Atom-Economical Synthesis of Dimethyl Carbonate from CO2 : Engineering Reactive Frustrated Lewis Pairs on Ceria with Vacancy Clusters

Boosting dimethyl carbonate synthesis from CO2 and methanol through oxygen vacancy engineering on CeO2 under thermodynamically favorable conditions

The direct conversion of greenhouse gas CO2 and low-cost CH3OH into valuable dimethyl carbonate (DMC) offers a promising low-carbon synthetic pathway, but the slow CO2 activation kinetics and entropy-decreasing nature of this reaction significantly restrict DMC yield to below 1 %. In this work, 2-cyanopyridine (2-CP) was employed as a dehydrating agent to suppress the reverse reaction between DMC and H2O, shifting the thermodynamic equilibrium in favor of DMC production. Under this thermodynamic unconstrained condition, increasing oxygen vacancies, especially in the form of oxygen vacancy clusters, promotes catalytic activity significantly. We achieve a catalytic activity of 211 mmol/(g·h) at 140 °C on H2-treated, oxygen-vacancy-clusters-rich CeO2 in the presence of 2-CP, a 1.6-fold increase compared to the activity with air-treated CeO2 under identical conditions. The DMC yield reaches 8.54 % in a 20 mL CH3OH solution with 2-CP, surpassing the calculated DMC yield of about 0.66 % from the reaction equilibrium constant under the same conditions and without using the dehydrating agent. This work suggests the importance of using a dehydrating agent and also highlights oxygen vacancy clusters as pivotal active sites to promote DMC synthesis. Achieving sustainable DMC synthesis requires further exploration, encompassing strategies such as methods for regeneration of 2-CP.

Defective Poly(heptazine imide) Nanosheets for Efficient One-Step Two-Electron Photocatalytic O2 Reduction to Medical-Like H2O2

Poly(heptazine imide) (PHI) is a promising photocatalyst for hydrogen peroxide (H2O2) production; however, enhancing its specific surface area to expose internal active sites and understanding their roles in key mechanistic steps for the H2O2 synthesis remain challenging. Here, we utilized organic cations to exfoliate bulk PHI and fabricate PHI nanosheets for producing H2O2 at a rate of 27.35 mmol g-1 h-1 under simulated solar light irradiation, outperforming most of the reported carbon nitride-based catalysts. Importantly, after 36 h of cyclic accumulation reactions in a self-created spiral flow reactor, the H2O2 concentration stabilized at 2.7 wt.%, close to medical sterilization levels. In situ spectroscopic characterizations and density functional theory calculations revealed that the exfoliation results in molecular reconfiguration of the PHI basal planes, forming the active sites to promote charge separation and electron localization. This new structure also creates midgap states, enabling direct H2O2 production via a one-step, two-electron pathway, bypassing the superoxide radical pathway. Theoretical calculations suggest that the localized electronic structure created by the active sites favors the protonation of adsorbed O2 and stabilizes the *OOH species, which converts to H2O2. This study elucidates and underscores the importance of active-site reconfiguration for efficient photocatalytic oxygen reduction reaction (ORR) pathways.

Harnessing Synergistic Cooperation of Neighboring Active Motifs in Heterogeneous Catalysts for Enhanced Catalytic Performance

Understanding the intricate interplay between catalytically active motifs in heterogeneous catalysts has long posed a significant challenge in the design of highly active and selective reactions. Drawing inspiration from biological enzymes and homogeneous catalysts, the synergistic cooperation between neighboring active motifs has emerged as a crucial factor in achieving effective catalysis. This synergistic control is often observed in natural enzymes and homogeneous systems through ligand coordination. The synergistic interaction is especially vital in reactions involving tandem or cascade steps, where distinct active motifs provide different functionalities to enable the co-activation of the reaction substrate(s). Situated within a 3D spatial domain, these catalytically active motifs can shape favorable catalytic landscapes by modulating electronic and geometric characteristics, thereby stabilizing specific intermediate or transition state species in a specific catalytic reaction. In this review, we aim to explore a diverse array of the latest heterogeneous catalytic systems that capitalize on the synergistic cooperativity between neighboring active motifs. We will delve into how such synergistic interactions can be utilized to engineer more favorable catalytic landscapes, ultimately resulting in the modulation of catalytic reactivities.

