Lewis Acid-base Pairs Research Articles

Constructing Ru-Co2P Lewis Acid-Base Pairs to Prompt Hydrogen Evolution Reaction in Alkaline Seawater Electrolyte.

Seawater electrolysis is an ideal approach to generating green hydrogen. Nevertheless, the sluggish kinetics of water dissociation and the detrimental chlorine chemistry environment are serious obstructions for industrial applications. Herein, constructing unique (Co) Lewis acid and (Ru-P) base pair sites in Ru-Co2P decorated on nitrogen and phosphorus co-doped carbon (Ru-Co2P/NPC) significantly optimizes the energy barrier of water dissociation and enhances the anti-corrosive ability for alkaline seawater splitting. As expected, the optimal Ru-Co2P/NPC-2 exhibits exceptional hydrogen evolution reaction (HER) performances with overpotentials as low as 22.0 and 26.0mV to derive 10 mAcm-2 and operate steadily (@ 50 mAcm-2) over 30 h in alkaline and alkaline seawater electrolytes. The experimental and theoretical results elucidate that Co acting as Lewis acid sites prompts the water adsorption and breakage of the H─O bond, whereas Ru-P as Lewis base sites facilitates the hydrogen desorption in alkaline media. Furthermore, modulated chemical microenvironments can be beneficial to hinder chloride corrosion on the active sites of catalysts. This work sheds light on the rational construction of a highly efficient electrocatalyst for alkaline HER in seawater.

Interface Synergy of Exposed Oxygen Vacancy and Pd Lewis Acid Sites Enabling Superior Cooperative Photoredox Synthesis.

Photo-driven cross-coupling of o-arylenediamines and alcohols has emerged as an alternative for the synthesis of bio-active benzimidazoles. However, tackling the key problem related to efficient adsorption and activation of both coupling partners over photocatalysts towards activity enhancement remains a challenge. Here, we demonstrate an efficient interface synergy strategy by coupling exposed oxygen vacancies (VO) and Pd Lewis acid sites for benzimidazole and hydrogen (H2) coproduction over Pd-loaded TiO2 nanospheres with the highest photoredox activity compared to previous works so far. The results show that the introduction of VO optimizes the energy band structure and supplies coordinatively unsaturated sites for adsorbing and activating ethanol molecules, affording acetaldehyde active intermediates. Pd acts as a Lewis acid site, enhancing the adsorption of alkaline amine molecules via Lewis acid-base pair interactions and driving the condensation process. Furthermore, VO and Pd synergistically promote interfacial charge transfer and separation. This work offers new insightful guidance for the rational design of semiconductor-based photocatalysts with interface synergy at the molecular level towards the high-performance coproduction of renewable fuels and value-added feedstocks.

Metal-organic frameworks Derived frustrated Lewis acid-base pairs accelerate ion dynamics to dendrite-free solid-state lithium batteries

The Poly(ethylene oxide) (PEO)-based polymer electrolytes exhibit the drawbacks of high crystallinity and low ionic conductivity (<10−5 S m−1), which significantly restrict their application in solid-state lithium metal batteries. This study presents the bismuth metal-organic frameworks (MOFs) as a PEO-based electrolyte filler, incorporating frustrated Lewis acid-base pairs, which is formed in-situ through the coordination of ellagic acid (EA) and bismuth ions (Bi3+). The simultaneous presence of Lewis acids (unsaturated Bi3+) and bases (free nitrate, NO3−) in the MOFs, which effectively transfers and transports the lithium ions through the synergistic interaction based on the polymer matrix and the lithium salts, resulting in the high durable solid-state lithium batteries. Meanwhile, NO3− can further promote the dissociation of lithium ion (Li+) and the formation of inorganic solid electrolyte interfaces (SEIs) with lithium metal, which is conducive to the dynamic repair of SEIs. Characterizations and calculations show that Bi-MOFs promote the increase of composite ionic conductivity (6.4 × 10−4 S cm−1, 60 °C) and lithium transference number (0.52, 60 °C). At a current density of 0.4 mA cm−2, the assembled Li–Li symmetric battery can be continuously cycled for more than 500 h. This strategy opens a new window for improvement of solid-state electrolyte performance.

