Preferred Adsorption Sites Research Articles

First-Principle Calculations on O-Doped Hexagonal Boron Nitride (H-BN) for Carbon Dioxide (CO2) Reduction into C1 Products

With the rapid growth of the world population and economy, the greenhouse effect caused by CO2 emissions is becoming more and more serious. To achieve the “two-carbon” goal as soon as possible, the carbon dioxide reduction reaction is one of the most promising strategies due to its economic and environmental friendliness. As an analog of graphene, monolayer h-BN is considered to be a potential catalyst. To systematically and theoretically study the effect of O doping on the CO2 reduction catalytic properties of monolayer h-BN, we have perform a series of first-principle calculations in this paper. The structural analysis demonstrates that O preferentially replaces N, leading to decreasing VBM of monolayer h-BN, which is conducive to improving its capability for CO2 reduction. The preferential CO2 adsorption sites on monolayer h-BN before and after O doping are the N-t site and B-t site, respectively. O doping increases the adsorption strength of CO2, which is favorable in the further hydrogenation of CO2. During the conversion of CO2 into CO and HCOOH via a two-electron pathway and CH3OH and CH4 via a six-electron pathway, O doping can reduce the energy barrier of the rate determining step (RDS) and change the key steps from uphill reactions to downhill reactions, thus increasing the probability of CO2 reduction. In conclusion, O(N)-doped h-BN exhibits the excellent CO2 reduction performance and has the potential to be a promising catalyst.

Coverage-dependent adsorption of nitric oxide (NO) on Cu(100) surface: A DFT investigation with van der Walls force

The adsorption behavior of nitric oxide (NO) on the Cu(100) surface at varying coverage levels is investigated using density functional theory (DFT) with van der Waals corrections. We examine various NO coverages on Cu(100): 0.08 ML, 0.25 ML, 0.5 ML, 0.75 ML, and 1 ML, and observe a notable transition in adsorption site preference, shifting from hollow sites at low coverage to bridge sites at higher coverage. The projected density of states (PDOS) analysis highlights changes in the electronic structure of Cu atoms. The calculated d-band center of the Cu surface shifts as the NO coverage increases, directly correlating with changes in adsorption energy. These findings provide insights into the complex interplay between adsorbate–adsorbate repulsion and surface interaction, offering a more comprehensive understanding of NO adsorption on Cu surfaces.

Insights on formation of oxide layers, corrosion, and hydrogen embrittlement on the Ti2AlNb (1 1 0) surface: Density functional theory study

Ti2AlNb alloys offer good mechanical qualities and promise for use in various applications, such as aero-engines and other industries. However, corrosion and hydrogen embrittlement remain important concerns and limitations for their use. In this work, first-principle density functional theory is used to investigate the adsorption of hydrogen, fluorine and oxygen on the surface of Ti2AlNb (110). The effects of the considered adsorbates on the surface were compared by analysing the adsorption energy, charge density differences, density of states, and work function. The current findings revealed that the adsorption behaviour of all the adsorbates is exothermic and spontaneous due to the negative adsorption energy. More importantly, the effect of Van der Waals forces and dispersion correction was considered, it was found that for all adsorbates the dispersion correction approach exhibited the most stable adsorption energies (EadsDFT-D) than the standard density functional theory (EadsDFT). Thus, the standard DFT underestimates the adsorption energy. Furthermore, it was shown that the adsorption energy strength is dependent on the surface adsorption site, with the Ti-Nb and Al-Nb bridge sites being the most preferred sites for hydrogen, fluorine and oxygen adsorption. Subsequently, it was discovered that oxygen adsorption on the surface of Ti2AlNb (110) was more thermodynamically stable than hydrogen and fluorine. This suggests that the Ti2AlNb surface will likely suffer from oxidation rather than corrosion and hydrogen embrittlement. In addition, surface atoms showed electron-charge depletion, while adsorbates showed charge accumulation. The adsorption caused charge density redistribution and altered the surface work function.

Metal-free N, P-Codoped Carbon for Syngas Production with Tunable Composition via CO2 Electrolysis: Addressing the Competition Between CO2 Reduction and H2 Evolution.