Promoting Intermediate Stabilization and Coupling for Dimethyl Carbonate Electrosynthesis

The electrocatalytic coupling of methanol and CO to produce dimethyl carbonate (DMC) is an attractive strategy for converting C1 resources into value-added products, while the controlled adsorption and coupling of two key intermediates, *CO and *OCH3, have not been demonstrated yet. Herein, a heterointerface engineering strategy is developed to modulate intermediate adsorption and facilitate the C─O bond formation. By constructing a Pd and PdO heterostructure catalyst with abundant interfaces (designated as Pd/PdO-r), the Pd0 sites serve to stabilize *CO and the electrophilic Pd2+ sites can promote the *OCH3 adsorption, thereby optimizing their spatial proximity and reactivity. In addition, the heterointerfaces allow to lower the coupling reaction barrier, enabling an efficient electrocatalytic pathway for the DMC synthesis. Consequently, the Pd/PdO-r heterostructure catalyst exhibited a high Faradaic efficiency of 86% with a DMC yield rate of 252 µmol h-1 mgcat -1 in flow cells. The work suggests an effective approach to design heterointerfaces for enhanced intermediate adsorption and coupling, thus promoting the formation of valuable multicarbon products from C1 resources.

Engineering triple O-Ti-O vacancy associates for efficient water-activation catalysis

Defect engineering can create various vacancy configurations in catalysts by finely tuning the local electronic and geometric structures of the active sites. However, achieving precise control and identification of these defects remains a significant challenge, and the origin of vacancy configurations in catalysts, especially clustered or associated ones, remains largely unknown. Herein, we successfully achieve the controllable fabrication and quantitative identification of triple O-Ti-O vacancy associate (VOVTiVO) in nanosized Ni-doped TiO2. Experimental and theoretical analyses demonstrate that terminal hydroxyls adsorbed at unsaturated cationic sites play an essential role in boosting VOVTiVO formation, which enhances H2O dissociation and facilitates dissociative OH* deprotonation for defect site regeneration. In contrast, a single VO can be easily saturated by dissociative bridging hydroxyl accumulation, leading to a gradual decrease in the number of active sites. The essential role of VOVTiVO in the Ni-doped TiO2 is evidenced by its comparable catalytic performance in the hydrogen evolution reaction and hydrodechlorination reactions. Our work highlights the importance of engineering vacancy-associated active sites and presents a notable approach for designing highly active and selective catalysts for efficient H2O-involved reactions.

Advanced systems for enhanced CO2 electroreduction

Carbon dioxide (CO2) electroreduction has extraordinary significance in curbing CO2 emissions while simultaneously producing value-added chemicals with economic and environmental benefits. In recent years, breakthroughs in designing catalysts, optimizing intrinsic activity, developing reactors, and elucidating reaction mechanisms have continuously driven the advancement of CO2 electroreduction. However, the industrialization of CO2 electroreduction remains a challenging task, with high energy consumption, high costs, limited reaction products, and restricted application scenarios being the issues that urgently need to be addressed. To accelerate the progress of CO2 electroreduction towards practical application, this review shifts the research focus from catalysts to aspects such as reactions and systems, aiming to improve reaction efficiency, reduce technical costs, expand the range of products, and enhance selectivity, offering readers a new perspective. In particular, innovative and specific design strategies such as CO2 reduction coupled with alternative oxidation, co-reduction reaction of CO2 and C/N/O/S-containing species, cascade systems, and integrated CO2 capture and reduction systems are discussed in detail. Additionally, personal views on the opportunities and future challenges of the aforementioned innovative strategies are provided, offering new insights for the future research and development of CO2 electroreduction.

Defects Calculation and Accelerated Interfacial Charge Transfer in a Photoactive MOF-Based Heterojunction

