Hard Soft Acid Base Research Articles

Rational Pathways to Ordered Multianion Chalcogenides Using Retrosynthetic Crystal Chemistry.

Mixed-anion chalcogenides make up a versatile class of materials with properties that can be fine-tuned for specific applications. While chalcogen anions (Q = S, Se, or Te) tend to form solid solutions in simple binary systems, ordering does occur in structures that have more than one unique anion site. Here, we use crystallographic analysis and hard-soft acid-base principles to predict the Wyckoff positions that secondary chalcogens will occupy in a range of single-anion hosts. The analysis serves as a guide for generating ordered sulfoselenide, selenotelluride, and sulfotelluride products in a predictable manner. The study focuses on ternary and quaternary systems with varying compositional and structural features, with an emphasis on 3D CsCu5Q3 (P42/mnm) and 2D NaCuZrQ3 (Pnma) crystal systems. The samples were prepared by using high-temperature solid-state methods and structurally characterized by using single-crystal X-ray diffraction. Ordering in the mixed-anion products is attributed to the size and bonding variance across the chalcogen series. The degree of ordering varies according to the distinctiveness of the local chemistry at the anion sites and additionally the specific combination of chalcogens employed in the reaction. Additionally, we find that mixed-chalcogen products can adopt phases that are distinct from their single-anion end members, including KCuZrTe2S (P21/m), where an alternate arrangement of polyhedral building blocks maximizes favorable bonding interactions. Density-functional theory calculations corroborate the experimental findings and offer additional insights into the ordering trends. We anticipate that the reverse-engineering approach, which is inspired by the retrosynthetic analyses used in molecular chemistry, will help accelerate the discovery and understanding of heteroanionic phenomena.

Delocalization State-Stabilized Znδ+ Active Sites for Highly Selective and Durable CO2 Electroreduction.

Zinc (Zn)-based materials are cost-effective and promising single-metal catalysts for CO2 electroreduction to CO but is still challenged by low selectivity and long-term stability. Undercoordinated Zn (Znδ+) sites have been demonstrated to be powerful active centers with appropriate *COOH affinity for efficient CO production However, electrochemical reduction conditions generally cause the inevitable reduction of Znδ+, resulting in the decline of CO efficiency over prolonged operation. Herein, a Zn cyanamide (ZnNCN) catalyst is constructed for highly selective and durable CO2 electroreduction, wherein the delocalized Zn d-electrons and resonant structure of cyanamide ligand prevent the self-reduction of ZnNCN and maintain Znδ+ sites under cathodic conditions. The mechanism studies based on density functional theory and operando spectroscopies indicate that delocalized Znδ+ site can stabilize the key *COOH intermediate through hard-soft acid-base theory, therefore thermodynamically promoting CO2-to-CO conversion. Consequently, ZnNCN delivers a CO Faradaic efficiency (FE) of up to 93.9% and further exhibits a remarkable stability lifespan of 96h, representing a significant advancement in developing robust Zn-based electrocatalysts. Beyond expanding the variety of CO2 reduction catalysts, this work also offers insights into understanding the structure-function sensitivity and controlling dynamic active sites.

Facile preparation of NiFe2O4 decorated chitosan-graphene oxide for efficient remediation of Co(II) and adsorption mechanism

In the background of severe water pollution, adsorption is a charming technique for heavy metal remediation. In this work, NiFe2O4 decorated chitosan-graphene oxide (NFCG) was prepared by simple hydrothermal method for Co(II) remediation application. Adsorption mechanism was elaborately elucidated based on multiple evidences extracted from adsorption fitting (isotherms, thermodynamics and kinetics), spectroscopic test (XPS, UV–Vis absorption, fluorescent emission and Raman spectra) and the hard-soft acid-base (HSAB) theory inspection. Result shows, for Co(II) with initial concentration 200 mg·L−1, NFCG with dosage 500 mg·L−1 reaches adsorption equilibrium in 24 min, rendering removal percentage and adsorption amount 96.87 % and 387.48 mg·g−1, respectively. Owing to the efficient recovery enabled by paramagnetism, NFCG keeps adsorption amount 311.01 mg·g−1 for Co(II) after six consecutive cycles. Moreover, NFCG exhibits selectivity towards Co(II) under the coexistence of common interfering substances. Adsorption fitting suggests chemical adsorption based on heterogeneous affinity. Spectroscopic analysis discloses, CO, CO, -C(=O)NH-, OH and aromatic part contribute to Co(II) adsorption via electron donation, forming CoO bond. This atomic scale adsorption mechanism was substantiated by HSAB theory calculation. In brief, this work provides basic knowledge and technical support for fabricating high efficiency magnetic bio adsorbent.