Electroreduction of carbon dioxide into value-added fine chemicals is a promising technique to realize the carbon cycle. Recently, metal-free heteroatom doped carbons are proposed as promising cost-effective electrocatalysts for CO2 reduction reaction (CO2RR). However, the lack of understanding of the active site prevents the realization of a high-performance electrocatalyst for the CO2RR. Herein, we synthesized metal-free N, P co-doped carbons (NPCs) for producing syngas, which is composed of H2 and CO, by CO2 electrolysis using inexpensive bio-based raw materials via simple pyrolysis. The syngas ratio (H2/CO) can be controlled within the high demand range (0.3-4) at low potentials using NPCs by tuning the N and P contents. In comparison with only N doping or P doping, N and P co-doping has a positive impact on improving CO2RR activity. Experimental analysis and density functional theoretical (DFT) calculations revealed that negatively charged C atoms adjacent to N and P atoms are the most favorable active sites for CO2-to-CO conversion compared to pyridinic N on N, P co-doped carbon. Introducing N atoms generates the preferable CO2 adsorption site, and P atoms contribute to decreasing the Gibbs free energy barrier for key *COOH intermediates adsorbed on the negatively charged C atoms.

Low-Energy Magnetic States of Tb Adatom on Graphene.

Electronic structure and magnetic interactions of a Tb adatom on graphene are investigated from first principles using combination of density functional theory and multiconfigurational quantum chemistry techniques including spin-orbit coupling. We determine that the six-fold symmetry hollow site is the preferred adsorption site and we investigate electronic spectrum for different adatom oxidation states including Tb3+, Tb2+,Tb1+, and Tb0. For all charge states, the Tb 4f8configuration is retained with other adatom valence electrons being distributed over 5dxy, 5dx2+y2, and 6s/5d0single-electron orbitals. We find strong intra-site adatom exchange coupling that ensures that the 5d6sspins are parallel to the 4fspin. For Tb3+, the energy levels can be described by theJ= 6 multiplet split by the graphene crystal field. For other oxidation states, the interaction of 4felectrons with spin and orbital degrees of freedom of 6s5delectrons in the presence of spin-orbit coupling results in the low-energy spectrum composed closely lying effective multiplets that are split by the graphene crystal field. Stable magnetic moment is predicted for Tb3+and Tb2+adatoms due to uniaxial magnetic anisotropy and effective anisotropy barrier around 440 cm-1controlled by the temperature assisted quantum tunneling of magnetization through the third excited doublet. On the other hand, in-plane magnetic anisotropy is found for Tb1+and Tb0adatoms. Our results indicate that the occupation of the 6s5dorbitals can dramatically affect the magnetic anisotropy and magnetic moment stability of rare earth adatoms.

A distinct role of microstructure on hot corrosion behaviour of additively manufactured IN718

The influence of LPBF-IN718 microstructure on hot corrosion behavior was studied at 650 °C. The H-IN718 with <001> oriented grains undergo more weight changes than V-IN718 with <110> oriented grains. Detailed characterization analysis corroborates that Rapp-Goto fluxing and sulphidation mechanisms are operating in LPBF-IN718 with 3SM. Further, GDOES confirms the sulphur gradient existence between Air/3SM and 3SM/H-IN718 interfaces. It suggests that <001> oriented grains serve as preferred sites for ion adsorption and reactions, which might facilitate the sulfur diffusion more effectively than other grain orientations. As a result, oxy-anions generated during sulfidation enhance the fluxing mechanism, thus increasing weight gain in H-IN718.

DFT calculations with and without spin polarization of the adsorption and decomposition of NCO and OCN on the Ag(110) surface

The adsorption of C, N, O, CO, CN, NCO and OCN, as well as the decomposition of NCO and OCN on the Ag(110) surface were studied using the density functional theory (DFT) with and without spin polarization combined with the periodic slab model, at a 0.25 ML coverage. Adsorption energy, preferred adsorption site, structural parameters, diffusion barrier of each species were determined. Work function and dipole moment changes of the Ag(110) surface allowed us to determine the direction of the charge transfer. We analyzed the interaction between the adsorbate and the surface, in the framework of the Local density of states (LDOS). Our results have revealed that the C, N and O atoms were stable on the top and hollow sites. The CN, NCO and OCN molecules bind strongly with the Ag(110) surface. While, the CO molecule weakly adsorbs on the Ag(110) surface. We found that the NCO and OCN thermochemical decomposition on the Ag(110) surface is not favorable. The CI-NEB calculations have also confirmed that the NCO and OCN decomposition on the Ag(110) surface was endothermic.

Stable Zinc Metal Battery Development: Using Fibrous Zirconia for Rapid Surface Conduction of Zinc Ions With Modified Water Solvation Structure.