Facile generation of unsaturated-coordinated and atomically-dispersed hafnium active sites for the highly efficient catalytic transfer hydrogenation of levulinic acid

The sluggish kinetic of the hydrogen transfer reaction pose a significant challenge in developing efficient catalytic transfer hydrogenation (CTH) system for upgrading biomass-derived platform molecules. In this contribution, for the first time, hafnium (Hf) species have been found to coordinate with the hydroxyl groups on halloysite nanotubes surface to construct a single-atom Hf catalyst (Hf@HNTs) with unsaturated-coordinated structure at room temperature. Especially, the Hf(1.7)@HNTs delivered an impressive catalytic performance for the CTH of levulinic acid (LvA) to gamma-valerolactone (GVL) with high turn-over frequency (TOF) of 43.1 h−1 at 160 °C, considerably exceeding that of coordination-saturated HfO2 and state-of-art Hf-based catalysts. Experimental and density functional theory (DFT) studies revealed that Hf(1.7)@HNTs possessed unsaturated-coordinated and atomically-dispersed Hf-O Lewis acid-base pairs, which favored the adsorption and activation of LvA. Moreover, DFT calculations explicitly demonstrated that the energy barriers for the hydrogen transfer between the LvA and hydrogen donor were significantly reduced on the Hf(1.7)@HNTs than that of HfO2.

Conversion of Carbon Dioxide into a Series of CBxOy- Compounds Mediated by LaB3,4O2- Anions: Synergy of the Electron Transfer and Lewis Pair Mechanisms to Construct B-C Bonds.

Converting CO2 into value-added products containing B-C bonds is a great challenge, especially for multiple B-C bonds, which are versatile building blocks for organoborane chemistry. In the condensed phase, the B-C bond is typically formed through transition metal-catalyzed direct borylation of hydrocarbons via C-H bond activation or transition metal-catalyzed insertion of carbenes into B-H bonds. However, excessive amounts of powerful boryl reagents are required, and products containing B-C bonds are complex. Herein, a novel method to construct multiple B-C bonds at room temperature is proposed by the gas-phase reactions of CO2 with LaBmOn- (m = 1-4, n = 1 or 2). Mass spectrometry and density functional theory calculations are applied to investigate these reactions, and a series of new compounds, CB2O2-, CB3O3-, and CB3O2-, which possess B-C bonds, are generated in the reactions of LaB3,4O2- with CO2. When the number of B atoms in the clusters is reduced to 2 or 1, there is only CO-releasing channel, and no CBxOy- compounds are released. Two major factors are responsible for this quite intriguing reactivity: (1) Synergy of electron transfer and boron-boron Lewis acid-base pair mechanisms facilitates the rupture of C═O double bond in CO2. (2) The boron sites in the clusters can efficiently capture the newly formed CO units in the course of reactions, favoring the formation of B-C bonds. This finding may provide fundamental insights into the CO2 transformation driven by clusters containing lanthanide atoms and how to efficiently build B-C bonds under room temperature.

CO2 derived ABA triblock all-polycarbonate thermoplastic elastomer with ultra-high elastic recovery

Although triblock polycarbonate thermoplastic elastomers (TPEs) have recently attracted great interests due to their biodegradability, insufficient attentions have been paid to improving the elastomeric properties. Through a tandem reaction strategy involving CO2 / allyl glycidyl ether (AGE) / cyclohexene oxide (CHO), poly(cyclohexene carbonate)-b-poly(allyl glycidyl ether carbonate)-b-poly(cyclohexene carbonate) (PCAC) is successfully synthesized using a metal-free Lewis acid-base pair catalyst. The synthesized PCACs are pure well-defined ABA triblock all-polycarbonate, which is supported by 1H NMR, gel permeation chromatography (GPC), and diffusion-ordered spectroscopy (DOSY). A simple modification by grafting alkylthiol chains to PCAC results in excellent TPEs named PCAC-g-S-CaH2a+1 (PCASaC). The synthesized TPEs are characterized by atomic force microscopy (AFM), thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and mechanical test. They demonstrate a semi-network and semi-domain phase separation structure, wide service temperature range, good strength, high elongation, and extremely high elastic recovery properties. This low-cost, biodegradable, high-performance TPE shows great potential for applications in biomedical, wearable products, sports equipment, and other fields.

