires metal leaching from the LIB cathode; however, the metal-leaching process is too challenging to be efficient, green, and mild simultaneously. Moreover, the leaching efficiency at mild conditions by green solvents is not high and needs to be improved urgently. Here, deep eutectic solvents (DESs) composed of poly(ethylene glycol) 200 (PEG) and phytic acid (PHA) are designed to leach Co from LIB cathodes with an ultrahigh metal-leaching efficiency of 0.987 at a low temperature of 80 °C for 24 h, which is much higher (ca. 0.3) than the efficiency of previously reported DESs. Moreover, the constituents (PEG and PHA) in DESs are low-cost, sustainable, and biodegradable; particularly, PHA is naturally available in legumes, cereals, dried fruits, vegetables, and other fruits, which are also edible by human beings. This work provides a super highly efficient, sustainable, and mild route for metal leaching from LIB cathodes.

CoNi2 S4 Electrode with High Mass-Loading for High-Energy-Density Supercapacitor: Role of S-Containing Anions Exchange.

Anion exchange is recognized as an effective method to regulate the composition, electronic conductivity, and electrochemical behavior of the transition metal-based compounds. In this work, anion exchange is adopted as a rational post-treatment route to facilitate the capacitive activity of CoNi2 S4 nanoparticle arrays grown on carbon cloth (CC) with high mass-loading. As soaked in saturated Na2 S solution, the CoNi2 S4 /CC electrode showed an increased capacity from 483 C g-1 to 841 C g-1 at 10 mA cm-2 with excellent rate performance and stable cycling performance, which was superior to the CoNi2 S4 /CC electrode activated by NaBH4 reduction. Anion exchange was beneficial for enhancing the crystallinity, retaining the adhesion of nanoarrays, and realizing low resistance nature in a mild route. The as-assembled CoNi2 S4 /CC//activated CC hybrid supercapacitor delivered a high areal capacitance of 1.28 F cm-2 at 5 mA cm-2 , and achieved an energy density of 0.58 mWh cm-2 at a power density of 4.5 mW cm-2 with excellent cycle stability with 90.6 % capacity retention after 10000 cycles.

Surface-sealing encapsulation of phosphotungstic acid in microporous UiO-66 as a bifunctional catalyst for transfer hydrogenation of levulinic acid to γ-valerolactone.

The efficient production of γ-valerolactone (GVL) from renewable lignocellulose that is synthesized in plants by photosynthesis to replace the declining fossil resources conforms to the principles of circular economy. Compared to direct hydrogenation by H2 molecules, catalytic transfer hydrogenation (CTH) of levulinic acid (LA) and/or its esters to GVL with organic alcohols as a hydrogen source is a much milder route. The synergistic catalysis between Lewis and Brønsted acids is indispensable in the CTH process. Considering that unsaturated coordinated Zr species could act as Lewis acid sites and phosphotungstic acid (PTA) could dissociate protons as Brønsted acid sites, UiO-66 (Zr) was thus "acidified" by encapsulating PTA in its channels to tune the ratio of Brønsted to Lewis acid sites as a bifunctional catalyst so as to better understand the catalytic structure-performance relationship in the CTH process. To address the dilemma of encapsulated PTA that is prone to leach, a rapid surface sealing strategy was adopted to establish a polyimide (PI) coating over the surface of UiO-66 introducing a space confinement effect via an anhydride-amine coupling reaction. The as-synthesized PTA/UiO-66@PI catalyst exhibited 100% of LA conversion, a 93.2% of GVL yield and high recyclability for at least five consecutive cycles. Moreover, a reaction pathway followed by esterification, hydrogenation and dealcoholization as well as a catalytic hydrogenation mechanism based on intermolecular hydride β-H transfer were proposed. Current work not only provides a high-performance and high-stability catalytic system to selectively produce GVL from LA or its esters, but also sheds light on the catalytic mechanism of the CTH process at the molecular level.

Surfactant assisted exfoliation of near infrared fluorescent silicate nanosheets.

Fluorophores that emit light in the near infrared (NIR) are advantageous in photonics and imaging due to minimal light scattering, absorption, phototoxicity and autofluorescence in this spectral region. The layered silicate Egyptian blue (CaCuSi4O10) emits as a bulk material bright and stable fluorescence in the NIR and is a promising NIR fluorescent material for (bio)photonics. Here, we demonstrate a surfactant-based (mild) exfoliation procedure to produce nanosheets (EB-NS) of high monodispersity, heights down to 1 nm and diameters <20 nm in large quantities. The approach combines planetary ball milling, surfactant assisted bath sonication and centrifugation steps. It avoids the impurities that are typical for the harsh conditions of tip-sonication. Several solvents and surfactants were tested and we found the highest yield for sodium dodecyl benzyl sulfate (SDBS) and water. The NIR fluorescence emission (λem ≈ 930-940 nm) is not affected by this procedure, is extremely stable and is not affected by quenchers. This enables the use of EB-NS for macroscopic patterning/barcoding of materials in the NIR. In summary, we present a simple and mild route to NIR fluorescent nanosheets that promise high potential as NIR fluorophores for optical applications.

Syngas as a synergistic reducing agent for selective reductive amination—a mild route to bioactive amines

Syngas (a mixture of H2and CO) is a synergistic reducing agent working much better than its components independently. In particular it allows to aminate carbonyl compounds with unstable functional groups furnishing the potential fungicides.

Selective Electrochemical Synthesis of 9-Aryl-10-sulfonyl Substituted Phenanthrene from Alkynes and Sulfonyl Hydrazides

An efficient electrochemical synthesis of sulfonated phenanthrenes via the reaction of internal alkynes with sulfonyl hydrazides has been established. The protocol does not require a metal catalyst or external oxidants, providing a green and mild route to functionalized phenanthrenes. Moreover, the compatibility of various functional groups and decagram-scale experimental conditions demonstrate the practicality of the electrochemical strategy.