Waste-derived carbon nanostructures (WD-CNs): An innovative step toward waste to treasury

With the growing population, the accumulation of waste materials (WMs) (industrial/household waste) in the environment incessantly increases, affecting human health. Additionally, it affects the climate and ecosystem of terrestrial and water habitats, thereby needing effective management technology to control environmental pollution. In this aspect, managing these WMs to develop products that mitigate the associated issues is necessary. Researchers continue to focus on WMs management by adopting a circular economy. These WMs convert into useful/value-added products such as polymers and nanomaterials (NMs), especially carbon nanomaterials (CNs). The conversion/transformation of waste material into useful products is one of the best solutions for managing waste. Waste-derived CNs (WD-CNs) have established boundless promises for numerous applications like environmental remediation, energy, catalysts, sensors, and biomedical applications. This review paper discusses the several sources of waste material (agricultural, plastic, industrial, biomass, and other) transforming into WD-CNs, such as carbon nanotubes (CNTs), biochar, graphene, carbon nanofibers (CNFs), carbon dots, etc., are extensively elaborated and their application. The impact of metal doping within the WD-CNs is briefly discussed, along with their applicability to end applications.

Magnetic Ionic Liquids: Current Achievements and Future Perspectives with a Focus on Computational Approaches

Magnetic ionic liquids (MILs) stand out as a remarkable subclass of ionic liquids (ILs), combining the desirable features of traditional ILs with the unique ability to respond to external magnetic fields. The incorporation of paramagnetic species into their structures endows them with additional attractive features, including thermochromic behavior and luminescence. These exceptional properties position MILs as highly promising materials for diverse applications, such as gas capture, DNA extractions, and sensing technologies. The present Review synthesizes key experimental findings, offering insights into the structural, thermal, magnetic, and optical properties across various MIL families. Special emphasis is placed on unraveling the influence of different paramagnetic species on MILs' behavior and functionality. Additionally, the Review highlights recent advancements in computational approaches applied to MIL research. By leveraging molecular dynamics (MD) simulations and density functional theory (DFT) calculations, these computational techniques have provided invaluable insights into the underlying mechanisms governing MILs' behavior, facilitating accurate property predictions. In conclusion, this Review provides a comprehensive overview of the current state of research on MILs, showcasing their special properties and potential applications while highlighting the indispensable role of computational methods in unraveling the complexities of these intriguing materials. The Review concludes with a forward-looking perspective on the future directions of research in the field of magnetic ionic liquids.

Organometallic Ionic Liquids Containing Sandwich Complexes: Molecular Design, Physical Properties, and Chemical Reactivities

Ionic liquids (ILs) are salts with low melting points and are useful as electrolytes and solvents. We have developed ILs containing cationic metal complexes, which form a family of functional liquids that exhibit unique physical properties and chemical reactivities originating from metal complexes. Our study explores the liquid chemistry in the field of coordination chemistry, where solid-state chemistry is currently the main focus. This review describes the molecular design, physical properties, and reactivities of organometallic ILs containing sandwich or half-sandwich complexes. This paper mainly covers stimuli-responsive ILs, whose magnetic properties, solvent polarities, colors, or structures change by the application of external fields, such as light, heat, and magnetic fields, or by reaction with coordinating molecules.

Tuning Ionic Liquid-Based Catalysts for CO2 Conversion into Quinazoline-2,4(1H,3H)-diones

Carbon capture and storage (CCS) and carbon capture and utilization (CCU) are two kinds of strategies to reduce the CO₂ concentration in the atmosphere, which is emitted from the burning of fossil fuels and leads to the greenhouse effect. With the unique properties of ionic liquids (ILs), such as low vapor pressures, tunable structures, high solubilities, and high thermal and chemical stabilities, they could be used as solvents and catalysts for CO₂ capture and conversion into value-added chemicals. In this critical review, we mainly focus our attention on the tuning IL-based catalysts for CO₂ conversion into quinazoline-2,4(1H,3H)-diones from o-aminobenzonitriles during this decade (2012~2022). Due to the importance of basicity and nucleophilicity of catalysts, kinds of ILs with basic anions such as [OH], carboxylates, aprotic heterocyclic anions, etc., for conversion CO₂ and o-aminobenzonitriles into quinazoline-2,4(1H,3H)-diones via different catalytic mechanisms, including amino preferential activation, CO₂ preferential activation, and simultaneous amino and CO₂ activation, are investigated systematically. Finally, future directions and prospects for CO₂ conversion by IL-based catalysts are outlined. This review is benefit for academic researchers to obtain an overall understanding of the synthesis of quinazoline-2,4(1H,3H)-diones from CO₂ and o-aminobenzonitriles by IL-based catalysts. This work will also open a door to develop novel IL-based catalysts for the conversion of other acid gases such as SO₂ and H₂S.