Formal Decarbonylation of 1,2-Diketones Enabled by Synergistic Catalysis of Lewis Acid–Base Pairs and Redox Properties in CeO2

Formal Decarbonylation of 1,2-Diketones Enabled by Synergistic Catalysis of Lewis Acid–Base Pairs and Redox Properties in CeO₂

Phosphorus-modulated surface active center reconstruction in cerium oxide for polyols conversion into carbonates

Ionic liquids (ILs) can effectively regulate the surface morphology and acid-base sites of metal oxides, which is of great significance in the preparation of metal oxide nanomaterials. Here, cerium oxide (CeO2) was prepared in phosphonium-based ILs and P-doped CeO2 materials were obtained by doping phosphorous (P) on the surface of CeO2. Moreover, the yield and selectivity for ethylene carbonate (EC) synthesis catalyzed by CeO2 catalyst prepared were 77.26 % and 95.99 % respectively. The results indicated that an appropriate content of P could generate both Lewis acidic and basic sites related to P on the catalyst surface, and P-mediated frustrated Lewis acid-base pairs (FLPs) composed of P-OH as the basic center and Ce3+ as the acidic center was constructed. This work provides a new strategy for preparing novel CeO2 catalysts and regulating acid-base sites on the surface of that.

Supported LaCoO3 perovskite-like oxides for N2O decomposition: The key role of the support nature and LaCoO3 content

In this work a detailed comparison of the N2O decomposition catalytic performance of LaCoO3 perovskite-like mixed oxides supported over different commercial materials was conducted. Zirconia-, silica- and γ-alumina-based supports were studied. Zirconia-based supports turned out to be the most applicable because of the formation of the pure LaCoO3 perovskite phase on their surface. Among these supports, ZrO2-La revealed to possess the best activity owing to the highest Co2+/Co3+ (0.82) and Oads./OL (0.67) ratios on its surface. The raw of activities was as follows: LaCoO3(20 %)/ZrO2-La > LaCoO3(20 %)/ZrO2 > LaCoO3(20 %)/ZrO2-W. When the LaCoO3 content in LaCoO3/ZrO2-La was 20 wt%, the maximum of activity was observed – 94.78 mmol(N2O)/[g(cat.)·h] at 450 °C. This fact was in accordance with the highest Co2+/Co3+ (0.82) and Oads./OL (0.67) ratios at the 20 wt% LaCoO3 content. Coordinatively unsaturated Co2+, forming Lewis acid-base pairs, were proposed to be the active sites of the zirconia-based LaCoO3 catalysts in the N2O decomposition.

Effect of hydrogen sources toward the CO2 photoreduction on boron decorated crystalline carbon nitride

Photocatalytic CO2 conversion to industrial fuels is considered an effective measure to solve energy and environmental problems. Presently, Catalysts for CO2 reduction reaction (CO2RR) are mostly confined to metal-based materials, but non-metal materials are less explored. We decorate the highly crystalline carbon nitride, i.e., poly(triazine) imides (PTI), with non-metallic boron (B) to obtain two B/PTI catalysts: Bi/PTI with B being deposited into the six-fold cavity of the PTI, and Bs/PTI with B substituting for C in PTI. For CO2RR, Bi/PTI follows a quasi Mars-van Krevelen process, but the high exposure of Bi results in an overly strong interaction with intermediates, inhibiting the reactivity. In contrast, Bs/PTI enhances the binding with intermediates by introducing Lewis acid-base pairs (B-N), which reduce the ring conjugation effect and induce the enrichment of electrons at the pyridine N. Hence, CO2 reduction with the adsorbed H* (Ha) hydrogenation mechanism in Bs/PTI has a significant reactivity.