AI-assisted models to predict chemotherapy drugs modified with C60 fullerene derivatives.

Employing quantitative structure-activity relationship (QSAR)/ quantitative structure-property relationship (QSPR) models, this study explores the application of fullerene derivatives as nanocarriers for breast cancer chemotherapy drugs. Isolated drugs and two drug-fullerene complexes (i.e., drug-pristine C60 fullerene and drug-carboxyfullerene C60-COOH) were investigated with the protein CXCR7 as the molecular docking target. The research involved over 30 drugs and employed Pearson's hard-soft acid-base theory and common QSAR/QSPR descriptors to build predictive models for the docking scores. Energetic descriptors were computed using quantum chemistry at the density functional-based tight binding DFTB3 level. The results indicate that drug-fullerene complexes interact more with CXCR7 than isolated drugs. Specific binding sites were identified, with varying locations for each drug complex. Predictive models, developed using multiple linear regression and IBM Watson artificial intelligence (AI), achieved mean absolute percentage errors below 12%, driven by AI-identified key variables. The predictive models included mainly quantitative descriptors collected from datasets as well as computed ones. In addition, a water-soluble fullerene was used to compare results obtained by DFTB3 with a conventional density functional theory approach. These findings promise to enhance breast cancer chemotherapy by leveraging fullerene-based drug nanocarriers.

High Performance and Selective Sequestration of Cd(II) from Water by Layered Thiophosphate.

The extensive use of toxic cadmium (Cd) in energy conversion and industrial applications ranging from solar cells and battery appliances to paints and pigments contaminates water bodies. However, the upper limit of Cd contamination in drinking water is to be only 3 ppb by the WHO and 5 ppb by the USA-EPA, which underscores the need for cost-effective, efficient, and ppb level capture of Cd from contaminated water. Leveraging the selectivity due to Lewis's hard-soft acid-base (HSAB) theory, we have achieved swift and highly selective capture of Cd(II) ions from aqueous mediums using layered potassium manganese thiophosphate (K-MnPS3). K-MnPS3 effectively removes Cd(II) ions from extremely dilute aqueous solutions (ppb levels), achieving a maximum sorption capacity of 405.43 mg/g and a removal rate exceeding 97% within 20 min. Even in the presence of competing ions such as Na+, Mg2+, Ca2+, and Pb2+, K-MnPS3 remains selective. Additionally, it operates efficiently across a wide pH range (1.78-11.19) with a high distribution coefficient (∼104 mL/g). Breakthrough experiments using a 1 wt % K-MnPS3 and 99 wt % sand column showed complete breakthrough of Cd(II) after 62 h, leading K-MnPS3 as a promising candidate for Cd(II) removal from industrial effluents.

Selective Recycling of Spent Lithium‐Ion Batteries Enables Toward Aqueous Zn‐Ion Batteries Cathode

AbstractEffective selective recycling of spent lithium‐ion batteries (S‐LIBs) and giving recycled products a “second life” are crucial for advancing energy supply circularity, environmental and economic sustainability development. However, separating metal compounds with similar charge differences requires substantial energy, water, and chemical inputs. Herein, an innovative strategy is present for selective recycling S‐LIBs by photoexcitation inspired by the Hard Soft Acid Base (HSAB) principle. Theoretical calculations and experimental results show that photoexcitation drives charge transfer and modulates subtle charge density differences among metal components, thereby enhancing their solubility disparity and facilitating metal separation. Remarkably, the photoexcitation‐induced metal separation factor reaches 46900 and the metal recovery efficiency approaches 100%, representing a significant improvement over non‐photoexcitation separation with a separation factor of non‐photoexcitation of merely 2.7. Through techno‐economic analysis, the viability of photoexcitation selective recycling technology has been confirmed as an eco‐friendly and economical approach for battery recycling. Furthermore, high‐value reuse of recovered Mn components is implemented. The Recycled Mn components are treated by calcination to obtain porous, defect‐rich Mn2O3, which showed a specific capacity of 613 mAh g−1 at 0.1 A g−1) in aqueous Zn‐ion batteries (AZIBs). This work provides fresh insight into recycling S‐LIBs and moving toward more sustainable storage technologies.