Photocatalytic hydrogen production is currently considered a clean and sustainable route to meet the energy and environmental issues. Among, heterojunction photocatalysts have been developed to improve their photocatalytic efficiency. Defect engineering of heterojunction photocatalysts is attractive due to it can perform as electron trap and change the band structure to optimize the interfacial separation rate of photogenerated electron-hole pairs. Here, the MOF-based heterojunction photocatalysts with theoretically high reduction and oxidation abilities are successfully synthesized, denoted ZrO2/Pt/Zr-MOF-X, with tuned linker defectivity through an in situ electrochemical route. The defectivity are rationally calculated from the TG and 1H NMR results. A positive correlation is found between the defectivity and photocatalytic activity, and ZrO2/Pt/Zr-MOF-6 with the optimized defectivity of ca. 35% exhibits the highest hydrogen production rate of up to 2923 µmol g-1 h-1, illustrating the importance of structural defects in heterojunction photocatalysts. Ultrafast transient absorption spectroscopy and electron spin resonance results unveil the highest carrier concentration and charge separation efficiency in the defected heterostructure of ZrO2/Pt/Zr-MOF-6 through a direct Z-scheme contact, leading to its efficient photocatalysis through the high redox power.

Constructing Atomic Tungsten-Based Solid Frustrated-Lewis-Pair Sites with d-p Interactions for Selective CO2 Photoreduction

Solid frustrated Lewis pair (FLP) shows remarkable advantages in the activation of small molecules such as CO2, owing to the strong orbital interactions between FLP sites and reactant molecules. However, most of the currently constructed FLP sites are randomly distributed and easily reunited on the surface of catalysts, resulting in a low utilization rate of FLP sites. Herein, atomic tungsten-based FLP (N···WSA FLP) sites are constructed for photocatalytic CO2 conversion through introducing W single-atoms into polymeric carbon nitride. In the atomically dispersed N···WSA FLP, the electron-deficient W single-atom acts as the Lewis acid (LA), and the adjacent electron-rich N atom acts as the Lewis base. Through the combination of various characterizations, including pyridine-IR, in situ diffuse reflectance infrared Fourier transform spectroscopy, CO2-temperature programmed desorption, and theoretical calculations, the positive effects of N···WSA FLP on photocatalytic CO2 reduction are well revealed. The N···WSA FLP can effectively adsorb CO2 to form an unusual W-O-C-N structure with significant d-p orbital interactions, which leads to an interesting "push-push" electron transfer effect. The π back-donation from W 5d to the antibonding orbital (2π) of CO2 realizes reverse electron transfer from the W single-atom to the O site, while the electrons are transferred from the electron-rich N site to the electropositive C site via Lewis acid-base interactions, therefore effectively breaking the C═O bond to activate CO2 molecules and boost CO2-to-CO performance. This work provides a brand new route for the research on high-efficiency activation of small molecules based on single-atom-based FLP catalysts.

Ceria-Catalysed Production of Dimethyl Carbonate from Methanol and CO2: Effect of Using a Dehydrating Agent Combined with a Solid Cocatalyst

The direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol over ceria-based catalysts, in the presence of a dehydrating agent shifting the thermodynamical equilibrium of the reaction, has received significant interest recently. In this work, several dehydrating agents, such as molecular sieves, 2,2-dimethoxypropane (DMP), dimethoxymethane (DMM) and 1,1,1-trimethoxymethane (TMM), are combined with commercial ceria to compare their influence on the DMC yield obtained under the same set of operating conditions. TMM is found to be the most efficient; however, its conversion is not complete even after 48 h of reaction. Therefore, it is proposed for the very first time, to the best of our knowledge, to add a second solid cocatalyst in the reaction medium to accelerate the TMM hydration reaction without degrading the DMC already formed. Basic oxides and acidic zeolites with different Si/Al ratios are employed to accelerate the hydration of TMM, so as to improve the DMC yield. 13X was identified as the best option to play this role. Finally, three different commercial cerias are tested in the presence of TMM and molecular sieve 13X as the second catalyst. The most efficient combination of ceria, TMM, and molecular sieve 13X is ultimately tested in a 250 mL autoclave to start to scale up the process. A very high DMC production of 199.5 mmol DMC/gcat. is obtained.

Symmetry-Broken Steered Delocalization State in a Single-Atom Photocatalyst

Single-atom catalysts (SACs) that feature uniform metal active sites with symmetry configurations hold great promise in photocatalysis, while their catalytic efficiency is often restricted by the insufficient inherent activity. Drawing inspiration from hard-soft acid-base theory, here we propose that the delocalized electronic state of single-atom centers can be selectively modulated by adjusting their coordination symmetry, thereby optimizing the adsorption and activation of the reactant molecules. By taking ceria-based Ru-SAC (Ru-CeO2) as an example, we show that after introducing symmetry breaking, the Ru-CeO2 with an asymmetric Ru-O4 configuration (named P-Ru-CeO2) exhibits highly delocalized electrons with a soft acidic nature, leading to a much higher photocatalytic performance than for pristine Ru-CeO2 and CeO2 counterparts. The corresponding inherent mechanism was systematically investigated by spectroscopy and theoretical studies. This work provides an effective strategy for the design and controllable modulation of atomically dispersed catalysts with symmetry-broken configurations, thereby advancing applications in photocatalysis.

