Electron Pair Research Articles

Regulation of Exciton Effects in Functionalized Conjugated Polymers by B‐N Lewis Pairs for Visible‐Light Photocatalysis

Strong excitonic effects are common in organic conjugated polymer semiconductors, severely hindering the generation of free charge carriers for conducting photocatalysis. Therefore, exploring new channels to modulate exciton dissociation in polymers is far‐reaching in facilitating photocatalysis. A series of B‐N Lewis pair functionalized conjugated polymers have been developed to minimize exciton effects by modulating charge transfer pathways. Theoretical studies have shown that introducing B‐N Lewis pairs can dramatically increase the distance of charge transfer (D index) and the amount of electron transfer and reduce the Coulomb attraction energy (EC), which contributes to breaking the equilibrium of the coexistence of excitons and charge carriers. Further experimental results show that the singlet excitons are efficiently dissociated into more free‐charge carriers under photoexcitation to participate in surface reactions. The optimized polymer PyPBM shows an exponential increase in photocatalytic hydrogen and hydrogen peroxide production performance by visible light illumination.

Regulation of Exciton Effects in Functionalized Conjugated Polymers by B-N Lewis Pairs for Visible-Light Photocatalysis.

Strong excitonic effects are common in organic conjugated polymer semiconductors, severely hindering the generation of free charge carriers for conducting photocatalysis. Therefore, exploring new channels to modulate exciton dissociation in polymers is far-reaching in facilitating photocatalysis. A series of B-N Lewis pair functionalized conjugated polymers have been developed to minimize exciton effects by modulating charge transfer pathways. Theoretical studies have shown that introducing B-N Lewis pairs can dramatically increase the distance of charge transfer (D index) and the amount of electron transfer and reduce the Coulomb attraction energy (EC), which contributes to breaking the equilibrium of the coexistence of excitons and charge carriers. Further experimental results show that the singlet excitons are efficiently dissociated into more free-charge carriers under photoexcitation to participate in surface reactions. The optimized polymer PyPBM shows an exponential increase in photocatalytic hydrogen and hydrogen peroxide production performance by visible light illumination.

Proximity‐Induced Unconventional Superconducting Quantum Oscillation in WTe2/NbSe2 Heterostructures

AbstractThe electron pairing mechanisms in topological superconductors are pivotal for understanding the emergent topology‐related quantum states and play key roles in condensed matter physics. Theoretically, the quantization of magnetic flux in nano‐hole arrays within topological superconductors can be studied for understanding the Bogoliubov quasiparticles via the Little–Parks oscillation. However, experimental evidence of the quasiparticle states in such structures of topological superconductors remains elusive. Here, the unconventional superconducting quantum oscillation phenomena of the proximity‐induced 2D topological superconductivity (TSC) is demonstrated in a nano‐hole array of WTe2/NbSe2 heterojunction. The unconventional oscillation period in WTe2 is substantially smaller than that in the s‐wave superconductor NbSe2 (corresponds to Cooper pairs), implying the probable presence of novel quasiparticle states associated with TSC. Interestingly, such phenomena of multi‐charge flux quanta might be related to the multi‐particle bound states of TSC. These observations provide a new approach for exploring the unconventional superconducting quantum states in topological superconductors.

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.

Computational design for enantioselective CO2 capture: asymmetric frustrated Lewis pairs in epoxide transformations.

Carbon capture and utilisation (CCU) technologies offer a compelling strategy to mitigate rising atmospheric carbon dioxide levels. Despite extensive research on the CO2 insertion into epoxides to form cyclic carbonates, the stereochemical implications of this reaction have been largely overlooked, despite the prevalence of racemic epoxide solutions. This study introduces an in silico approach to design asymmetric frustrated Lewis pairs (FLPs) aimed at controlling reaction stereochemistry. Four FLP scaffolds, incorporating diverse Lewis acids (LA), Lewis bases (LB), and substituents, were assessed via volcano plot analysis to identify the most promising catalysts. By strategically modifying LB substituents to induce asymmetry, a stereoselective catalytic scaffold was developed, favouring one enantiomer from both epoxide enantiomers. This work advances the in silico design of FLPs, highlighting their potential as asymmetric CCU catalysts with implications for optimising catalyst efficiency and selectivity in sustainable chemistry applications.