Water-Soluble Lead Sulfide Nanoparticles: Direct Synthesis and Ligand Exchange Routes.

Colloidal semiconductor nanoparticles (NPs) represent an emergent state of matter with unique properties, bridging bulk materials and molecular structures. Their distinct physical attributes, such as bandgap and photoluminescence, are intricately tied to their size and morphology. Ligand passivation plays a crucial role in shaping NPs and determining their physical properties. Ligand exchange (LE) offers a versatile approach to tailoring NP properties, often guided by Pearson's Hard-Soft Acid-Base theory. Lead sulfide (PbS), a semiconductor of considerable interest, exhibits size-dependent tunable bandgaps from the infrared to the visible range. Here, we present two methods for synthesizing water-soluble, polyvinylpyrrolidone (PVP)-coated PbS NPs. The first involves direct synthesis in an aqueous solution while utilizing PVP as the surfactant for the formation of nano-cubes with a crystal coherence length of ~30 nm, while the second involves LE from octadecylamine-coated PbS truncated nano-cubes to PVP-coated PbS NPs with a crystal coherence length of ~15 nm. Multiple characterization techniques, including X-ray diffraction, transmission electron microscopy, Fourier-transform infrared spectroscopy, and thermal gravimetric analysis, confirmed the results of the synthesis and allowed us to monitor the ligand exchange process. Our findings demonstrate efficient and environmentally friendly approaches for synthesizing PVP-coated PbS NPs.

Selective Adsorption of Hazardous Substances from Wastewater by Hierarchical Oxide Composites: A Review.

Large volumes of wastewater containing toxic contaminants (e.g., heavy metal ions, organic dyes, etc.) are produced from industrial processes including electroplating, mining, petroleum exploitation, metal smelting, etc., and proper treatment prior to their discharge is mandatory in order to alleviate the impacts on aquatic ecosystems. Adsorption is one of the most effective and practical methods for removing toxic substances from wastewater due to its simplicity, flexibility, and economics. Recently, hierarchical oxide composites with diverse morphologies at the micro/nanometer scale, and the combination advantages of oxides and composite components have been received wide concern in the field of adsorption due to their multi-level structures, easy functionalization characteristic resulting in their large transport passages, high surface areas, full exposure of active sites, and good stability. This review summarizes the recent progress on their typical preparation methods, mainly including the hydrothermal/solvothermal method, coprecipitation method, template method, polymerization method, etc., in the field of selective adsorption and competitive adsorption of hazardous substances from wastewater. Their formation processes and different selective adsorption mechanisms, mainly including molecular/ion imprinting technology, surface charge effect, hard-soft acid-base theory, synergistic effect, and special functionalization, were critically reviewed. The key to hierarchical oxide composites research in the future is the development of facile, repeatable, efficient, and scale preparation methods and their dynamic adsorption with excellent cyclic regeneration adsorption performance instead of static adsorption for actual wastewater. This review is beneficial to broaden a new horizon for rational design and preparation of hierarchical oxide materials with selective adsorption of hazardous substances for wastewater treatment.

Microwave-synthesized heteroaromatic porous organic polymers for CO2 capture and hydrogen storage

In this paper, three porous organic polymers (POPs) were synthesized by microwave-assisted Friedel-Crafts polymerization reaction of 1,3,5-tris(2-thienyl)benzene (TTB) with furan (HAF), thiophene (HAT), and pyrrole (HAP) in the presence of dimethoxymethane using anhydrous iron (III) chloride as a catalyst. The polymers displayed inherent porosity, with BET surface areas ranging from 528 to 634 m2/g. These polymers exhibited high CO2 adsorption capacity, with values of 2.61, 2.17, and 2.37 mmol/g at 273 K and 1 atm, as well as strong affinity, with Qst values of 43–48 kJ/mol. The polymers showed hydrogen storage of 3.3–5.3 mmol/g (0.66–1.06 wt%) at 77 K, and 1 atm. The polymers showed Initial slope selectivity for CO2/N2: 34–61 at 273 K and 1 atm, and 23–57 at 298 K and 1 atm. Whereas, the polymers showed initial slope selectivity for CO2/CH4: 5–9 at 273 K and 4–7 at 298 K and 1 atm. Besides, the HAP at 273 K and HAF at 298 K showed highest IAST selectivity values of 231.18 and 257.49, respectively. Grand Canonical Monte Carlo (GCMC) simulations revealed that the polymers exhibit matching electronic properties with CO2 molecules and achieve excellent selectivity in accordance with the hard-soft acid-base (HSAB) theory. These findings demonstrate the potential of these polymers for CO2 capture and clean energy applications.