Direct cleavage of C=O double bond in CO2 by the subnano MoOx surface on Mo2N

Compared to H2-assisted activation mode, the direct dissociation of CO2 into carbonyl (*CO) with a simplified reaction route is advantageous for CO2-related synthetic processes and catalyst upgrading, while the stable C = O double bond makes it very challenging. Herein, we construct a subnano MoO3 layer on the surface of Mo2N, which provides a dynamically changing surface of MoO3↔MoOx (x < 3) for catalyzing CO2 hydrogenation. Rich oxygen vacancies on the subnano MoOx surface with a high electron donating capacity served as a scissor to directly shear the C = O double bond of CO2 to form CO at a high rate. The O atoms leached in CO2 dissociation are removed timely by H2 to regenerate active oxygen vacancies. Owing to the greatly enhanced dissociative activation of CO2, this MoOx/Mo2N catalyst without any supported active metals shows excellent performance for catalyzing CO2 hydrogenation to CO. The construction of highly disordered defective surface on heterostructures paves a new pathway for molecule activation.

Strikingly Facile Cleavage of N-H/N-O Bonds Induced by Surface Frustrated Lewis Pair on CeO2(110) to Boost NO Reduction by NH3

Ceria with surface solid frustrated Lewis pairs (FLPs), formed by regulating oxygen vacancies, demonstrate remarkable ability in activating small molecules. In this work, we extended the application of FLPs on CeO2(110) to the selective catalytic reduction of NO by NH3 (NH3-SCR), finding a notable enhancement in performance compared to ordinary CeO2(110). Additionally, an innovative approach involving H2 treatment was discovered to increase the number of FLPs, thereby further boosting the NH3-SCR efficiency. Typically, NH3-SCR on regular CeO2 follows the Eley-Rideal (E-R) mechanism. However, density functional theory (DFT) calculations revealed a significant reduction in the energy barriers for the activation of N-O and N-H bonds under the Langmuir-Hinshelwood (L-H) mechanism with FLPs present. This transition shifted the reaction mechanism from the E-R pathway on regular R-CeO2 to the L-H pathway on FLP-rich FR-CeO2, as corroborated by the experimental findings. The practical application of FLPs was realized by loading MoO3 onto FLP-rich FR-CeO2, leveraging the synergistic effects of acidic sites and FLPs. This study provides profound insights into how FLPs facilitate N-H/N-O bond activation in small molecules, such as NH3 and NO, offering a new paradigm for catalyst design based on catalytic mechanism research.

Amorphous FeSnOx Nanosheets with Hierarchical Vacancies for Room-Temperature Sodium-Sulfur Batteries

Room-temperature sodium-sulfur (RT Na-S) batteries, noted for their low material costs and high energy density, are emerging as a promising alternative to lithium-ion batteries (LIBs) in various applications including power grids and standalone renewable energy systems. These batteries are commonly assembled with glass fiber membranes, which face significant challenges like the dissolution of polysulfides, sluggish sulfur conversion kinetics, and the growth of Na dendrites. Here, we develop an amorphous two-dimensional (2D) iron tin oxide (A-FeSnOx) nanosheet with hierarchical vacancies, including abundant oxygen vacancies (Ovs) and nano-sized perforations, that can be assembled into a multifunctional layer overlaying commercial separators for RT Na-S batteries. The Ovs offer strong adsorption and abundant catalytic sites for polysulfides, while the defect concentration is finely tuned to elucidate the polysulfides conversion mechanisms. The nano-sized perforations aid in regulating Na ions transport, resulting in uniform Na deposition. Moreover, the strategic addition of trace amounts of Ti3C2 (MXene) forms an amorphous/crystalline (A/C) interface that significantly improves the mechanical properties of the separator and suppresses dendrite growth. As a result, the task-specific layer achieves ultra-light (~0.1 mg cm-2), ultra-thin (~200 nm), and ultra-robust (modulus=4.9 GPa) characteristics. Consequently, the RT Na-S battery maintained a high capacity of 610.3 mAh g-1 and an average Coulombic efficiency of 99.9 % after 400 cycles at 0.5 C.