C2H2 selective hydrogenation over metal-doped CeO2 catalysts: Unraveling the role of metal and surface frustrated Lewis acid-base pair in tuning catalytic performance

Doping the second metal into CeO2 is used as a generally regarded strategy to promote C2H2 selective hydrogenation. This work employs DFT calculations and microkinetic modeling to explore the performance of CeO2 doped with different Cu, Ni, Pd, Pt, or Co atom towards C2H2 selective hydrogenation. The results show that the doped metal not only promotes the formation of surface oxygen-vacancy, but also generate different types of FLPs with surface O atom. FLPs promote H2 heterolytic dissociation to produce Ce-H/M-H and O-H species. Different forms of surface H species affect the performance of C2H2 selective hydrogenation. C2H4 selectivity follows a U-shaped dependence on surface Ce atom charge transfer amount. The screened catalyst Co/CeO2 presents excellent C2H4 production activity and selectivity, which could well prevent the generation of green oil. This work provides new insights for designing highly efficient metal-doped CeO2 catalysts by tuning the doped metal type.

Advances in Catalysts for Urea Electrosynthesis Utilizing CO2 and Nitrogenous Materials: A Mechanistic Perspective.

Electrocatalytic urea synthesis from CO2 and nitrogenous substances represents an essential advance for the chemical industry, enabling the efficient utilization of resources and promoting sustainable development. However, the development of electrocatalytic urea synthesis has been severely limited by weak chemisorption, poor activation and difficulties in C-N coupling reactions. In this review, catalysts and corresponding reaction mechanisms in the emerging fields of bimetallic catalysts, MXenes, frustrated Lewis acid-base pairs and heterostructures are summarized in terms of the two central mechanisms of molecule-catalyst interactions as well as chemical bond cleavage and directional coupling, which provide new perspectives for improving the efficiency of electrocatalytic synthesis of urea. This review provides valuable insights to elucidate potential electrocatalytic mechanisms.

Oxygen-Vacancy-Mediated Large Binding Energy Exciton Dissociation in Nb3O7(OH) Nanorods with High Electron Mobility for CO2 Photoreduction.

Despite the excellent performance of Nb3O7(OH) in dye-sensitized solar cells and catalysis, its charge separation, transport, and structural properties remain poorly understood. Herein, the Nb3O7(OH) nanorods were prepared, and their structural characteristics, optoelectronic properties, and carrier mobility were also analyzed and investigated through a series of complex characterizations. Theoretical prediction suggested that the exciton binding energy of Nb3O7(OH) could be as high as 100.49 meV. The temperature-dependent photoluminescence (PL) of Nb3O7(OH) nanorods revealed two activation energies, and a higher proportion of long-lived components observed in the photoluminescence decay indicated effective electron trapping. That is, two energy states were present, hindering photogenerated charge recombination and promoting photocatalytic action. Current-voltage characteristics of the Nb3O7(OH) nanorod film were analyzed, revealing an ultrahigh carrier mobility of ∼310 cm2/V·s, ensuring fast and efficient electron transfer. Furthermore, Nb3O7(OH) nanorods were employed to reduce CO2, resulting in the effective production of CO and CH4. Overall, considering the presence of hydroxyl pairs on the surface of Nb3O7(OH), which facilitate the formation of the frustrated Lewis acid-base pairs and the activation of CO2, together with its effective electron trapping and charge transport, give Nb3O7(OH) nanorods a promising potential for CO2 reduction.