Building a High-Potential Silver-Sulfur Redox Reaction Based on the Hard-Soft Acid-Base Theory.

Sulfur holds immense promise for battery applications owing to its abundant availability, low cost, and high capacity. Currently, sulfur is commonly combined with alkali or alkaline earth metals in metal-sulfur batteries. However, these batteries universally face challenges in cycling stability due to the inevitable issue of polysulfide dissolution and shuttling. Additionally, the inferior stability of metal sulfide discharge compounds results in low S0/S2- redox potentials (<-0.41 V vs SHE). Herein, we leverage the principle of the hard-soft acid-base theory to introduce a novel silver-sulfur (Ag-S) battery system, which operates on the reaction between the soft acid of Ag+ and the soft base of S2-. Due to their high reaction affinity, the discharge compound of silver sulfide (Ag2S) is intrinsically insoluble and fundamentally stable. This not only resolves the polysulfide dissolution issue but also leads to a predominantly high S0/S2- redox potential (+1.0 V vs. SHE). We thus exploit the Ag-S reaction for a primary zinc battery application, which exhibits a high capacity of ∼620 mAh g-1 and a high voltage of ∼1.45 V. This work offers valuable insights into the application of classic chemistry theories in the development of innovative energy storage devices.

Enhanced performance of electrospun PVDF membranes modified with rare-earth metal oxides for membrane distillation: A systematic study

In the presented studies, the novel type of separation materials dedicated to membrane distillation was generated and systematically analyzed. Utilizing poly(vinylidene fluoride) (PVDF) electrospun membranes as a base, hybrid organic-inorganic materials were developed to enhance performance. These materials exhibited high hydrophobicity, featuring superhydrophobicity on a micro-scale due to fractal-like structures on the inorganic domain surface. Rare-earth metal oxides (REMO) were implemented for the first time as smart modifiers, covalently attached to the functionalized membrane surface. Three REMO types were selected to investigate their impact on membrane performance in air-gap membrane distillation (AGMD) for the desalination process. Chemical attachment via long enough linkers formed a flexible active surface structure, facilitating transport and separation. Dynamic goniometric studies evaluated membrane wetting stability. Particularly noteworthy was the membrane enhanced with Ho2O3 particles, with high flux and salt rejection rates of 14.41 ± 1.35 kg m−2 h−1 and >99.5 %, respectively. The membrane stability and affinity were further examined using Hansen Solubility Parameters and Pearson's hard–soft acid–base (HSAB) theory. The potential of the hybrid membranes is seen not only in desalination. With the ability to control surface properties by using different silane linkers, oleophobicity/oleophilicity can be achieved, and practical use in wastewater treatment or oil/water separation is possible.

Tailored coordination chemistry: A novel Zn(II)-fluorescent coordination material for highly selective and sensitive detection of Hg2+ ions in aqueous environments

The pursuit of advanced sensing materials for precisely detecting heavy metal ions remains a critical imperative in environmental science. This manuscript deal with a novel fluorescent material, ZU-1, designed for the selective and sensitive detection of Hg2+ ions in aqueous suspension. Employing the Hard-Soft Acid-Base (HSAB) concept, Zn2+ serves as the d10 metal ion, and ZU-1 is synthesized with a −S donor ligand (NaSCN) and 2-pyridine methanol (Hhmp). The fluorescence sensing elucidates a unique detection mechanism, unveiling the distinctive coordination facilitated by the larger ionic radius and soft acid characteristics of Hg2+ with the −S donor sites in ZU-1. Fluorescence titration experiments validate ZU-1’s outstanding ability to selectively quench fluorescence intensity in the presence of Hg2+, even amidst interference from other metal ions. The quantitative analysis yields a Stern-Volmer constant (Ksv) of 7.5 × 108 M−1 and an exceptional limit of detection for Hg2+ at ∼0.60 ppm. ZU-1 further distinguishes itself through outstanding recyclability over four cycles, underscoring its potential as a sustainable and reusable sensor for real-time Hg2+ detection. Beyond its practical implications, this research contributes fundamental insights into design principles for materials exhibiting heightened selectivity and sensitivity to heavy metal ions.