Homogeneous and Heterogeneous Frustrated Lewis Pairs for the Activation and Transformation of CO2

Due to the serious ecological problems caused by the high CO2 content in the atmosphere, reducing atmospheric CO2 has attracted widespread attention from academia and governments. Among the many ways to mitigate CO2 concentration, the capture and comprehensive utilization of CO2 through chemical methods have obvious advantages, whose key is to develop suitable adsorbents and catalysts. Frustrated Lewis pairs (FLPs) are known to bind CO2 through the interaction between unquenched Lewis acid sites/Lewis base sites with the O/C of CO2, simultaneously achieving CO2 capture and activation, which render FLP better potential for CO2 utilization. However, how to construct efficient FLP targeted for CO2 utilization and the mechanism of CO2 activation have not been systematically reported. This review firstly provides a comprehensive summary of the recent advances in the field of CO2 capture, activation, and transformation with the help of FLP, including the construction of homogeneous and heterogeneous FLPs, their interaction with CO2, reaction activity, and mechanism study. We also illustrated the challenges and opportunities faced in this field to shed light on the prospective research.

Finding Natural, Dense, and Stable Frustrated Lewis Pairs on Wurtzite Crystal Surfaces for Small-Molecule Activation

The surface frustrated Lewis pairs (SFLPs) open up new opportunities for substituting noble metals in the activation and conversion of stable molecules. However, the applications of SFLPs on a larger scale are impeded by the complex construction process, low surface density, and sensitivity to the reaction environment. Herein, wurtzite-structured crystals such as GaN, ZnO, and AlP are found for developing natural, dense, and stable SFLPs. It is revealed that the SFLPs can naturally exist on the (100) and (110) surfaces of wurtzite-structured crystals. All the surface cations and anions serve as the Lewis acid and Lewis base in SFLPs, respectively, contributing to the surface density of SFLPs as high as 7.26×1014 cm-2. Ab initio molecular dynamics simulations indicate that the SFLPs can keep stable under high temperatures and the reaction atmospheres of CO and H2O. Moreover, outstanding performance for activating the given small molecules is achieved on these natural SFLPs, which originates from the optimal orbital overlap between SFLPs and small molecules. Overall, these findings not only provide a simple method to obtain dense and stable SFLPs but also unfold the nature of SFLPs toward the facile activation of small molecules.

CeO2-Based Frustrated Lewis Pairs via Defective Engineering: Formation Theory, Site Characterization, and Small Molecule Activation

Activation of small molecules is considered to be a central concern in the theoretical investigation of environment- and energy-related catalytic conversions. Sub-nanostructured frustrated Lewis pairs (FLPs) have been an emerging research hotspot in recent years due to their advantages in small molecule activation. Although the progress of catalytic applications of FLPs is increasingly reported, the fundamental theories related to the structural formation, site regulation, and catalytic mechanism of FLPs have not yet been fully developed. Given this, it is attempted to demonstrate the underlying theory of FLPs formation, corresponding regulation methods, and its activation mechanism on small molecules using CeO2 as the representative metal oxide. Specifically, this paper presents three fundamental principles for constructing FLPs on CeO2 surfaces, and feasible engineering methods for the regulation of FLPs sites are presented. Furthermore, cases where typical small molecules (e.g., hydrogen, carbon dioxide, methane oxygen, etc.) are activated over FLPs are analyzed. Meanwhile, corresponding future challenges for the development of FLPs-centered theory are presented. The insights presented in this paper may contribute to the theories of FLPs, which can potentially provide inspiration for the development of broader environment- and energy-related catalysis involving small molecule activation.

