Lewis Acid-base Interactions Research Articles

Nanosecond Metal-to-Ligand Charge-Transfer State in an Fe(II) Chromophore: Lifetime Enhancement via Nested Potentials.

Examples of Fe complexes with long-lived (≥1 ns) charge-transfer states are limited to pseudo-octahedral geometries with strong σ-donor chelates. Alternative strategies based on varying both coordination motifs and ligand donicity are highly desirable. Reported herein is an air-stable, tetragonal FeII complex, Fe(HMTI)(CN)2 (HMTI = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene), with a 1.25 ns metal-to-ligand charge-transfer (MLCT) lifetime. The structure has been determined, and the photophysical properties have been examined in a variety of solvents. The HMTI ligand is highly π-acidic due to low-lying π*(C═N), which enhances ΔFe via stabilizing t2g orbitals. The inflexible geometry of the macrocycle results in short Fe-N bonds, and density functional theory calculations show that this rigidity results in an unusual set of nested potential energy surfaces. Moreover, the lifetime and energy of the MLCT state depends strongly on the solvent environment. This dependence is caused by modulation of the axial ligand-field strength by Lewis acid-base interactions between the solvent and the cyano ligands. This work represents the first example of a long-lived charge transfer state in an FeII macrocyclic species.

Direct air capture (DAC) and sequestration of CO 2 : Dramatic effect of coordinated Cu(II) onto a chelating weak base ion exchanger

Direct air capture (DAC) is important for achieving net-zero greenhouse gas emissions by 2050. However, the ultradilute atmospheric CO2 concentration (~400 parts per million) poses a formidable hurdle for high CO2 capture capacities using sorption-desorption processes. Here, we present a Lewis acid-base interaction-derived hybrid sorbent with polyamine-Cu(II) complex enabling over 5.0 mol of CO2 capture/kg sorbent, nearly two to three times greater capacity than most of the DAC sorbents reported to date. The hybrid sorbent, such as other amine-based sorbents, is amenable to thermal desorption at less than 90°C. In addition, seawater was validated as a viable regenerant, and the desorbed CO2 is simultaneously sequestered as innocuous, chemically stable alkalinity (NaHCO3). The dual-mode regeneration offers unique flexibility and facilitates using oceans as decarbonizing sinks to widen DAC application opportunities.

Comparative effect of mesoporous carbon doping on the adsorption of pharmaceutical drugs in water: Theoretical calculations and mechanism study

In this study, mesoporous doped-carbons were synthesized from sucrose, a natural source, boric acid and cyanamide as precursors, generating B- or N-doped carbon. These materials were characterized by FTIR, XRD, TGA, Raman, SEM, TEM, BET, and XPS, confirming the preparation of a tridimensional doped porous structure. B-MPC and N-MPC showed a high surface specific area above 1000 m2/g. The effect of B and N doping on mesoporous carbon was evaluated on the adsorption of emerging pollutants from water. Diclofenac sodium and paracetamol were used in adsorption assays, reaching removal capacities of 78 and 101 mg.g−1, respectively. Kinetic and isothermal studies indicate the chemical nature of adsorption controlled by external and intraparticle diffusion and multilayer formation due to strong adsorbent/adsorbate interactions. DFT-based calculations and adsorption assays infer that the main attractive forces are hydrogen bonds and Lewis acid-base interactions.

Graphene Oxide-Grafted Hybrid Diblock Copolymer Brush (GO-graft-PEG6k-block-P(MA-POSS)) as Nanofillers for Enhanced Lithium Ion Conductivity of PEO-Based Nanocomposite Solid Polymer Electrolytes.