Zirconium induced surfaces frustrated Lewis acid-base pairs for BiOBr boosting CO2 photoreduction

Conversion of CO2 to carbon-based fuels via photocatalytic reduction, as a prospective approach, could alleviate energy shortages and environmental problems. However, the adsorption and activation of CO2 in the process of photocatalytic CO2 reduction are still great challenge. Herein, Zr isomorphous substituted BiOBr catalyst with surface frustrated Lewis acid-base pairs (SFLPs) are formed by a convenient chemical method. The photocatalytic activity of CO2 reduction for optimal Zr-BiOBr is significantly improved, with CO yield of 185.7 μmol·g−1·h−1 and CH4 of 0.7 μmol·g−1·h−1, being 9.2 - fold and 3.2 - fold higher than that of original BiOBr, respectively. It is found that zirconium is considered as Lewis acid site and lattice oxygen as Lewis base site, which could effectively boost the adsorption and activiation of CO2 molecules. This work not only demonstrates that construction of SFLPs for catalyst could be taken as an effective tactics for CO2 adsorption and activation, but also suggests a possible photocatalytic mechanism in depth.

Efficient nitrite-to-ammonia electroreduction over Zr-Ni frustrated Lewis acid-base pairs

Efficient nitrite-to-ammonia electroreduction over Zr-Ni frustrated Lewis acid-base pairs

A DFT study on the formation mechanism of side product 1,2-propanediol in the hydrogenation of dimethyl oxalate over copper catalyst

The costly separation of 1,2-propanediol (1,2-PDO), an unavoidable byproduct in the hydrogenation of dimethyl oxalate (DMO), significantly hampers the economic viability of coal-to-ethylene glycol (EG) technology. To address this challenge, the formation mechanism of the side product 1,2-PDO on the Cu(111) and Cu2O(111) surfaces during DMO hydrogenation was investigated, which focused on the active sites of copper catalyst and the dominant pathway through density functional theory calculation. The thermodynamics of each elementary step and the adsorption behavior of various species involved in the reaction network along with the local density of states and charge density difference were systematically analyzed. The results indicate that 1,2-PDO is generated more favorably on the Cu2O(111) surface than that on the Cu(111) surface, owing to the Lewis acid-base pairs, i.e. Cu+ us and O– suf sites, present on the Cu2O(111) surface, which strengthens the binding of reactants, products, and reaction intermediates to the substrate. EG reacts primarily with methanol (MeOH) to form 1,2-PDO through Guerbet alcohol condensation reaction through three consecutive steps: alcohol dehydrogenation, aldol condensation, and unsaturated aldehyde hydrogenation. The O– suf sites promote the dehydrogenation of alcohols into aldehydes, the generation of enolates during aldol condensation and the hydrogenation of unsaturated aldehydes, while the Cu+ us sites are responsible for the C–C coupling reaction. These findings may shed light on the mechanism of 1,2-PDO formation over Cu catalyst and provide fundamental knowledge for the development of more efficient catalysts and process optimization.

A Chiral B-N Adduct as a New Frontier in Ferroelectrics and Piezoelectric Energy Harvesting.

Within the burgeoning field of electronic materials, B-N Lewis acid-base pairs, distinguished by their partial charge distribution across boron and nitrogen centers, represent an underexplored class with significant potential. These materials exhibit inherent dipoles and are excellent candidates for ferroelectricity. However, the challenge lies in achieving the optimal combination of hard-soft acid-base pairs to yield B-N adducts with stable dipoles. Herein, we present an enantiomeric pair of B-N adducts [R/SC6H5CH(CH3)NH2BF3] (R/SMBA-BF3) crystallizing in the polar monoclinic P21 space group. The ferroelectric measurements on RMBA-BF3 gave a rectangular P-E hysteresis loop with a remnant polarization of 7.65 μC cm-2, a value that aligns with the polarization derived from the extensive density-functional theory computations. The PFM studies on the drop-casted film of RMBA-BF3 further corroborate the existence of ferroelectric domains, displaying characteristic amplitude-bias butterfly and phase-bias hysteresis loops. The piezoelectric nature of the RMBA-BF3 was confirmed by its direct piezoelectric coefficient (d33) value of 3.5 pC N-1 for its pellet. The piezoelectric energy harvesting applications on the sandwich devices fabricated from the as-made crystals of RMBA-BF3 gave an open circuit voltage (VPP) of 6.2 V. This work thus underscores the untapped potential of B-N adducts in the field of piezoelectric energy harvesting.