Unveiling the Synergistic Role of Frustrated Lewis Pairs in Carbon-Encapsulated Ni/NiOx Photothermal Cocatalyst for Enhanced Photocatalytic Hydrogen Production

The development of high-density and closely spaced frustrated Lewis pairs (FLPs) is crucial for enhancing catalyst activity and accelerating reaction rates. However, constructing efficient FLPs by breaking classical Lewis bonds poses a significant challenge. Here, this work has made a pivotal discovery regarding the Jahn-Teller effect during the formation of grain boundaries in carbon-encapsulated Ni/NiOx (Ni/NiOx@C). This effect facilitates the formation of high-density O (VO) and Ni (VNi) vacancy sites with different charge polarities, specifically FLP-VO-C basic sites and FLP-VNi-C acidic sites. The synergistic interaction between FLP-VO-C and FLP-VNi-C sites not only reduces energy barriers for water adsorption and splitting, but also induces a strong photothermal effect. This mutually reinforcing effect contributes to the exceptional performance of Ni/NiOx@C as a cocatalyst in photothermal-assisted photocatalytic hydrogen production. Notably, the Ni/NiOx@C/g-C3N4 (NOCC) composite photocatalyst exhibits remarkable hydrogen production activity with a rate of 10.7 mmol g-1 h-1, surpassing that of the Pt cocatalyst by 1.76 times. Moreover, the NOCC achieves an impressive apparent quantum yield of 40.78% at a wavelength of 380 nm. This work paves the way for designing novel defect-state multiphase cocatalysts with high-density and adjacent FLP sites, which hold promise for enhancing various catalytic reactions.

Photocatalytic toluene oxidation with nickel-mediated cascaded active units over Ni/Bi2WO6 monolayers

Adsorption and activation of C-H bonds by photocatalysts are crucial for the efficient conversion of C-H bonds to produce high-value chemicals. Nevertheless, the delivery of surface-active oxygen species for C-H bond oxygenation inevitably needs to overcome obstacles due to the separated active centers, which suppresses the catalytic efficiency. Herein, Ni dopants are introduced into a monolayer Bi2WO6 to create cascaded active units consisting of unsaturated W atoms and Bi/O frustrated Lewis pairs. Experimental characterizations and density functional theory calculations reveal that these special sites can establish an efficient and controllable C-H bond oxidation process. The activated oxygen species on unsaturated W are readily transferred to the Bi/O sites for C-H bond oxygenation. The catalyst with a Ni mass fraction of 1.8% exhibits excellent toluene conversion rates and high selectivity towards benzaldehyde. This study presents a fascinating strategy for toluene oxidation through the design of efficient cascaded active units.

Dimethyl Carbonate Synthesis from CO2 over CeO2 with Electron-Enriched Lattice Oxygen Species

Direct synthesis of dimethyl carbonate (DMC) from CO2 plays an important role in carbon neutrality, but its efficiency is still far from the practical application, due to the limited understanding of the reaction mechanism and rational design of efficient catalyst. Herein, abundant electron-enriched lattice oxygen species were introduced into CeO2 catalyst by constructing the point defects and crystal-terminated phases in the crystal reconstruction process. Benefitting from the acid-base properties modulated by the electron-enriched lattice oxygen, the optimized CeO2 catalyst exhibited a much higher DMC yield of 22.2 mmol g-1 than the reported metal-oxide-based catalysts at the similar conditions. Mechanistic investigations illustrated that the electron-enriched lattice oxygen can provide abundant sites for CO2 adsorption and activation, and was advantageous of the formation of the weakly adsorbed active methoxy species. These were facilitating to the coupling of methoxy and CO2 for the key *CH3OCOO intermediate formation. More importantly, the weakened adsorption of *CH3OCOO on the electron-enriched lattice oxygen can switch the rate-determining-step (RDS) of DMC synthesis from *CH3OCOO formation to *CH3OCOO dissociation, and lower the corresponding activation barriers, thus giving rise to a high performance. This work provides insights into the underlying reaction mechanism for DMC synthesis from CO2 and methanol and the design of highly efficient catalysts.

Regulating Local Atomic Environment around Vacancies for Efficient Hydrogen Evolution

Defect engineering is essential for the development of efficient electrocatalysts at the atomic level. While most work has focused on various vacancies as effective catalytic modulators, little attention has been paid to the relation between the local atomic environment of vacancies and catalytic activities. To face this challenge, we report a facile synthetic approach to manipulate the local atomic environments of vacancies in MoS2 with tunable Mo-to-S ratios. Our studies indicate that the MoS2 with more Mo terminated vacancies exhibits better hydrogen evolution reaction (HER) performance than MoS2 with S terminated vacancies and defect-free MoS2. The improved performance originates from the adjustable orbital orientation and distribution, which is beneficial for regulating H adsorption and eventually boosting the intrinsic per-site activity. This work uncovers the underlying essence of the local atomic environment of vacancies on catalysis and provides a significant extension of defect engineering for the rational design of transition metal dichalcogenides (TMDs) catalysts and beyond.