Nanocomposite solid polymer electrolytes (NSPEs) with PEO as the matrix and (i) GO or (ii) GO-graft-PEG6k or (iii) GO-graft-PEG6k-block-P(MA-POSS) as nanofillers have been fabricated to elucidate the impact of the filler morphology on the lithium ion conductivity. GO-graft-PEG6k was obtained by grafting PEG6k onto GO via esterification. GO-graft-PEG6k-block-P(MA-POSS) was prepared via surface-initiated atom transfer radical polymerization. Fourier-transform infrared spectroscopy revealed enhanced salt dissociation and complexation between the filler and PEO host that could be attributed to Lewis acid-base interactions. Electrochemical impedance spectroscopy revealed the improved ion conductivity of the fabricated NSPEs as compared with the pristine PEO-LiClO4. As an example, at 50 °C, the ion conductivity increased to 4.01 × 10-5 and 6.31 × 10-5 S cm-1 with 0.3% GO and 0.3% GO-graft-PEG6k, respectively, from 2.36 × 10-5 S cm-1 of PEO-LiClO4, suggesting that the filler with brush-like architecture (GO-graft-PEG6k) is more efficient in enhancing the ion conductivity. Further increase in filler content resulted in lowering of the ion conductivity that could be ascribed to aggregation of the filler. The most dramatic impact on conductivity was observed with the incorporation of brush-like GO-graft-PEG6k-block-P(MA-POSS) as a nanofiller (3.0 × 10-4 S cm-1 at 50 °C with 1.0 wt % filler content). The increase in ion conductivity in the current systems, as opposed to the conventional view, could not be correlated with the content of the amorphous phase of the matrix. The conduction mechanism is still unclear; nevertheless, it could be assumed that in addition to the ion conduction through the PEO matrix, the filler forms additional low-energy ion conducting channels at its interface with the matrix. The pendent POSS nanocages of GO-graft-PEG6k-block-P(MAPOSS) might probably increase the free volume at the interface with the matrix that is associated with higher chain and ion mobility, thus further enhancing the ion conductivity as compared with GO and GO-graft-PEG6k. The faster ion dynamics in 1.0 wt % GO-graft-PEG6k-block-P(MAPOSS) NSPEs has also been verified by the dielectric relaxation studies. Thus, integration of both the PEG and POSS nanocages into GO-grafted brush-like architecture offers a new tool for tuning the lithium ion conductivity for potential Li ion battery applications.

Review of Colloid (Nano‐ and Micro‐Particle) Transport and Surface Interaction in Groundwater. William P. Johnson and Eddy F. Pazmino. The Groundwater Project. 111 pp. ISBN: 978‐1‐77470‐070‐9. DOI: https://doi.org/10.21083/978‐1‐77470‐070‐9

Review of <i>Colloid (Nano‐ and Micro‐Particle) Transport and Surface Interaction in Groundwater</i>. William P. Johnson and Eddy F. Pazmino. The Groundwater Project. 111 pp. ISBN: 978‐1‐77470‐070‐9. DOI: https://doi.org/10.21083/978‐1‐77470‐070‐9

Enhancing the Chemical Stability of MXene Through Synergy of Hydrogen Bond and Coordination Bond in Aqueous Solution.

MXenes with unique physicochemical properties have shown substantial potential in electromagnetic interference (EMI) shielding. However, the chemical instability and mechanical fragility of MXenes has become a major hurdle for their application. Abundant strategies have been dedicated to improving the oxidation stability of colloidal solution or mechanical properties of films, which always come at the expense of electrical conductivity and chemical compatibility. Here, hydrogen bond (H-bond) and coordination bond are employed to achieve chemical and colloidal stability of MXenes (0.1mg mL-1 ) by occupying the reaction sites of Ti3 C2 Tx attacking of water and oxygen molecules. Compared to the Ti3 C2 Tx , the Ti3 C2 Tx modified with alanine via H-bond shows significantly improved oxidation stability (at room temperature over 35 days), while the Ti3 C2 Tx modified with cysteine by synergy of H-bond and coordination bond can be maintained even after 120 days. Simulation and experimental results verify the formation of H-bond and Ti-S bond by a Lewis acid-base interaction between Ti3 C2 Tx and cysteine. Furthermore, the synergy strategy significantly improves the mechanical strength of the assembled film (up to 78.1 ± 7.9MPa), corresponding the increment of 203% compared to untreated one, almost without compromising the electrical conductivity and EMI shielding performance.