Vanadium(V/IV) Oxido Complexes: Potential as Bases in Frustrated Lewis Pairs

AbstractFrustrated Lewis Pairs (FLP) have found exciting access in catalysis and small molecule activation. Here, we describe the potential of two vanadium(V) oxido complexes with monoanionic bidentate N,O donors, [VOCl(LCF3)2] (1 a), [VOCl(LH)2] (1 b) as bases in FLPs. Upon reaction of 1 a with the Lewis acid B(C6F5)3 the FLP [VOCl(LCF3)2]/B(C6F5)3 (1 a/B(C6F5)3) was observed. Addition of Ph3SiH led to the reduction of VV to VIV under formation of the adduct [V{OB(C6F5)3}(LCF3)2] (2 a) while FLP reactivity was not observed. Dissolving 2 a in CH3CN leads to the VIV oxido complex, [VO(LCF3)2] (3 a). In contrast, when 1 b was reacted with B(C6F5)3, a VIV oxido complex [VO(LH)2] (3 b) was obtained. Upon addition of B(C6F5)3 to 3 b no reaction leading to the expected adduct such as 2 a could be observed. Only few crystals deriving from a disproportion reaction could be identified as an adduct dimer [V{OB(C6F5)3}LH(μ‐O)]2. While FLP reactivity could not be found yet with the described systems, the redox labile nature and versatility of the metal complexes are demonstrated.

A colorimetric platform using highly active Prussian blue composite nanocubes for the rapid determination of ascorbic acid and acid phosphatase.

Cobalt-doped Prussian blue composite nanocubes (Co-PB NCs) were synthesized, which can quickly convert O2 to O2•- and 1O2. Due to the presence of cobalt and iron transition metal redox electron pairs, Co-PB NCs with high oxidase mimetic activity can rapidly oxidize the substrate 3,3',5,5'-tetramethylbenzidine (TMB) to produce blue products (ox-TMB) without the assistance of unstable H2O2. Using ascorbic acid-2-phosphate trisodium salt (AAP) as a substrate, it can be converted to reduced ascorbic acid (AA) under acid phosphatase (ACP) hydrolysis, resulting in suppression of TMB oxidation. Therefore, an enzyme cascade signal amplification strategy for rapid colorimetric detection of AA/ACP was developed based on the high-efficiency oxidase-like activity of Co-PB NCs combined with the hydrolysis effect of ACP. The color changes at low concentrations of AA and ACP could be observed by the naked eye, and the detection limits of AA and ACP were 1.67μM and 0.0266 U/L, respectively. The developed colorimetric method was applied to the determination of AA in beverages and ACP in human serum, and the RSDs were less than 3%, showing good reproducibility. This work provides a promising strategy for the use of metal-doped Prussian blue composite material for the construction of rapid colorimetric sensing platforms that avoid the use of unstable hydrogen peroxide.

The facile preparation of polydopamine-modified sepiolite and its adsorption properties and microscopic mechanism for cadmium ion

Natural sepiolite (SEP) has the characteristics of cation exchange, abundant reserves, low cost, and environmental friendliness, but its adsorption capacity for heavy metal pollutants is limited. Because polydopamine (PDA) molecules contain rich functional groups such as phenolic and amino groups, in the present work, dopamine and natural sepiolite were utilized as raw materials to prepare polydopamine-modified sepiolite composite (SEP/PDA) by simple co-precipitation method. According to Langmuir isotherm model, the maximum adsorption capacity of SEP/PDA for Cd2+ can reach 203.21 mg/g at 298 K. At the initial concentration of 100 mg/L, the adsorption capacity was 2.9 times that of natural sepiolite. The composite material has good reusability and anti-cationic interference performance and has 100 % removal ability of low concentration Cd2+ in actual electroplating wastewater. Density Functional Theory (DFT) calculations were performed to obtain the electronic structure information. To elucidate the microscopic mechanism, molecular surface analyses, Interaction Region Indicator (IRI), Atom In Molecules (AIM) theory, Bond Order Density (BOD), and Electron Localization Function (ELF) were conducted. These analyses revealed that the amino nitrogen and phenolic oxygen atoms in the dopamine molecules donate lone pair electrons to coordinate with cadmium ions. Polydopamine, which possesses multiple oxidation states, contains catechol, quinone, and indole or a lesser extend pyrrole groups that can complex with cadmium ions, resulting in the formation of a surface complex. This coordination significantly enhances the adsorption properties of the SEP/PDA composite.