Physico-Chemical Properties of Magnetic Dicationic Ionic Liquids with Tetrahaloferrate Anions

A series of imidazolium-based symmetrical and asymmetrical dicationic ionic liquids (DcILs) with alkyl spacers of different length and with [FeCl3 Br]- as counter ion have been synthesized. The synthesized DcILs are characterized by using FTIR and Raman spectroscopy as well as mass spectrometry, along with single-crystal XRD analysis. Physicochemical properties such as solubility, thermal stability and magnetic susceptibility are also measured. These compounds show low melting points, good solubility in water and organic solvents, thermal stability, and paramagnetism. The products of molar susceptibility and temperature (χmol ⋅T) for the synthesized DcILs have been found between 4.05 to 4.79 emu mol-1  K Oe-1 and effective magnetic moment values have also been determined to be compared to that expected from the spin-only approximation.

Thermal Properties and Solvent Polarities of Mixed-Valence Ionic Liquids Containing Cationic Biferrocenylene Derivatives

Ionic liquids (ILs) containing cationic mixed-valence biferrocenylene derivatives were synthesized with an octanoyl or octyl substituent in each cation. Their melting points ranged between 25 and 39 °C, and the octanoyl derivatives exhibited higher melting points than the octyl derivatives. In addition, each IL exhibited a glass transition in the temperature ranging from -66 to -45 °C after melting. Their melting points were ∼10 °C higher than those of mononuclear octamethylferrocenium salts bearing the same substituents. The solvent polarity (E_T^N) and Kamlet-Taft parameters (π*, α, and β) of these dinuclear and mononuclear ILs were then examined. The dinuclear ILs bearing octanoyl substituents exhibited significant increases in E_T^N and π* and a decrease in α with the decreasing temperature, whereas the other ILs exhibited a significantly less pronounced temperature dependence. Finally, the intervalence charge-transfer (or charge-resonance) bands of the octanoyl dinuclear ILs exhibited red shifts with the decreasing temperature, which can be regarded as self-thermosolvatochromism.

The interactions of chelate-based ionic liquids: from the perspective of vaporization enthalpy

The vaporization enthalpies of [C_nTPP][Cu(F₆-acac)₃] (n = 14, 16) and [C_nmim][Cu(F₆-acac)₃] (n = 8, 10), a new type of chelate-based ionic liquids (ChILs), were measured by thermogravimetric analysis (ΔglHom(T_av) = 73.2-83.7 kJ mol^-1), which decreased compared to their non-chelate counterparts (difference up to 34.1 kJ mol^-1). This can be explained by the fact that the increase in the polar region size by chelate ions mainly leads to the decrease in Coulomb forces based on the micro-biphasic separation in ionic liquids. Vaporization enthalpies at experimental temperatures were adjusted to a reference temperature by the Verevkin's method, and compared with the data calculated by the Kabo's method, which illustrated clear differences on ChILs. In addition, some physicochemical properties of [C_nTPP][Cu(F₆-acac)₃] (n = 14, 16) were measured including density, viscosity, conductivity, and surface tension.

Review on upgrading organic waste to value-added carbon materials for energy and environmental applications

Value-added materials such as biochar and activated carbon that are produced using thermo-chemical conversion of organic waste have gained an emerging interest for the application in the fields of energy and environment because of their low cost and unique physico-chemical properties. Organic waste-derived materials have multifunctional abilities in the field of environment for capturing greenhouse gases and remediation of contaminated soil and water as well as in the field of energy storage and conversion. This review critically evaluates and discusses the current thermo-chemical approaches for upgrading organic waste to value-added carbon materials, performance enhancement of these materials via activation and/or surface modification, and recent research findings related to energy and environmental applications. Moreover, this review provides detailed guidelines for preparing high-performance organic waste-derived materials and insights for their potential applications. Key challenges associated with the sustainable management of organic waste for ecological and socio-economic benefits and potential solutions are also discussed.