Nitrogen-doped hydrochar prepared by biomass and nitrogen-containing wastewater for dye adsorption: Effect of nitrogen source in wastewater on the adsorption performance of hydrochar

Dye wastewater has become one of the main risk sources of environmental pollution due to its high toxicity and difficulty in degradation. Hydrochar prepared by hydrothermal carbonization (HTC) of biomass has abundant surface oxygen-containing functional groups, and therefore is used as an adsorbent to remove water pollutants. The adsorption performance of hydrochar can be enhanced after improving its surface characteristics through nitrogen-doping (N-doping). In this study, wastewater rich in nitrogen sources such as urea, melamine and ammonium chloride were selected as the water source for the preparation of HTC feedstock. The N atoms were doped in the hydrochar with a content of 3.87%–5.70%, and mainly in the form of pyridinic-N, pyrrolic-N and graphitic-N, which changed the acidity and basicity of the hydrochar surface. The N-doped hydrochar adsorbed methylene blue (MB) and congo red (CR) in wastewater through pore filling, Lewis acid-base interaction, hydrogen bond, and π-π interaction, and the maximum adsorption capacities of those were obtained with 57.52 mg/g and 62.19 mg/g, respectively. However, the adsorption performance of N-doped hydrochar was considerably affected by the acid-base property of the wastewater. In a basic environment, the surface carboxyl of the hydrochar exhibited a high negative charge and thus an enhanced electrostatic interaction with MB. Whereas, the hydrochar surface was positively charged in an acid environment by binding H+, resulting in an enhanced electrostatic interaction with CR. Therefore, the adsorption efficiency of MB and CR by N-doped hydrochar can be tuned by adjusting the nitrogen source and the pH of the wastewater.

Highly electrocatalytic active amorphous Al2O3 in porous carbon assembled on carbon cloth as an independent multifunctional interlayer for advanced lithium-sulfur batteries

To realize practical applications of lithium-sulfur batteries, rational strategies have to be applied to overcome obstacles such as the shuttle effect and sluggish reaction kinetics of soluble long-chain lithium polysulfides (LPS). In this work, highly electrocatalytic active amorphous Al2O3 uniformly dispersed in porous carbon (Al2O3/C) anchored on carbon cloth (CC) was successfully fabricated. The resultant flexible Al2O3/C@CC was used as an independent interlayer for Li-S batteries, demonstrating strong physical confinement and chemical binding ability for LPS, as well as high catalytic activity for LPS conversion kinetics due to a synergistic effect of 3D conductive network, amorphous nature of Al2O3/C, porous structure and abundant active sites. The cells with such interlayer exhibit high specific capacity, superior cycling stability and rate capability, 903 mAh/g at 0.2C after 100 cycles and 810 mAh/g at 1.0C after 300 cycles can be achieved, moreover, 741 mAh/g can still be retained at a high rate of up to 5.0C. By contrast, Al-MOF grown on carbon cloth (Al-MOF@CC) exhibits limited performance improvement due to poor electrical conductivity, low structure stability, as well as limited ion diffusion rate and weak Lewis acid-base interactions due to lack of open channels.

Critical role of extracellular DNA in the establishment and maintenance of anammox biofilms

Anaerobic ammonium oxidation (anammox) has been widely used for the sustainable removal of nitrogen from wastewater. Extracellular DNA (exDNA), as one of the main components of biofilms, not only determines the initial formation process, but also allows the three-dimensional structure to be maintained. Since the effects of exDNA on anammox biofilm formation are still poorly understood, this study elucidated the effects of exDNA on different stages of anammox biofilm establishment and maintenance under static conditions and its mechanism. The results revealed that exDNA mainly affected the maintenance stage of anammox biofilm formation. Compared with the absence of exDNA, nitrogen removal efficiency in the presence of exDNA was 6.17 % higher; the number of bacteria cells attached to the carrier was 2.23 times that in the absence of exDNA. The spatiotemporal distribution of bacteria was revealed by fluorescence in situ hybridization. After 30 days, the relative abundances of anammox in biofilms were 6.19 % and 0.4 % in the presence and absence of exDNA, respectively, indicating its positive role in anammox bacteria (AnAOB) adhesion and biofilm formation. The presence of exDNA in extracellular polymeric substances (EPS) promotes the synthesis of proteins and soluble microbial products. According to the extended Derjaguin−Landau−Verwey−Overbeek (X − DLVO) theory, the presence of exDNA also reduced the Lewis acid–base interaction energy and created favorable thermodynamic conditions for AnAOB adhesion. These findings advance our understanding of the role of exDNA in anammox-mediated biofilm formation and offer insights into the mechanism of exDNA in the establishment and maintenance stages.