Monovalent nickel ion as ionization probe in matrix-assisted laser desorption/ionization mass spectrometry

We have developed NiO/HM20, a matrix composed of NiO nanoparticles (NiO) loaded on zeolite surface, for matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). By photoexcitation, monovalent nickel ion (Ni+) was dominantly observed with high intensity. The mechanism of Ni+ production was studied by picosecond time-resolved emission spectroscopy. By loading NiO on the zeolite surface, a new relaxation pathway to other electronic excited states was observed, which increased the lifetime of electron–hole pairs and promoted the reduction of nickel. The long-lived charge-separated electronic excited state corresponding to the large polarization of NiO was confirmed by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction spectroscopy (XRD). The correlation between the Auger parameter related to the polarization energy and the Ni+ peak intensity in the mass spectrum was confirmed. By applying the developed NiO/HM20 matrix to the MS measurement of small molecules, we found that molecules were ionized through complex formation with Ni+ using the coordination of lone electron pairs or π-electrons in the analyte molecules.

DNA: Novel Crystallization Regulator for Solid Polymer Electrolytes in High-Performance Lithium-Ion Batteries.

In this work, we designed a novel polyvinylidene fluoride (PVDF)@DNA solid polymer electrolyte, wherein DNA, as a plasticizer-like additive, reduced the crystallinity of the solid polymer electrolyte and improved its ionic conductivity. At the same time, due to its Lewis acid effect, DNA promotes the dissociation of lithium salts when interacting with lithium salt anions and can also fix the anions, creating more free lithium ions in the electrolyte and thus improving its ionic conductivity. However, owing to hydrogen bonding between DNA and PVDF, excess DNA occupies the lone pairs of electrons of the fluorine atoms on the PVDF molecular chains, affecting the conduction of lithium ions and the conductivity of the solid electrolyte. Hence, in this study, we investigated the effects of adding different DNA amounts to solid polymer electrolytes. The results show that 1% DNA addition resulted in the best improvement in the electrochemical performance of the electrolyte, demonstrating a high ionic conductivity of 3.74 × 10-5 S/cm (25 °C). The initial capacity reached 120 mAh/g; moreover, after 500 cycles, the all-solid-state batteries exhibited a capacity retention of approximately 71%, showing an outstanding cycling performance.

Frustrated Lewis Pair-Promoted Organocatalytic Transformation of Hydrosilanes into Silanols with Water Oxidant.

Owing to their unique properties, the silanols have attracted intense attention but remain challenging to prepare from the organocatalytic oxidation of hydrosilanes using H2O as a green oxidant. Herein, we employ a frustrated Lewis pair (FLP) to successfully suppress the formation of undesired siloxanes and produce silanols in high to excellent yields in the presence of H2O. Mechanistic studies suggest that the reaction is initiated with the activation of FLP by H2O rather than by silanes and goes through a concerted SN2 mechanism. More importantly, the combination of the FLP-catalyzed oxidation of hydrosilanes with B(C6F5)3-catalyzed dehydrogenation enables us to realize the precise synthesis of sequence-controlled oligosiloxanes. This method exhibits a broad substrate scope and can be easily scaled up, thus exhibiting promising application potentials in the precision synthesis of silicon-containing polymer materials.

Complexes of a Frustrated Lewis Pair-Supported P(-1) Ligand.

Several complexes of the intramolecular frustrated Lewis pair (FLP)-supported P(-1) ligand [iPr2P(C6H4)BCy2{P}]- are presented (Cy=cyclohexyl). Chief among these is the first example of a monomeric zinc bis(phosphido) complex, which was synthesized as a potential precursor for the solution-phase deposition of Zn3P2. While this goal was ultimately unsuccessful, the Zn(II) complex acts as a convenient springboard to other metal phosphide species via transmetallation: affording a tellurium bis(phosphido) complex and a formal adduct of the phosphorus subhalide PPCl2. Trapping experiments show that the PPCl2 adduct can also be prepared directly through the in situ reduction of PCl3 in the presence of an intramolecular FLP ligand. Lastly, we report a formal η2-phosphaborene complex of cobalt(-1) which is isoelectronic to olefin complexes, and explore its bonding via density functional theory (DFT) computations.

Radiation-Synthesized Metal-Organic Frameworks with Ligand-Induced Lewis Pairs for Selective CO2 Electroreduction.

The electrochemical activation of inert CO2 molecules through C─C coupling reactions under ambient conditions remains a significant challenge but holds great promise for sustainable development and the reduction of CO2 emission. Lewis pairs can capture and react with CO2, offering a novel strategy for the electrosynthesis of high-value-added C2 products. Herein, an electron-beam irradiation strategy is presented for rapidly synthesizing a metal-organic framework (MOF) with well-defined Lewis pairs (i.e., Cu- Npyridinic). The synthesized MOFs exhibit a total C2 product faradic efficiency of 70.0% at -0.88V versus RHE. In situ attenuated total reflection Fourier transform infrared and Raman spectra reveal that the electron-deficient Lewis acidic Cu sites and electron-rich Lewis basic pyridinic N sites in the ligand facilitate the targeted chemisorption, activation, and conversion of CO2 molecules. DFT calculations further elucidate the electronic interactions of key intermediates in the CO2 reduction reaction. The work not only advances Lewis pair-site MOFs as a new platform for CO2 electrochemical conversion, but also provides pioneering insights into the underlying mechanisms of electron-beam irradiated synthesis of advanced nanomaterials.