The two most critical technical issues in Zn-based batteries, dendrite formation, and hydrogen evolution reaction, can be simultaneously addressed by introducing negatively charged fibrous ZrO2 as a separator. Electron redistribution between ZrO2 and Zn2+ ions renders the ZrO2 surface a preferred adsorption site for Zn2+ ions, making surface conduction the primary ion-transport mode. Surface conduction enables fibrous ZrO2 to exhibit a 6.54 times higher single-Zn-ion conductivity than that of conventional glass fiber, minimizing the concentration gradient of Zn2+ and suppressing dendrite formation. Additionally, strong Zr─O─Zn bonding stabilizes the Zn2+ ions with fewer solvated H2O molecules (≈2), preventing water molecules from approaching the electrode surface, as evidenced by a 58.8% decrease in the hydrogen evolution rate. Consequently, the cycling stability of a fibrous-ZrO2-based Zn/Zn symmetric cell (3000h at 1mAhcm-2 and 5mAcm-2) is approximately ten times greater than that of the conventional variant. Furthermore, a fibrous-ZrO2-based Zn-I2 full cell exhibits a notably high energy density (271.4Whkg-1) as well as a long lifespan (≈5000 cycles) at an ultrahigh current density (4Ag-1).

Experimental and DFT studies of mercury adsorption and oxidation on CuCo2O4(110) surface

Elemental mercury (Hg0) is a typical toxic pollutant in flue gas from coal-fired power plants. The specific role of oxygen transfer on Hg0 oxidation over CuCo2O4 oxygen carrier and the involved reaction mechanisms were systematically studied by experimental and theoretical methods. In this study, the CuCo2O4 oxygen carrier with spinel-structure was prepared with salt-assisted combustion method. To reduce the grain size and increase the specific surface area of the oxygen carrier, the optimal KCl: CuCo2O4 ratio of 1:1 was obtained. Oxygen uncoupling ability of CuCo2O4 oxygen carrier was very strong, and the oxygen-releasing performance was slightly decreased after ten cyclic processes. Simulation based on density functional theory (DFT) shows that CuCo2O4 has relative low oxygen vacancy formation energy and oxygen transport energy barrier, and the oxygen vacancy is the preferred O2 adsorption site. Hg0 removal experiments show that CuCo2O4 has a strong ability to remove Hg0. The proportion of Hg2+ increases with the temperature, and the proportion of HgP decreases accordingly. Simulation shows that the 3-Co site on the surface of the CuCo2O4 oxygen carrier is the optimum Hg0 adsorption site. CuCo2O4 is found as a strong oxygen-releasing oxygen carrier, which can effectively promote the oxidation of Hg0.

Understanding the Adsorption Kinetics of Acetone in Humid Activated Carbons: Perspectives from Adsorption-Breakthrough Experiments and Molecular Simulations.

The presence of water vapor influences the adsorption equilibrium and kinetics of volatile organic compounds (VOCs) in porous materials. By combination of breakthrough experiments and molecular simulations, the competitive adsorption mechanisms of water vapor and acetone on activated carbon with different textures and surface chemical properties at different humidity levels were investigated. Adsorption capacity decreases with increasing relative humidity owing to the formation of preferential adsorption sites between water and the activated carbon surface, while the adsorption rate initially increases and then decreases with increasing relative humidity. Experimental and simulation results revealed that the existence of a small amount of water changed the pore size distributions of activated carbon, thereby promoting the diffusion of acetone molecules. As the relative humidity increased, a portion of the acetone dissolved in water, resulting in a reduction in the adsorption rate. The response of different functional groups to relative humidity was further clarified by molecular simulation. Activated carbons with a high electrostatic interaction with acetone were less affected by humidity and thus exhibit greater potential as adsorbents.

Comparative study of CO adsorption on Au, Cu, MoO2 and MoS2 2D Nanoparticles

This study focuses on a comparative analysis of the electronic properties of triangular, irregular hexagonal, and octagonal 2D nanoparticles containing 10, 12, and 14 motifs, made of Au, Cu, MoO2, and MoS2. The investigation was carried out using density functional theory. The formation energies and vibrational frequencies demonstrate that the 2D nanostructure configurations can exist as stable structures. Edge atoms with lower coordination numbers than central atoms, are the preferred sites for CO adsorption. Using orbital-weighting dual descriptors calculated from Fukui functions enabled the identification of a majority nucleophilic attack sites in Au and Cu nanoparticles, while MoO2 and MoS2-based nanoparticles present almost as many electrophilic sites as nucleophilic sites. The charge transferred between the nanostructures and the CO molecule and the redistribution of the projected density of states were used to assess the strength of interfacial bonds and the nature of the fundamental interaction involved in the bonding.