Interface Manipulation of Composite Solid Polymer Electrolyte with Polydopamine to Construct Durable and Fast Li+ Conduction Pathways

Taking advantage of light weight, flexibility, and flame retardancy, solid polymer electrolytes (SPEs) provide a feasible solution to these safety concerns and to the enhancement of energy density for lithium-ion batteries (LIBs). However, the development of SPEs is still restricted by low ionic conductivity. Herein, we develop a type of SPE filler built by flower-like Co3O4 microspheres as a lithiophilic backbone and polydopamine (PDA) as a multifunctional coating for the engineering of the interphase properties of the polyether-based SPEs. The hierarchical structure of Co3O4 affords large interfacial contact area with SPEs and effectively suppresses the regular crystallinity of poly(ethylene oxide) (PEO) segments. Moreover, the PDA coating layers with diverse surface functionalities serve as a versatile mediator to finely tune ionic distribution and transport behavior via multiple Lewis acid–base interactions. We uncover the interphase characterizations and their synergistic effects to enhance Li+ conductivity and mechanical/electrochemical stability. This study provides intriguing alternatives for developing composite solid polymer electrolytes (CPEs), for which we further demonstrate the potential application of Co3O4@PDA-based CPEs in all-solid-state LIBs.

Sustainable metal-organic framework co-engineered glass fiber separators for safer and longer cycle life of Li-S batteries

Most of the issues with making Li–S batteries are caused by the growth of Li dendrites and the movement of polysulfide. To solve both of these problems at the same time, this study describes the placement of Cu or Fe atoms on an ultrathin metal organic framework (MOF) nanosheet-based glass fiber separator for making Li–S batteries that are safe and last a long time. Cu or Fe atoms coordinated with oxygen atoms on the surface of ultrathin MOF nanosheets can greatly facilitate the movement of Li ions while acting as "traps" to stop polysulfide from moving around by introducing the Lewis acid-base interaction. Because of this, the Li–S cells with the Cu/MOF or Fe/MOF coatings on the glass fiber separator show long-term cycling stabilities with low-capacity decay of 0.080% and 0.057% per cycle over 400 cycles, respectively. Furthermore, Li–S cells assembled with the Cu/MOF and Fe/MOF separators show capacity retention of 985 and 1237 mAh g−1, respectively, after 400 cycles, indicating the potential of the Cu/MOF and Fe/MOF separators for practical applications.

Self‐Healing and Recyclable Polymer Electrolyte Enabled with Boronic Ester Transesterification for Stabilizing Ion Deposition

AbstractDamage to solid polymer electrolytes can lead to mechanical degradation, short circuits, or functional failures. Therefore, introducing a self‐healing function to solid polymer electrolytes is an ideal strategy to improve the safety and reliability of electrolyte systems. Herein, dynamic boronic ester‐based self‐healing polymer electrolytes (DB‐SHPEs) with excellent mechanical properties and interfacial stability are developed via a thermally initiated ring‐opening reaction between thiol and epoxy groups. The DB‐SHPEs containing boronic ester bonds can not only alter the topologies via boronic ester transesterification and exhibit good self‐healing capability but also enable homogeneous deposition of Li ions on the Li metal through the Lewis acid–base interactions between boron atoms and salt anions. Furthermore, the boronic ester bonds can endow the DB‐SHPE with reprocessability and recyclability taking advantage of associative transesterification reaction. More significantly, the Li/DB‐SHPE/Li symmetric cells exhibit a stable voltage plateau after cycling for 1200 h and the LiFePO4/DB‐SHPE/Li batteries present excellent cycling performance, suggesting that high‐performance self‐healing polymer electrolytes with multiple functions are promising materials for the next‐generation lithium metal batteries.

Realizing Scalable Nano-SiO2-Aerogel-Reinforced Composite Polymer Electrolytes with High Ionic Conductivity via Rheology-Tuning UV Polymerization.