Enhancing the Green Synthesis of Glycerol Carbonate: Carboxylation of Glycerol with CO2 Catalyzed by Metal Nanoparticles Encapsulated in Cerium Metal-Organic Frameworks

The reaction of glycerol with CO2 to produce glycerol carbonate was performed successfully in the presence of gold nanoparticles (AuNPs) supported by a metal-organic framework (MOF) constructed from mixed carboxylate (terephthalic acid and 1,3,5-benzenetricarboxylic acid). The most efficient were two AuNPs@MOF catalysts prepared from pre-synthesized MOF impregnated with Au3+ salt and subsequently reduced to AuNPs using H2 (catalyst 4%Au(H2)@MOF1) or reduced with NaBH4 (catalyst 4%Au@PEI-MOF1). Compared to existing catalysts, AuNPs@MOFs require simple preparation and operate under mild and sustainable conditions, i.e., a much lower temperature and the lowest CO2 overpressure ever reported, with MgCO3 having been found to be the optimal dehydrating agent. Although the yield of the process is still not competitive with previously developed systems, the most promising advantage is the highest TOF (78 h-1) ever reported for this reaction. The optimal parameters observed for AuNPs were also tested on AgNPs and CuNPs with promising results, suggesting their great potential for industrial application. The catalysts were characterized by XRD, TEM, SEM-EDS, ICP-MS, XPS, and porosity measurements, confirming that AuNPs are present in low concentration, uniformly distributed, and confined to the cavities of the MOF.

Dynamically Reconstructed Triple-Copper-Vacancy Associates Confined in Cu Nanowires Enabling High-Rate and Selective CO2 Electroreduction to C2+ Products

Electrochemically reconstructed Cu-based catalysts always exhibit enhanced CO2  electroreduction performance; however, it still remains ambiguous whether the reconstructed Cu vacancies have a substantial impact on CO2 -to-C2+ reactivity. Herein, Cu vacancies are first constructed through electrochemical reduction of Cu-based nanowires, in which high-angle annular dark-field scanning transmission electron microscopy image manifests the formation of triple-copper-vacancy associates with different concentrations, confirmed by positron annihilation lifetime spectroscopy. In situ attenuated total reflection-surface enhanced infrared absorption spectroscopy discloses the triple-copper-vacancy associates favor *CO adsorption and fast *CO dimerization. Moreover, density-functional-theory calculations unravel the triple-copper-vacancy associates endow the nearby Cu sites with enriched and disparate local charge density, which enhances the *CO adsorption and reduces the CO-CO coupling barrier, affirmed by the decreased *CO dimerization energy barrier by 0.4 eV. As a result, the triple-copper-vacancy associates confined in Cu nanowires achieve a high Faradaic efficiency of over 80% for C2+ products in a wide current density range of 400-800 mA cm-2 , outperforming most reported Cu-based electrocatalysts.

Surface Activation by Single Ru Atoms for Enhanced High-Temperature CO2 Electrolysis

Cathodic CO2 adsorption and activation is essential for high-temperature CO2 electrolysis in solid oxide electrolysis cells (SOECs). However, the component of oxygen ionic conductor in the cathode displays limited electrocatalytic activity. Herein, stable single Ruthenium (Ru) atoms are anchored on the surface of oxygen ionic conductor (Ce0.8 Sm0.2 O2-δ , SDC) via the strong covalent metal-support interaction, which evidently modifies the electronic structure of SDC surface for favorable oxygen vacancy formation and enhanced CO2 adsorption and activation, finally evoking the electrocatalytic activity of SDC for high-temperature CO2 electrolysis. Experimentally, SOEC with the Ru1 /SDC-La0.6 Sr0.4 Co0.2 Fe0.8 O3-δ cathode exhibits a current density as high as 2.39 A cm-2 at 1.6 V and 800 °C. This work expands the application of single atom catalyst to the high-temperature electrocatalytic reaction in SOEC and provides an efficient strategy to tailor the electronic structure and electrocatalytic activity of SOEC cathode at the atomic scale.