Spectroscopic Characterization of Thermal Methane Activation by Lewis-Acid-Base Pair in a Gas-Phase Metal Nitride Anion Ta2N3.

Activation and transformation of methane is one of the "holy grails" in catalysis. Understanding the nature of active sites and mechanistic details via spectroscopic characterization of the reactive sites and key intermediates is of great challenge but crucial for the development of novel strategies for methane transformation. Herein, by employing photoelectron velocity-map imaging (PEVMI) spectroscopy in conjunction with quantum chemistry calculations, the Lewis acid-base pair (LABP) of [Taδ+-Nδ-] unit in Ta2N3 - acting as an active center to accomplish the heterolytic cleavage of C-H bond in CH4 has been confirmed by direct characterization of the reactant ion Ta2N3 - and the CH4-adduct intermediate Ta2N3CH4 -. Two active vibrational modes for the reactant (Ta2N3 -) and four active vibrational modes for the intermediate (Ta2N3CH4 -) were observed from the vibrationally resolved PEVMI spectra, which unequivocally determined the structure of Ta2N3 - and Ta2N3CH4 -. Upon heating, the LABP intermediate (Ta2N3CH4 -) containing the NH and Ta-CH3 unit can undergo the processes of C-N coupling and dehydrogenation to form the product with an adsorbed HCN molecule.

Local In-O-Pd Lewis acid-base pair boosting CO2 selective hydrogenation to methanol

CO2 hydrogenation into valuable chemicals is industrially essential but very challenging since CO2 is chemically inert and the selectivity is difficult to control. Here, we design and construct In2O3 supported Pd single atoms (Pd1/In2O3 SAC) to boost the methanol yield (254.8 gmethanol·gPd−1·h−1) and selectivity (99.4 %) via the Lewis acid-base pair, which activates the CO2 and forms the intermediate species of formate (HCOO*). The comprehensive experimental and theoretical results confirm that the local Lewis acid-base pair is composed of the isolated Pd atom coupling with the adjacent O and In atoms. The space–time yield (STY) of methanol over Pd1/In2O3 SAC is around 1.7 times higher than the best reported catalysts under comparable conditions. The strategy of constructing local Lewis acid-base pairs with single-atom site and metal oxides reported in this work opens new avenues to develop highly selective catalysts for CO2 utilization.

MOFs-derived (Fe3O4/Fe2O3)OH@C-X in-situ form frustrated Lewis acid-base pairs for visible-light-driven photocatalytic CO2 reduction

Frustrated Lewis pairs (FLPs) have demonstrated their capacity to capture and react with CO2, presenting a novel method for CO2 reduction. Despite this, their practical application remains limited due to a complex preparation process, poor stability, and regeneration challenges. We address these issues in this study by pyrolyzing a metal-organic framework (MOF) to form in-situ FLPs on an iron oxide surface. The resulting (Fe3O4/Fe2O3)OH@C-400 composite exhibits a significantly improved CO2 reduction rate of 173.3 μmol g−1 h−1, which is approximately 13.4 times higher than that of Fe2O3 and 10.9 times higher than that of Fe3O4. Both theoretical and experimental findings confirm that the creation of heterostructured hollow spheres and in-situ FLPs enhances visible light absorption, improves the separation and transfer of photogenerated carriers, and increases the photocatalytic efficiency for CO2 reduction. The H/D kinetic isotope effect suggests that water plays a crucial role in the limiting step of CO2 photoreduction. In-situ FTIR results corroborate the formation of COOH* as a critical intermediate in photocatalytic CO2 reduction over (Fe3O4/Fe2O3)OH@C-X. This research provides a novel insight into catalyst material design and mechanism research for photocatalytic CO2 reduction.