Polymer electrolytes for lithium metal batteries have aroused widespread interest because of their flexibility and excellent processability. However, the low ambient ionic conductivity and conventional fabrication process hinder their large-scale application. Herein, a novel polyethylene-oxide-based composite polymer electrolyte is designed and fabricated by introducing nano-SiO2 aerogel as an inorganic filler. The Lewis acid-base interaction between SiO2 and anions from Li salts facilitates the dissociation of Li+. Moreover, the SiO2 interacts with ether oxygen (EO) groups, which weakens the interaction between Li+ and EO groups. This synergistic effect produces more free Li+ in the electrolyte. Additionally, the facile rheology-tuning UV polymerization method achieves continuous coating and has potential for scalable fabrication. The composite polymer electrolyte exhibits high ambient ionic conductivity (0.68 mS cm-1) and mechanical properties (e.g., the elastic modulus of 150 MPa). Stable lithium plating/stripping for 1400 h in Li//Li symmetrical cells at 0.1 mA cm-2 is achieved. Furthermore, LiFePO4//Li full cells deliver superior discharge capacity (153 mAh g-1 at 0.5 C) and cycling stability (with a retention rate of 92.3% at 0.5 C after 250 cycles) at ambient temperature. This work provides a promising strategy for polymer-based lithium metal batteries.

Novel Al-doped UiO-66-NH2 nanoadsorbent with excellent adsorption performance for tetracycline: Adsorption behavior, mechanism, and application potential

Metal doping, an alternative strategy to enhance the adsorption performance of metal–organic frameworks (MOFs), is a hot research direction of MOF modification. However, the commonly used doping metals are mostly rare metals, which increase the cost and may lead to secondary pollution. Thus, the practical application of metal doping in MOF modification is limited. Herein, Aluminum (Al), an abundant, cheap, and environmentally friendly metal, was doped in UiO-66-NH2 to prepare Al-UiO-66-NH2 to adsorb tetracycline (TC) effectively. The optimal Al doping ratio for preparing Al-UiO-66-NH2 was determined, and the physicochemical characteristics of the prepared Al-UiO-66-NH2 were obtained. Adsorption performance and reusability were investigated. Furthermore, the possible adsorption mechanisms were explored, and the anti-interference adsorption ability and application potential were evaluated. The optimal Al doping ratio was 1:1 (Zr/Al molar ratio), and the adsorption capacity of Al-UiO-66-NH2 was 6.86 times higher than that of UiO-66-NH2. Compared with UiO-66-NH2, Al-UiO-66-NH2 had smaller particle size, larger specific surface area and pore size, and more coordinated NH2-BDC. For TC adsorption, the process was spontaneous and endothermic and fitted well with the pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity obtained by the Langmuir model was 520 mg/g. Pore filling, electronic interaction, H-bonding interaction, complexation, π-π interaction, and Lewis acid–base interaction took part in the adsorption. Al-UiO-66-NH2 could be reused, while exhibiting high water stability and a certain anti-interference performance for TC adsorption. Overall, Al-UiO-66-NH2 was an alternative MOF adsorbent for the treatment of wastewater containing TC with desirable application potential.

Crown ether as organocatalyst for reductive upgrading of CO2 to N-containing benzoheterocyclics and N-formamides

Constructions of heterocyclics by incorporation of CO2 into N-, O- and S-nucleophiles represent advance of synthetic methodology by using CO2 as a C1 feedstock. Herein, we reported crown ether (e.g. 18-crown-6)-catalyzed reductive functionalization of CO2 to various N-containing benzoheterocyclics and N-formamides in the presence of PhSiH3 under metal-free and mild conditions. Lewis acid–base interaction between PhSiH3 and 18-crown-6 enhanced hydride-donating ability of the PhSiH3, thus facilitating the CO2 insertion into the Si–H bond. A positive correlation was observed between electron-donating ability and catalytic activity of the investigated crown ethers on CO2 reduction. Crown ethers thus represent a novel organocatalytic activation model for CO2 reduction, demonstrating an important alternative for transition-metal-based catalysts.