Crystal Step‐Induced Uniform and Rapid Deposition on Zinc Anodes

AbstractAqueous Zn‐ion batteries have emerged as promising candidates for large‐scale energy storage owing to their high safety and low cost. However, dendrite growth and side reactions compromise the stability of the Zn anode in practical applications. Here, a novel Zn anode featuring well‐designed crystal steps along the (002) facets, referred to as Step‐Zn is introduced. The intersections of the (002) and (100) planes in these crystal steps create preferential adsorption sites for Zn2⁺ ions, promoting initial electro‐epitaxial growth of Zn that uniformly covers the crystal steps. This process effectively regulates subsequent Zn deposition, ensuring fast reaction kinetics and smooth morphology without dendrite formation. Consequently, the unique Step‐Zn anode exhibits excellent cycle life over 6000 times at 3 mA cm−2 and low greatly reduced polarization voltage under high areal currents and capacities. Integrated with activated carbon (AC) cathode, the Step‐Zn||AC full cell demonstrates excellent durability over 10 000 cycles at 5 A g−1. This work offers valuable insights into controlling Zn deposition modes by engineering the surface microstructure of Zn anodes with greatly extended cycling stability.

Unveiling Inequality of Atoms in Ultrasmall Pt Clusters: Oxygen Adsorption Limited to the Uppermost Atomic Layer

The concept of preferential atomic and molecular adsorption site is of primary relevance in heterogeneous catalysis. In the case of ultrasmall size‐selected clusters, distinguishing the role played by each atom in a reaction is extremely challenging due to their reduced size and peculiar structures. Herein, it is revealed how the inequivalent atoms composing graphene‐supported Pt12 and Pt13 clusters behave differently in the photoinduced dissociation of O2, with only those in the uppermost layer of the clusters being involved in the reaction. In this process, the epitaxial graphene support plays a fundamental active role: its corrugation and pinning induced by the presence of the clusters are crucial for defining the preferential adsorption site on the Pt atomic agglomerates, facilitating the lateral diffusion of physisorbed oxygen at a distance that induces its selective adsorption in the topmost layer of the clusters, and inducing an inhomogeneous charge distribution within the clusters which directly affects the O2 adsorption. The inhomogeneous oxidation of the clusters is resolved by means of synchrotron‐based X‐ray photoelectron spectroscopy and supported by ab initio density functional theory calculations. The possibility to identify the active sites on Pt clusters induced by cluster–support interactions has the potential to enhance the experimentally supported design of nanocatalysts.

Magnetic interactions in chromium adsorption on silicene

Silicon is a material with well established technological applications. Thus, obtaining this material in nanostructured form increases its possibility of integration in the current technology. Silicene, a two-dimensional allotrope of silicon, has a natural compatibility with current silicon-based technology. In this work we use density-functional theory to identify the electronic and magnetic properties of chromium atoms on monolayer and bilayer silicene. We investigate several properties of chromium in silicene, such as dopant solubility limits, site preference for adsorption and charge transfer. We find that magnetization depends on key parameters such as buckling, interlayer distance and adsorption site. Chromium intercalated in silicene bilayers showed a very interesting relation between the buckling of silicene and the total magnetic moment. The larger is the buckling the smaller is the magnetic moment. Our results demonstrate that it is possible to manipulate the magnetic properties of silicene by changing chromium concentration, adsorption site and structural parameters of the host material.

Treatability of odorous dioxanes/dioxolanes in source water: How does molecular flexibility and pre-oxidation affect odorant adsorption