Special Mixing Behavior of Chelate-based Ionic Liquid with Methanol

Compared to the general ionic liquids (ILs), a significant deviation of the binary mixtures of 1-decyl-3-methylimidazolium tri(hexafluoroacetylaceto)-copper(II) ([C₁₀ mim][Cu(hfacac)₃ ]) with methanol was found, indicating the way methanol interacts with ILs might be governed by the special structure of the chelating anion. IR results showed that the v (C2-H) of 1-decyl-3-methylimidazolium hexafluoroacetylacetonate ([C₁₀ mim][hfacac]) blue-shifted more significantly than that of [C₁₀ mim][Cu(hfacac)₃ ], meanwhile the v (C=O) red-shifted in [C₁₀ mim][Cu(hfacac)₃ ], which is contrast with that in [C₁₀ mim][hfacac]. Two-dimensional correlation analysis of the FTIR spectra indicated that the chelating cavity has little effect on the sequence of the ILs sites that interact with methanol. Combined with small angle X-ray scattering (SAXS) results, the picture of mixing processes in these two systems were proposed. Methanol interacts directly with the anion followed by the cation in [C₁₀ mim][hfacac], while methanol preferentially enters the chelating cavity and enhances the packing effect in the [C₁₀ mim][Cu(hfacac)₃ ] system.

Photoinduced and Thermal Linkage Isomerizations of an Organometallic Ionic Liquid Containing a Half-Sandwich Ruthenium Thiocyanate Complex

Metal complexes with thiocyanate (SCN^-) ligands typically exhibit S- or N-coordinated linkage isomers. In this study, to explore ionic liquids that exhibit stimuli-responsiveness based on linkage isomerization, we synthesized an ionic liquid containing a cationic half-sandwich thiocyanate complex, [Ru(C₆H₆)(NCS)L]Tf₂N (L = N-hexyl-2-pyridinemethanimine, Tf₂N = bis(trifluoromethanesulfonyl)amide anion). The as-synthesized ionic liquid was a 0.7:0.3 mixture of N- and S-coordinated isomers, presenting as an extremely viscous liquid exhibiting a glass transition at 0 °C. Isomerization from the N- to the S-coordinated isomer occurred upon UV photoirradiation or heating, although thermal isomerization was accompanied by significant decomposition. The N- and S-coordinated isomers were separated into brown and orange liquids, respectively, using gel permeation chromatography. Each isomer exhibited a small solvatochromic absorption shift in organic solvents, with different solvent dependences observed for the two isomers.

Metal-Based Ionic Liquids in Oxidative Desulfurization: A Critical Review

Ionic liquids (ILs) as novel functional desulfurization materials have attracted increasing attentions. Metal-based ionic liquids (MILs) are classified into three types of metal chloride ILs, metal oxide ILs, and metal complex ILs based on the definition and basic structure of MILs in this critical review. On the basis of the properties of ILs such as structure designability, super dissolution performance, good thermal and chemical stability, nonflammability, and wide electrochemical window, MILs exhibit unique advantages on hydrophobicity, oxidation performance, and Brönsted-Lewis acidity. Therefore, MILs possess both the absorption and oxidation centers for the intramolecular adsorption and oxidation to improve the oxidative desulfurization (ODS) process. During the novel nonaqueous wet oxidative desulfurization process (Nasil), H₂S can be oxidized into elemental sulfur with hydrophobic MILs, which can be regenerated by oxygen for recycle, to solve the problems of low sulfur capacity, low sulfur quality, and severe secondary pollution in the aqueous Lo-Cat wet oxidative desulfurization process. Another outstanding feature of MILs in ODS is biomimetic catalysis, which has the function of activating molecular oxygen and improving the oxidation performance. Metal oxide ILs and metal complex ILs are used in combination with hydrogen peroxide or oxygen with the existing water to generate a Fenton-like reaction to convert hydrophobic organic sulfur or SO₂ into hydrophilic sulfoxide/sulfone or sulfur acid, respectively. However, the corrosion of Cl^- to the equipment and emulsification phenomenon in the extraction process of sulfoxide/sulfone separation still need further study. Furthermore, the promising strategies to construct highly efficient and green desulfurization processes for large-scale applications are provided.