Hydrogen Bonding Regulated Flexibility and Disorder in Hydrazone-Linked Covalent Organic Frameworks

Covalent organic framework (COF) chemistry is experiencing unprecedented development in recent decades. The current studies on COF chemistry are mainly focused on the discovery of novel covalent linkages, new topological structures, synthetic methodologies, and potential applications. However, despite the fact that noncovalent interactions are ubiquitous in COF chemistry, relatively little attention has been given to the role of noncovalent bonds on COF structures and their properties. In this work, a series of hydrazone-linked COFs involving noncovalent hydrogen bonds have been constructed, where the hydrogen-bonding interaction plays critical roles in the COF crystallinity and structures. The regulation of structural flexibility, the reversible transition between order and disorder, and the variety of host-guest interactions have been demonstrated in succession for the first time in COFs. The results obtained by the hydrogen-bonding-regulated strategy may also be extendable to other noncovalent interactions, such as π-π interactions, metal coordination interactions, Lewis acid-base interactions, etc. These findings will inspire future developments in the design, synthesis, structural regulation, and applications of COFs by manipulating noncovalent interactions.

Designing and Exploring “Visible” B←N Bond Coordination Compounds Based on Lewis Acid-Base Interaction in Laboratory Teaching

Designing and Exploring “Visible” B←N Bond Coordination Compounds Based on Lewis Acid-Base Interaction in Laboratory Teaching

Enhancing the selective electrochemical conversion of nitrate via π back-donation on Lewis acid sites induced by noble-metal doped CoP

Nitrate is a typical Lewis base, while noble-metals have unoccupied d-orbitals that can form Lewis acidic sites. Therefore, Pd/CoP can utilize Lewis acid–base interactions to promote the adsorption and conversion of NO3−.

Host-Guest Chemistry in Boron Nitride Nanotubes: Interactions with Polyoxometalates and Mechanism of Encapsulation.

Boron nitride nanotubes (BNNTs) are an emerging class of molecular container offering new functionalities and possibilities for studying molecules at the nanoscale. Herein, BNNTs are demonstrated as highly effective nanocontainers for polyoxometalate (POM) molecules. The encapsulation of POMs within BNNTs occurs spontaneously at room temperature from an aqueous solution, leading to the self-assembly of a POM@BNNT host-guest system. Analysis of the interactions between the host-nanotube and guest-molecule indicate that Lewis acid-base interactions between W═O groups of the POM (base) and B-atoms of the BNNT lattice (acid) likely play a major role in driving POM encapsulation, with photoactivated electron transfer from BNNTs to POMs in solution also contributing to the process. The transparent nature of the BNNT nanocontainer allows extensive investigation of the guest-molecules by photoluminescence, Raman, UV-vis absorption, and EPR spectroscopies. These studies revealed considerable energy and electron transfer processes between BNNTs and POMs, likely mediated via defect energy states of the BNNTs and resulting in the quenching of BNNT photoluminescence at room temperature, the emergence of new photoluminescence emissions at cryogenic temperatures (<100 K), a photochromic response, and paramagnetic signals from guest-POMs. These phenomena offer a fresh perspective on host-guest interactions at the nanoscale and open pathways for harvesting the functional properties of these hybrid systems.

Mechanochemical modified nitrogen-rich biochar derived from shrimp shell: Dominant mechanism in pyridinic-N for aquatic methylene blue removal

N-doping for the preparation of functional carbon materials is a trending research topic. In this study, N-rich biochar (BC) was prepared by calcining naturally N rich shrimp shells under oxygen-limiting environment, and the calcining temperatures were controlled. BC were activated with 5% hydrochloric acid solutions and then post-modified with ball-milling to obtain a series of novel adsorbents (MBCs). All samples were characterized by SEM, BET, FT-IR, XRD, XPS, TG, and element analysis. Surface area, pore volume, and other surface functional groups were significantly improved after acidizing and ball-milling. The adsorption capacities for MB were MBC350 > MBC500 > MBC650 >BC350 > BC650 > BC500, and the equilibrium adsorption capacities were 575.01 mg/g, 506.52 mg/g, 424.59 mg/g, 113.31 mg/g, 93.53 mg/g and 86.25 mg/g, respectively. The excellent adsorption performance of MBCs for MB was ascribed to Lewis acid-base interaction, π-π interaction, electrostatic interaction and van der Waals, and the quinone group and pyridinic-N on the surface of the MBCs are identified as the major active sites. Taken together, ball-milled shrimp shell biochar is a promising material for cation dye adsorption.