2,2'-Bipyridyl-4,4'-Dicarboxylic Acid Modified Buried Interface of High-Performance Perovskite Solar Cells.

The regulation of interfaces remains a critical and challenging aspect in the pursuit of highly efficient and stable perovskite solar cells (PSCs). Here, 2,2'-bipyridyl-4,4'-dicarboxylic acid (HBPDC) is incorporated as an interfacial layer between SnO2 and perovskite layers in PSCs. The two carboxylic acid moieties on HBPDC bind to SnO2 through esterification, while its nitrogen atoms, possessing lone electron pairs, interact with uncoordinated lead (Pb2+) atoms through Lewis acid-base interactions. This dual functionality enables simultaneous passivation of surface defects on both the SnO2 and buried perovskite layers. In addition, the electron-deficient nature of HBPDC enhances interfacial energy band alignment and facilitates electron transfer from the perovskite to SnO2. Furthermore, the incorporation of HBPDC strengthens the interfacial adhesion, improving mechanical reliability. As a result, the PSCs exhibited an impressive power conversion efficiency (PCE) of 25.41% under standard AM 1.5G conditions, along with remarkable environmental stability.

2,2′‐Bipyridyl‐4,4′‐Dicarboxylic Acid Modified Buried Interface of High‐Performance Perovskite Solar Cells

The regulation of interfaces remains a critical and challenging aspect in the pursuit of highly efficient and stable perovskite solar cells (PSCs). Here, 2,2′‐bipyridyl‐4,4′‐dicarboxylic acid (HBPDC) is incorporated as an interfacial layer between SnO2 and perovskite layers in PSCs. The two carboxylic acid moieties on HBPDC bind to SnO2 through esterification, while its nitrogen atoms, possessing lone electron pairs, interact with uncoordinated lead (Pb2+) atoms through Lewis acid‐base interactions. This dual functionality enables simultaneous passivation of surface defects on both the SnO2 and buried perovskite layers. In addition, the electron‐deficient nature of HBPDC enhances interfacial energy band alignment and facilitates electron transfer from the perovskite to SnO2. Furthermore, the incorporation of HBPDC strengthens the interfacial adhesion, improving mechanical reliability. As a result, the PSCs exhibited an impressive power conversion efficiency (PCE) of 25.41% under standard AM 1.5G conditions, along with remarkable environmental stability.

Boosting HER performance by using plasma prepared N-doped CNTs to support Pt nanoparticles

Developing highly-efficient and stable Pt-based catalysts towards alkaline hydrogen evolution reaction (HER) offers a promising strategy for future renewable energy. In this work, radio-frequency (RF) cold plasma-prepared N-doped MWCNTs were adopted to support Pt nanoparticles (NPs) (Pt/NCNTs) via pretreating MWCNTs with RF nitrogen plasma and combining with traditional thermal reduction method. The as-synthesized Pt/NCNT featured an ultra-small size of Pt NPs (1.5 nm) and plentiful doped nitrogen, exhibiting ultra-low overpotential of 28 mV@10 mA cm−2 and ultra-high mass activity of 3.2 A mg Pt−1@100 mA in 1 M KOH solution, which are superior to those of commercial 20 wt% Pt/C catalyst. This is because RF plasma can realize fast, high-efficient and specific N-doping structure of MWCNTs. The lone electron pairs of N species (mainly pyri-N and pyrr-N) on MWCNTs surface transfer to the empty orbitals of Pt NPs, forming a strong coordination effect between Pt and nitrogen, thereby boosting the alkaline HER catalytic performance.