Odorous dioxanes and dioxolanes, a class of cyclic acetals often produced as byproducts in polyester resin manufacturing, are problematic in drinking water treatment due to their low odor thresholds and resistance to conventional treatment technology. Our research focuses on the removal of ten dioxane/dioxolane compounds through oxidation and adsorption processes, exploring the key molecular properties that govern the treatmentability. We discovered that both chlorination and permanganate oxidation were largely ineffective at degrading cyclic acetals, achieving less than 20% removal even at high applicable doses. Conversely, powdered activated carbon (PAC) adsorption proved to be a more effective method, with a removal of > 90% at a PAC dosage of 10 mg/L for seven out of ten compounds. The presence of natural organic matter (NOM) reduced PAC adsorbability for all odorants, but the deterioration level substantially varied and mostly affected by structural flexibility as indicated by the number of rotatable bonds. The results of both the experimental investigation and molecular simulation corroborated the hypothesis that more rotatable bonds (from one to three here) are indicative of greater structural flexibility, which in consequence determines the susceptibility of cyclic acetals to NOM competitive adsorption. Increased structural flexibility could facilitate greater entry into silt-like micropores or achieve preferential adsorption sites with more compatible morphology against NOM competition. When pre-oxidation (chlorination and permanganate oxidation) and adsorption were applied sequentially, additional low molecular weight NOM components produced by pre-oxidation resulted in intensified NOM competition and decreased odorant adsorbability. If this combination is inevitably required for algae and odorant control, it would be beneficial to utilize a wise screen for oxidants and a reduced oxidant dose (less than 2 mg/L) to mitigate the deterioration of odorant adsorption. This study elucidates the roles of structural flexibility in influencing the treatability of dioxanes and dioxolanes, extending beyond the solely well-established effects of hydrophobicity. It also presents rational practice guidelines for the combination of pre-oxidation and adsorption in addressing odor incidents associated with dioxane and dioxolane compounds.

Molecular dissociation of nitric oxide (NO) on VO2(010) surface : A DFT study including vdW forces

The adsorption and coadsorption of O and N atomic species, as well as the dissociation of NO molecule on VO2(010) surface have been studied using the density functional theory (DFT) with GGA-PBE as the exchange–correlation, including van der Waals (vdW) corrections of the form PBE+vdW-DF2. We found that the short-bridge (sb) site is the energetically most stable for both N and O atoms. The inclusion of PBE+vdW-DF2 corrections does not change the preferred adsorption site, however it reduces the value of the adsorption energy relative to ordinary GGA-PBE functional. Also, while the GGA-PBE functional results in finite magnetization on the O and N atoms when adsorbed on the VO2 surface, the inclusion of the vdW forces results in zero magnetization of the atoms. In addition, our Löwdin charge transfer analysis shows electron transfer from the VO2(010) surface to the O atom, which is further supported by an accumulation of charge density around the O atom as well as the charge depletion from the V surface atoms. At a lower coverage θ= 0.25 ML, the N atom behaves like a charge acceptor, that is, electrons are transferred from the VO2 surface to it. At a higher coverage θ= 0.50 ML and 0.75 ML, the N atom behaves like a charge donor, i.e., there is a transfer of electronic charges to the VO2 surface. We emphasize that charge transfer between the adsorbate (O and N) and the surface establishes adsorbate-surface bonding which enhances the stability of the adsorbate. Furthermore, our nudged elastic band calculations (NEB) for determining the minimum energy path (MEP) and activation barrier energy (Ea) for NO dissociation into N and O atoms show Ea= 2.18 eV (1.78 eV) as obtained using the GGA-PBE (PBE+vdW-DF2) functionals. Regarding potential application, this study thus contributes to reducing the amount and harmful effect of NO gas in the atmosphere.

The electronic, magnetic, and optical behaviors of graphyne modulated by metal atoms adsorption: a first-principles study

The electronic, magnetic, and optical behaviors of graphyne modulated by various adsorbed metal atoms (Li, Na, K, Mg, Ca, Al, and Zn) from typical metal-ion batteries are studied by first-principles calculation. Notably, Mg and Zn adsorption systems are deemed unstable. In contrast, Li, Na, K, Ca, and Al systems exhibit two preferential adsorption sites, with the optimal position being the hollow center site within the large acetylenic ring. Upon the adsorption of these metal atoms, except for Ca adsorption systems exhibit semi-metallic behavior, while the other metal adsorption systems induced a transition from p-type to n-type semiconductors with decreased band gaps. Intriguingly, the inherent magnetism of the metal atoms vanished, resulting in a total magnetic moment of 0 μ B for the adsorption systems. Furthermore, the optical absorption and reflectivity peak positions for Ca adsorption systems show a significant redshift from violet to green and blue light regions. Conversely, other adsorption systems exhibit new absorption and reflection peaks in the infrared range, accompanied by an increase in both absorption coefficient and reflectivity across various spectral regions. These findings are conducive to the application in the field of novel optoelectronics and optical films.