A magnetically retrievable copper ionic liquid nanocatalyst for cyclooxidative synthesis of 2-phenylquinazolin-4(3H)-ones

In the present work, we report the design and fabrication of a copper-containing ionic liquid supported magnetic nanocatalyst via a convenient and straightforward synthetic approach for the formation of 2-phenylquinazolin-4(3H)-ones using o-aminobenzamide and benzaldehydes as the reaction partners. The successful formation and properties of the as-prepared catalyst have been thoroughly investigated using diverse physico-chemical techniques including FT-IR, XRD, FE-SEM, TEM, ICP, VSM, BET and TGA. Using this nanocatalytic system, a variety of 2-phenylquinazolin-4(3H)-ones are synthesized in excellent yields with operational ease and short reaction times in an environmentally preferable solvent under open air and without using any external oxidizing agent. Besides, the catalyst possessed facile magnetic recoverability and remarkable reusability for six consecutive runs without any appreciable decrease in the catalytic efficiency.

Structural and electronic properties of CuII, CoII, and NiII-containing chelate-based ionic liquids

Potential applications of chelate-based ionic liquids depend on the structural and electronic properties of this class of liquid materials. Due to the large size of chelated metal anions, the high number of potential interaction sites could lead to complex intermolecular interactions, but metal-based anions have many degrees of freedom, and they have great potential in the structural modification of the physical properties of ionic liquids. To explore the influence of varying the metal center of anions and the length of carbon chains of cationic species, four single crystal structures of chelate-based ionic liquids, ([C₁₀mim][M(F₆-acac)₃], M = Cu, Co, and Ni) and [C₆mim][Cu(F₆-acac)₃] were obtained. Taking these as the initial configurations, theoretical efforts were made to understand the structural and electronic properties. The hydrogen bonding energies of the primary hydrogen bonding interaction, in the range of 17.7-20.9 kJ mol^-1, follow the order of [C₁₀mim][Ni(F₆-acac)₃] < [C₁₀mim][Co(F₆-acac)₃] <[C₁₀mim][Cu(F₆-acac)₃], and [C_nmim][Cu(F₆-acac)₃] (n≠ 10) < [C₁₀mim][Cu(F₆-acac)₃], while the experimental viscosities exhibit an opposite trend. Furthermore, by NBO analysis, the more negative charge on the oxygen atoms of anions shows the stronger hydrogen bonding of imidazolium with C²H. The reliability of the theoretical method was supported by the comparison between the simulated and experimental infrared and UV/vis spectra. This work is useful in increasing the understanding of the structure-property relationship of chelate-based ionic liquids and furthering the rational design of novel ionic liquids.

Synthesis of Guerbet ionic liquids and extractants as β-branched biosourceable hydrophobes

This study investigates the synthesis of β-branched amines and β-branched quaternary ammonium chloride ionic liquids as novel extractants. The synthesis methodology was tailored to facilitate the reaction scale-up and the use of biorenewable starting materials. The developed process is an overall green, easy and straightforward synthesis of β-branched amines, and ammonium salts, starting from linear aldehydes. In order to evaluate the potential of the synthesised materials in applications, the rheology, density, thermal stability, chemical stability, phase transitions, and mutual solubility with water of the novel extractants was studied.

Heterogeneous photocatalytic performances of CO2 reduction based on the [Emim]BF4 + TEOA + H2O system

The photochemical reduction of CO2 was studied in a 1-ethyl-3-methylimidazolium tetrafluoroborate, triethanolamine and water ([Emim]BF4 + TEOA + H2O) system under visible light irradiation. The integration of CdS and the Co-bpy complex, which acted as a photocatalyst and cocatalyst, respectively, was employed as an efficient catalytic system for the CO2-to-CO conversion. The utilization of [Emim]BF4 and water took advantage of their green properties. The amount of CO production showed that the test medium containing 10 vol% H2O was favourable for the catalytic performance of the CO2 reduction. In order to further study the factors that influenced the current system, the physical and spectroscopy properties were characterized by altering the composition ratio of the ingredients. Relevant parameters, including the viscosity, conductivity, solubility and coordination, were adjusted using the ratio of the H2O/[Emim]BF4 addition, resulting in a different catalytic performance. All of these attempts led to an optimal reaction condition for the CO2 reduction process.