Switching CO2 Electroreduction toward Ethanol by Delocalization State-Tuned Bond Cleavage.

The electrochemical CO2 reduction reaction by copper-based catalysts features a promising approach to generate value-added multicarbon (C2+) products. However, due to the unfavored formation of oxygenate intermediates on the catalyst surface, the selectivity of C2+ alcohols like ethanol remains unsatisfactory compared to that of ethylene. The bifurcation point (i.e., the CH2═CHO* intermediate adsorbed on Cu via a Cu-O-C linkage) is critical to the C2+ product selectivity, whereas the subsequent cleavage of the Cu-O or the O-C bond determines the ethanol or ethylene pathway. Inspired by the hard-soft acid-base theory, in this work, we demonstrate an electron delocalization tuning strategy of the Cu catalyst by a nitrene surface functionalization approach, which allows weakening and cleaving of the Cu-O bond of the adsorbed CH2═CHO*, as well as accelerating hydrogenation of the C═C bond along the ethanol pathway. As a result, the nitrene-functionalized Cu catalyst exhibited a much-enhanced ethanol Faradaic efficiency of 45% with a peak partial current density of 406 mA·cm-2, substantially exceeding that of unmodified Cu or amide-functionalized Cu. When assembled in a membrane electrode assembly electrolyzer, the catalyst presented a stable CO2-to-ethanol conversion for >300 h at an industrial current density of 400 mA·cm-2.

Heterogeneous metallaphotocatalytic Cross-Coupling reactions by a carbon Nitride-Nickel catalyst

The integration of heterogeneous photocatalysts with nickel catalysis is garnering considerable interest for their capacity to enable distinct metal-photoredox processes for organic synthesis. However, the challenge about robustness and recyclability of the photocatalyst persists. Herein, a crystalline carbon nitride (MCN-B) photocatalyst with intentionally introduced defects and a dedicated designed active site has been presented. Results reveal by incorporating the deprotonated cyano-group (N-–CN) sites, this host material could provide stable binding sites for Ni (II) ions through the Hard-Soft Acid-Base (HSAB) effect, thereby facilitating charge transmission between semiconductor and metal centers. Consequently, the integrated carbon nitride nickel (Ni/MCN-B) heterogeneous photocatalyst demonstrates high effectiveness in diverse photocatalytic C-N coupling reactions (21 examples, up to 93% yield) under conditions free from organic ligands and additives, which shows competent performance to the homogeneous catalysts. Moreover, the Ni/MCN-B catalyst demonstrates remarkable recyclability, maintaining its photoredox efficiency after 10 cycles with minimal loss of activity and a diminished metal leaching rate, which signifies a substantial advancement in the field of photocatalytic system design.

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.

Ionization Patterns and Chemical Reactivity of Cytosine-Guanine Watson-Crick Pairs.

Gas-phase and aqueous vertical ionization potentials, vIPgas and vIPaq respectively and measurements of the molecular electrostatic and local ionization maps calculated at the DFT/B3LYP-D3/ 6-311+G** level of theory and the C-PCM reaction field model for single- and double-stranded CpG and 5MeCpG pairs show that the vIPaq for single- and double-stranded pairs of C-G and 5MeC-G are practically the same, in the range of 5.79 to 5.81 eV. The aqueous adiabatic ionization potentials for single-stranded CpG and 5MeCpG are 5.52 eV and 5.51 eV respectively and they reflect the nuclear reorganization that takes place after the abstraction of the electron. The aqueous adiabatic ionization energy values that correspond to the CpG+. radical cation and the hydrated electron, e-,, being at infinite distance, adIPaq+Vo, are 3.92 eV and 3.91 eV respectively with (Vo=-1.6 eV) Analysis of data suggest that the HOMO-LUMO energy gap in the hard/soft-acid/base (HSAB) concept cannot be used a priori to determine the effect of cytosine methylation on the guanine enhanced oxidative damage in DNA.