Phase Engineering and Synchrotron-Based Study on Two-Dimensional Energy Nanomaterials

In recent years, there has been significant interest in the development of two-dimensional (2D) nanomaterials with unique physicochemical properties for various energy applications. These properties are often derived from the phase structures established through a range of physical and chemical design strategies. A concrete analysis of the phase structures and real reaction mechanisms of 2D energy nanomaterials requires advanced characterization methods that offer valuable information as much as possible. Here, we present a comprehensive review on the phase engineering of typical 2D nanomaterials with the focus of synchrotron radiation characterizations. In particular, the intrinsic defects, atomic doping, intercalation, and heterogeneous interfaces on 2D nanomaterials are introduced, together with their applications in energy-related fields. Among them, synchrotron-based multiple spectroscopic techniques are emphasized to reveal their intrinsic phases and structures. More importantly, various in situ methods are employed to provide deep insights into their structural evolutions under working conditions or reaction processes of 2D energy nanomaterials. Finally, conclusions and research perspectives on the future outlook for the further development of 2D energy nanomaterials and synchrotron radiation light sources and integrated techniques are discussed.

Polarized Active Pairs at Grain Boundary Boost CO2 Chemical Fixation

The chemical fixation of CO2 as a C1 feedstock is considered one of the most promising ways to obtain long-chain chemicals, but its efficiency was limited by the ineffective activation of CO2. Herein, we propose a grain boundary engineering strategy to construct polarized active pairs with electron poor-rich character for effective CO2 activation. By taking CeO2 as a model system, we illustrate that the polarized "Ce4+-Ce3+-Ce4+" pairs at the grain boundary can simultaneously accept and donate electrons to coordinate with O and C, respectively, in CO2. By the combination of synchrotron radiation in situ technique and density functional theory calculations, the mechanism of the catalytic reaction has been systematically investigated. As a result, the CeO2 nanosheets with a rich grain boundary show a high DMC yield of 60.3 mmol/gcat with 100% atomic economy. This study provides a practical way for the chemical fixation of CO2 to high-value-added chemicals via grain boundary engineering.

Enhancing polyol/sugar cascade oxidation to formic acid with defect rich MnO2 catalysts

Oxidation of renewable polyol/sugar into formic acid using molecular O₂ over heterogeneous catalysts is still challenging due to the insufficient activation of both O₂ and organic substrates on coordination-saturated metal oxides. In this study, we develop a defective MnO₂ catalyst through a coordination number reduction strategy to enhance the aerobic oxidation of various polyols/sugars to formic acid. Compared to common MnO₂, the tri-coordinated Mn in the defective MnO₂ catalyst displays the electronic reconstruction of surface oxygen charge state and rich surface oxygen vacancies. These oxygen vacancies create more Mn^δ+ Lewis acid site together with nearby oxygen as Lewis base sites. This combined structure behaves much like Frustrated Lewis pairs, serving to facilitate the activation of O₂, as well as C-C and C-H bonds. As a result, the defective MnO₂ catalyst shows high catalytic activity (turnover frequency: 113.5 h^-1) and formic acid yield (>80%) comparable to noble metal catalysts for glycerol oxidation. The catalytic system is further extended to the oxidation of other polyols/sugars to formic acid with excellent catalytic performance.

CeO2 Frustrated Lewis Pairs Improving CO2 and CH3OH Conversion to Monomethylcarbonate

Frustrated Lewis pairs (FLPs), discovered in the last few decades for homogeneous catalysts and in the last few years also for heterogeneous catalysts, are stimulating the scientific community's interest for their potential in small-molecule activation. Nevertheless, how an FLP activates stable molecules such as CO₂ is still undefined. Through a careful spectroscopic study, we here report the formation of FLPs over a highly defective CeO₂ sample prepared by microwave-assisted synthesis. Carbon dioxide activation over FLP is shown to occur through a bidentate carbonate bridging the FLP and implying a Ce³⁺-to-CO₂ charge transfer, thus enhancing its activation. Carbon dioxide reaction with methanol to form monomethylcarbonate is here employed to demonstrate active roles of FLP and, eventually, to propose a reaction mechanism clarifying the role of Ce³⁺ and oxygen vacancies.