Maximizing Ion-Tagged Oligonucleotide Loading on Magnetic Ionic Liquid Supports for the Sequence-Specific Extraction of Nucleic Acids

Targeted nucleic acid analysis requires the highly selective extraction of desired DNA fragments in order to minimize interferences from samples with abundant heterogeneous sequences. We previously reported a method based on functionalized oligonucleotide probes known as ion-tagged oligonucleotides (ITOs) that hybridize with complementary DNA targets for subsequent capture using a hydrophobic magnetic ionic liquid (MIL) support. Although the ITO-MIL approach enriched specific DNA sequences in quantities comparable to a commercial magnetic bead-based method, the modest affinity of the ITO for the hydrophobic MIL limited the yield of DNA targets, particularly when stringent wash conditions were applied to remove untargeted DNA. Here, we report the synthesis and characterization of a series of ITOs in which functional groups were installed within the cation and anion components of the tag moiety in order to facilitate loading of the ITO to the MIL support phase. In addition to hydrophobic interactions, we demonstrate that π-π stacking and fluorophilic interactions can be exploited for loading oligonucleotide probes onto MILs. Using a disubstituted ion-tagged oligonucleotide (DTO) possessing two linear C₈ groups, nearly quantitative loading of the probe onto the MIL support was achieved. The enhanced stability of the DTO within the MIL solvent permitted successive wash steps without the loss of the DNA target compared to a monosubstituted ITO with a single C₈ group that was susceptible to increased loss of analyte. Furthermore, the successful capture of a 120 bp KRAS fragment from human plasma samples followed by real-time quantitative polymerase chain reaction (qPCR) amplification is demonstrated.

Investigating the effect of ligand and cation on the properties of metal fluorinated acetylacetonate based magnetic ionic liquids

The effect of chemical structure on various physiochemical properties including thermal stability, solvent miscibility, magnetic susceptibility and viscosity is studied for acetylacetone based magnetic ionic liquids.

Expanding the Structural Motif Landscape of Heterometallic β-Diketonates: Congruently Melting Ionic Solids

The first example of ionic β-diketonates in which both the cation and anion are octahedral coordinatively saturated metal diketonate moieties are reported. Heterometallic tin-transition-metal heteroleptic diketonates were obtained through solid-state redox reactions and are formulated as {[Sn^IV(thd)₃]⁺[M^II(hfac)₃]^-} (M^II = Mn (1), Fe (2), Co (3); thd = 2,2,6,6-tetramethyl-3,5-heptanedionate, hfac = hexafluoroacetylacetonate). X-ray single-crystal structural investigations along with DART mass spectrometry, multinuclear NMR, and magnetic susceptibility measurements have been used to confirm an assignment of metal oxidation states in compounds 1-3. Ionic compounds were found to melt congruently at temperatures below the decomposition point. As such, they represent prospective materials that can be utilized as ionic liquids as well as reagents for the soft transfer of diketonate ligands. An unexpected volatility of ionic compounds 1-3 was proposed to occur through a transport reaction, in which the transport agent is one of the products of their partial decomposition in the gas or condensed phase.

Solvate and protic ionic liquids from aza-crown ethers: synthesis, thermal properties, and LCST behavior

In recent years, solvate and protic ionic liquids (ILs) have attracted much attention. We synthesized both types of ILs from alkyl aza-crown ethers (L = N-propyl-1-aza-15-crown-5 (L¹) and N-C₆F₁₃C₂H₄-1-aza-15-crown-5 (L²)). The solvate ILs [ML][Tf₂N] (M = Na⁺, K⁺) were solids (T_m = 58-68 °C), whereas the solvate ILs [ML][Tf₂N] (M = Li⁺, Ag⁺) and protic ILs [HL][Tf₂N] were liquids with low glass transition temperatures. The ILs containing Na ions were more crystalline and exhibited higher melting points than the other ILs. The decomposition temperatures of the protic ILs were higher than those of the solvate ILs. A protic IL with a paramagnetic anion, [HL¹][FeCl₄] (T_m = 70.5 °C), was also synthesized and its crystal structure was determined. The solvate ILs [NaL²][X] (X = Cl^-, CF₃CO₂^-, TsO^-, PhSO₃^-) exhibited a lower critical solution temperature (LCST)-type behavior in water. The effects of salt addition on the LCST of L² were also investigated. The LCST of these ILs generally increased with increasing hydrophilicity or basicity of the counter anion. This tendency, which is nearly opposite to that of ILs with quaternary onium cations, is ascribed to the amphiphilic nature of the cation. The corresponding protic ILs did not exhibit LCST behavior.