Leveraging Hard–Soft Acid–Base Interactions for Effective Palladium Capture in Acidic Solutions

Leveraging Hard–Soft Acid–Base Interactions for Effective Palladium Capture in Acidic Solutions

Efficient removal of dibutyl phthalate from transformer oils by iron/activated carbon adsorbent

Capturing dibutyl phthalate (DBP) impurities from transformer oils and purifying them is crucial for maintaining long-term sustainable transformer operation. Furthermore, this process significantly reduces the generation of waste from aged transformer oils, thereby contributing to environmental protection and sustainable development. In this study, various metal ion-modified wood activated carbons (ACs) were prepared using the wet impregnation method. The adsorption isotherms and adsorption kinetics studies reveal that Fe/AC exhibits a significant enhancement of more than 40% in DBP adsorption capacity compared to the original AC. Consequently, Fe/AC is the material with the highest adsorption capacity for DBP in transformer oils up to now. Furthermore, the desorption activation energy of DBP on Fe/AC was 46.623 kJ/mol, 1.73 times higher than original AC. Ultimately, the adsorption mechanism was explained using the Hard-Soft-Acid-Base (HSAB) principle, which demonstrated a stronger interaction between hard base DBP and Fe/AC due to the hard acidic nature of Fe3+ and therefore a higher capture capacity of DBP by Fe/AC. The simplified preparation method and enhanced adsorption capacity of the modified Fe/AC make it an efficient and cost-effective approach to ensure reliable and sustained transformer operation, while also minimizing the generation of waste transformer oils.

Probing the Structural Degradation of CsPbBr3 Perovskite Nanocrystals in the Presence of H2O and H2S: How Weak Interactions and HSAB Matter.

Structural degradation of all inorganic CsPbBr3 in the presence of moisture is considered as one of its major limitations to use as an active component in various light-harvesting and light-emitting devices. Herein, we used two similar molecules, H2O and H2S, with similar structures, to follow the decomposition mechanism of CsPbBr3 perovskite nanocrystals. Interestingly, H2O acts as a catalyst for the decomposition of CsPbBr3, which is in contrast to H2S. Our experimental observations followed by density functional theory (DFT) calculations showed that the water molecule is intercalated in the CsPbBr3 perovskite whereas H2S is adsorbed in the (100) planes of CsPbBr3 by a weak electrostatic interaction. According to Pearson's hard-soft acid-base theory, both cations present in CsPbBr3 prefer soft/intermediate bases. In the case of the water molecule, it lacks a soft base and thus it is not directly involved in the reaction whereas H2S can provide a soft base and thus it gets involved in the reaction. Understanding the mechanistic aspects of decomposition can give different methodologies for preventing such unwanted reactions.

Structure of phytic acid functionalized graphene oxide prepared by hydrothermal method based on aqueous species distribution and the hard-soft acid-base theory

Phytic acid functionalized graphene oxide (PA-GO) has encouraging application in environmental treatment. Herein, structure of PA-GO fabricated by hydrothermal method was inspected. Firstly, the aqueous species distribution and ionization states of phytic acid (PA) and graphene oxide (GO) under varying pH was analyzed according to equilibrium thermodynamics to clarify the primary interacting species involved in PA-GO fabrication. Secondly, the hard-soft acid-base (HSAB) theory and spectroscopic characterizations (XPS, FTIR, Raman, UV–Vis and fluorescent spectra) were employed to elucidate the plausible interactions existing in PA-GO. Thermodynamic deduction indicates, C6H6O24P612- is the dominant species of PA, while –OH and –COO- are the dominant state of graphene oxide groups in PA-GO fabrication system. HSAB theory illuminates, the primary interactions occurs between deprotonated oxygen O(O-) and bridged oxygen O(-O-) of phytic acid with hydroxyl group O(Ar-OH) and π electron of graphene oxide. Moreover, electron flows from GO towards PA to induce energy lowering whereby PA-GO is stabilized. HSAB theory prediction was substantiated by spectroscopic analyses. Furthermore, PA-GO efficiently removes ionic dyes in five consecutive cycles with high adsorption capacity. This work may shed light on the fabrication chemistry of PA-GO framework serving as a potential adsorbent.