The Fischer‐lactonization‐driven mechanism for ultra‐efficient recycling of spent lithium‐ion batteries

Hydrometallurgy remains a major challenge to simplify its complex separation and precipitation processes for spent lithium‐ion batteries (LIBs). Herein, we propose a Fischer‐lactonisation‐driven mechanism for the cascade reaction of leaching and chelation of spent LIBs. Citric acid undergoes a two‐step dissociation of the carboxylic acid (‐COOH) and complexes with the leached metal ion, while the residual ‐COOH is attacked by H protons to form a protonated carboxyl ion (‐COO^‐). Subsequently, the lone pair of electrons in the hydroxyl of the same molecule attack the carbon atom in ‐COO^‐ to facilitate ester bonding, leading to the formation of a lactonized gel. The leaching rates of Li, Ni, Co and Mn are 99.3, 99.1, 99.5 and 99.2%, respectively. The regenerated monocrystalline LiNi0.5Co0.2Mn0.3O2 (NCM523) has a uniform particle size distribution and complete lamellar structure, with a capacity retention rate of 70.6% after 250 cycles at 0.5 C. The mechanism achieves a one‐step chelation reaction, and the energy consumption and carbon emissions are only 26% and 44%, respectively, of that of the conventional hydrometallurgical. The strategy achieves a double breakthrough in simplifying the process and improving environmental friendliness, offering a sustainable approach to the re‐utilization of spent LIBs.

Frustrated Lewis Pair Mediated f‐p‐d Orbital Coupling: Achieving Selective Seawater Oxidation and Breaking *OH and *OOH Scaling Relationship

The development of materials for hydrogen production via seawater electrolysis at high current densities plays a crucial role in producing renewable hydrogen energy. However, during the seawater electrolysis process, the anode inevitably undergoes chloride oxidation reaction (ClOR) due to Cl‐ adsorption, making the seawater electrolysis process difficult to sustain. Inspired by the selective permeability of cell membranes, we propose a biomimetic design of frustrated Lewis pairs (FLPs) layers. Combining experimental results and molecular dynamics simulations, it has been demonstrated that cerium dioxide layers with FLPs sites can decompose water molecules, capture hydroxyl anions, and repel chloride ions simultaneously. DFT theoretical analysis indicates that the FLP sites regulate the Ce 4f‐O 2p‐Ni 3d gradient orbital coupling, providing additional oxygen non‐bonding (ONB) to stabilize the Ni‐O bond and optimize the adsorption strength of intermediates, thereby breaking the *OH and *OOH scaling relationship. Assembled anion exchange membrane electrolyzers exhibit an efficiency of 95.7% at a current density of 0.1 A cm‐2 and can stably operate for 250 hours at a current density of 0.2 A cm‐2.

Frustrated Lewis Pair Mediated f-p-d Orbital Coupling: Achieving Selective Seawater Oxidation and Breaking *OH and *OOH Scaling Relationship.

The development of materials for hydrogen production via seawater electrolysis at high current densities plays a crucial role in producing renewable hydrogen energy. However, during the seawater electrolysis process, the anode inevitably undergoes chloride oxidation reaction (ClOR) due to Cl- adsorption, making the seawater electrolysis process difficult to sustain. Inspired by the selective permeability of cell membranes, we propose a biomimetic design of frustrated Lewis pairs (FLPs) layers. Combining experimental results and molecular dynamics simulations, it has been demonstrated that cerium dioxide layers with FLPs sites can decompose water molecules, capture hydroxyl anions, and repel chloride ions simultaneously. DFT theoretical analysis indicates that the FLP sites regulate the Ce 4f-O 2p-Ni 3d gradient orbital coupling, providing additional oxygen non-bonding (ONB) to stabilize the Ni-O bond and optimize the adsorption strength of intermediates, thereby breaking the *OH and *OOH scaling relationship. Assembled anion exchange membrane electrolyzers exhibit an efficiency of 95.7% at a current density of 0.1 A cm-2 and can stably operate for 250 hours at a current density of 0.2 A cm-2.

Electrochemically Gated Frustrated Lewis Pair Chemistry in Electric Double Layer.

The recent discovery of frustrated Lewis pairs (FLPs) during the activation of small molecules has inspired extensive research across the full span of chemical science. Owing to the nature of weak interactions, it is experimentally challenging to directly observe and modulate FLP at the molecular scale. Here we design a boron cluster anion building block (B10H82-) and organic amine cations ([NR4]+, R= -CH3, -C2H5) as the FLP to prove the feasibility of controlling their interaction in the electric double layer (EDL) via an electrochemical strategy. In situ single-molecule electrical measurements and Raman monitoring of B10H82--[NR4]+ FLP formed at the positively charged Au(111) electrode surface, in contrast to the free-standing B10H82- near or below the potential of zero charge (PZC). Furthermore, this FLP chemistry leads to a shift in the local density of states of boron clusters towards the EF for enhancing electron transport, providing a new prototype of a reversible single-cluster switch that digitally switches upon controlling FLP chemistry in the electric double layer.