Effect of substituents and anions on the phase behavior of Ru(ii) sandwich complexes: exploring the boundaries between ionic liquids and ionic plastic crystals

We recently developed ionic liquids containing cationic sandwich complexes. However, salts of the sandwich complexes often exhibit ionic plastic phases with high melting points. To explore the boundaries between ionic liquids and plastic crystals of sandwich salts, we investigated, in detail, the phase behavior of ruthenium complexes [Ru(C₅H₅)(C₆H₅R)][X] ([C0][X]: R = H, [C1][X]: R = Me, [C2][X]: R = Et, [C4][X]: R = Bu). Among salts containing the anions PF₆^-, FSA^-, and B(CN)₄^-, [C0][X] and [C1][X] are solids that exhibit plastic phases at or above room temperature, whereas [C2][X] and [C4][X] are mostly ionic liquids. Salts containing the C(CN)₃^- anion exhibited lower melting points than the other salts. X-ray crystallography reveals that the cations and anions in most of these salts are arranged alternately in the solid state. However, in the case of [C0][C(CN)₃], the cations and anions are stacked independently, thereby providing weaker cation-anion interactions that account for the relatively low melting point of this salt.

Empirical study of physicochemical and spectral properties of CuII-containing chelate-based ionic liquids

The structure–property relations of chelate-based ionic liquids were systematically explored through the study of physicochemical and spectral properties.

Towards ionic liquids with tailored magnetic properties: bmim+ salts of ferro- and antiferromagnetic CuII3 triangles

With proper selection of counteraction and pH control, CuII3-pyrazolate anions can form a ferromagnetic low-melting solid, or an antiferromagnetic viscous paste.

Synthesis and characterization of low viscosity hexafluoroacetylacetonate-based hydrophobic magnetic ionic liquids

The properties of low viscosity, hydrophobic magnetic ionic liquids featuring transition and rare earth metal hexafluoroacetylacetonate chelated anions paired with the trihexyl(tetradecyl)phosphonium cation are studied.

Dye-sensitized solar cells based on cobalt-containing room temperature ionic liquid redox shuttles

An imidazolium-type co-containing ionic liquid, [BMIm]₂[Co(NCS)₄], was synthesized and applied as a redox shuttle for dye-sensitized solar cells.

Structures and Electronic Properties of Lithium Chelate-Based Ionic Liquids

The conformations, electronic properties, and interaction energies of four chelate-based ionic liquids [Li(EA)][Tf2N], [Li(HDA)][Tf2N], [Li(DEA)][Tf2N], and [Li(DOBA)][Tf2N] have been theoretically explored. The reliability of the located conformers has been confirmed via the comparison between the simulated and experimental infrared spectra. Our results show that the N-Li and O-Li coordinate bonds in cation are elongated as the numbers of coordinate heteroatoms of alkanolamine ligands to Li(+) increased. Also the binding energies between Li(+) and ligands are increased and the interaction energies between cations and Tf2N anion are decreased. The cation-anion interaction energies follow the order of [Li(DOBA)][Tf2N] < [Li(HDA)][Tf2N] < [Li(DEA)][Tf2N] < [Li(EA)][Tf2N], which fall within the energetic ranges of conventional ionic liquids. Interestingly, the strongest stabilization orbital interactions in these ionic liquids and their cations revealed by the natural bond orbital analysis lie in the interaction between the lone pair (LP) of the coordinate heteroatoms in ligands or anion as donors and the vacant valence shell nonbonding orbital (LP*) of Li(+) as acceptors, which are very different from that of conventional ionic liquids. Moreover, the charges transferred from cations to anion are quite similar, and the charge of Li(+) is proposed for possibly predicting the order of the interaction energies of ionic liquids in series. The present study allows for the deeper understanding the differences between chelate-based ionic liquids and conventional ionic liquids.