Thermal effects of organic porous media on absorption and desorption behaviors of carbon dioxide

As a result of global warming, people are increasingly concerned about greenhouse gas emissions, particularly carbon dioxide (CO2). Many countries have been promoting carbon capture, storage (CCS) projects in order to alleviate climate degradation and achieve net zero carbon emissions. To study the thermal effects of organic porous media on CO2 absorption and desorption, molecular dynamics coupled with Monte Carlo (MDMC) were used in this study. A part of the CO2 molecules will be trapped within kerogen matrix due to its complex porous structure. The affinity of kerogen to CO2 facilitates CO2′s adsorption within the kerogen porous media, resulting in a heterogeneous distribution of CO2. The kerogen forms high potential energy peaks and low potential energy wells in the matrix, which provide preferred adsorption sites for CO2 in the porous space. The low stress state of CO2 also indicates that it prefers adsorption in the matrix as CO2 performs a lower potential energy state in the kerogen matrix than in the bulk phase. This study examines different thermal effects of kerogen, and results indicate that increasing CO2 thermal motion facilitates its absorption, while a high temperature matrix promotes CO2 desorption. Adsorbed layer provides resistance for CO2′s diffusion behaviors. The free energy of CO2′s diffusion is analyzed in relation to its mechanism, revealing that irregular thermal motion causes uncertainty in the adsorption capacity.

Preferential adsorption of medium molecular weight proteins in extracellular polymeric substance alleviates toxicity of small-sized microplastics to Skeletonema costatum

Extracellular polymeric substances (EPS) secreted by organisms tend to encapsulate microplastics (MPs), forming an EPS-corona that affects the fate of MPs in marine ecosystems. However, the impact of the EPS-corona on the biotoxicity of MPs to marine organisms remains poorly understood. Herein, the effect of the EPS-corona on the toxicity of polystyrene (PS) MPs of different sizes (0.1 and 1 µm) to Skeletonema costatum (S. costatum) was investigated. The preferential adsorption of medium molecule weight (∼55 kDa) proteins onto PS MPs mainly contributed to the EPS-corona formation, decreasing the surface charge negativity of small-sized PS MPs (0.1 µm) by 72.4 %. Nitrogen (N) and oxygen (O) moieties in polysaccharides and proteins were identified as the preferential adsorption sites in the EPS-PS MPs interaction. Density functional theory (DFT) calculations confirmed the nuclear magnetic resonance spectroscopy (NMR) results, revealing that the binding mode between EPS and PS MPs was mainly hydrogen bonding. In addition, EPS-corona increased the cell density of S. costatum by 35.5–36.0 % when exposed to small-sized PS MPs (0.1 µm, 25–50 mg/L). These findings provide new insights into how EPS-corona affects the environmental fate and ecological risks associated with micro- and nano-sized plastics in marine ecosystems.

Simple and modified chitosan gel beads from a natural source as a bio-sorbent for water defluoridation: Experimental and computational perspectives

Water contaminated with fluoride (F -) is widely acknowledged as a major global issue that poses serious health and environmental risks. Adsorption is one of the many fluoride removal treatment methods that has been widely and successfully investigated. In this work, we describe a simple process for making both cross-linked and uncross-linked chitosan gel beads from shrimp waste. SEM, FTIR, XRD and TGA analysis confirmed the successful synthesis of the non-cross-linked chitosan gel beads (Cs beads) and cross-linked chitosan gel (Cs-Ech beads) whose swelling behavior, stability and fluoride removal efficiency were studied. The adsorption conditions were also optimised. An adsorption capacity of 16.59 mg/g was achieved after just 30 min and at pH = 6.8, 10 mg/L and T = 25 °C. It was shown that chitosan gel beads cross-linked with epichlorohydrin removed more fluoride than non-cross-linked chitosan gel beads. The rate of adsorption of fluoride ions is determined by the pseudo-first order kinetic equation. On the other hand, equilibrium data was best described by Langmuir adsorption isotherms. Density functional theory calculations (DFT) based on quantitative analyses were used to explore the interfacial interaction mechanisms, offering valuable perspectives on the inter- and intra-molecular interactions. Further studies on weak interaction were conducted, focusing on the binding contribution of electrostatic interaction and vdW potential. DFT results confirmed the strong adsorption capacity and coordination behavior of F - ions on the cross-linked Cs-Ech, suggesting that the Ech group offers preferred adsorption sites.