Sulfonic Acid-functionalized Ionic Liquids Research Articles

Sulfonic Acid Functionalized Ionic Liquids for Defect Passivation via Molecular Interactions for High-Quality Perovskite Films and Stable Solar Cells.

The high photoelectric conversion efficiency and low cost of perovskite solar cells (PSCs) have further inspired people's determination to push this technology toward industrialization. The high-quality perovskite films and high-efficiency and stable PSCs are the crucial factors. Ionic liquids have been proven to be an effective strategy for regulating high-quality perovskite films and high-performance PSCs. However, the regulation mechanism between ionic liquids and perovskites still needs further clarification. In this study, a novel sulfonic acid-functionalized ionic liquid, 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BSO3HMImOTf), was used as an effective additive to regulate high-quality perovskite films and high-performance devices. Microscopic mechanism studies revealed strong interactions between BSO3HMImOTf and Pb2+ ions as well as halogens in the perovskite. The perovskite film is effectively passivated with the controlled crystal growth, suppressed ion migration, facilitating to the greatly improved photovoltaic performance, and superior long-term stability. This article reveals the regulatory mechanism of sulfonic acid type ionic liquids through testing characterization and mechanism analysis, providing a new approach for the preparation of high-quality perovskite devices.

Synthesis of Se polysaccharide catalyzed by sulfonic acid functionalized ionic liquids: Synergism effect of anion/cation

The rational design and construction of controllable selenylation strategy are important for the study on the structure-activity relationship of Se polysaccharides. Herein, selenized Artemisia sphaerocephala polysaccharides (SePASs) were synthesized by using sulfonic acid functionalized ionic liquids (SFILs) as catalysts in order to study the regulation of the cation/anion constitute on the selenylation efficiency and Se polysaccharide structure. Impressively, SFILs could promote the efficient substitution of seleno-group on the polysaccharide backbone through the synergistic catalysis by cation/anions (Se content up to 5582.7 μg/g). Further, reaction mechanism and potential dissolution effect was supported by DFT calculation and polarized light microscopy. 13C NMR and FT-IR spectra analysis of SePASs exhibited that selenite existed in polysaccharides and the substitution position occured at C-6. SEC-MALLS, monosaccharide composition results revealed that strong acidity of SFILs lead to the driving forces toward low molecular mass polysaccharide fragments and synergistic effect of anion/cations in SFILs (-SO3H group of cations as proton donor, anions as nucleophile) showed regulation on average molecular mass. In addition, the strong attractions between the seleno-groups generated agglomeration of polysaccharide chain, which was proved by applying AFM analysis. Therefore, this work provided a new insight for manipulate Se content and MW of Se polysaccharides.

Sustainable and Reusable Sulfonic Acid-Functionalized Task-Specific Ionic Liquid Catalysts for Multicomponent Reactions. A Review

Improvements in Sustainable Organic Synthesis are usually related to the investigation of less hazardous, non-corrosive and renewable materials, as well as waste prevention, energy efficiency, solvent-free reactions, and the development of efficient reusable catalysts. In this context, multicomponent reactions emerged as important strategies for the rapid and more sustainable synthesis of organic molecules. In addition, the use of task-specific ionic liquids as non-conventional solvents and/or catalysts in multicomponent reactions has recently received great attention, contributing to the development of greener synthetic methodologies. This review describes the studies on the use of structurally diverse homogeneous and heterogeneous sulfonic acid-functionalized task-specific ionic liquids as acidic catalysts for multicomponent reactions applied to the synthesis of nitrogen- and oxygen-based heterocycles, as well as related compounds. The combination of the green credentials of multicomponent reactions and acidic ionic liquids are able to improve process sustainability and green metrics, contributing to sustainable chemical development and, ultimately, to economic growth and cleaner industrial production.

Significant effects of the anion on the catalytic behaviour of sulfonic acid-functionalized ionic liquids in transesterification reactions – A combined electrochemical/catalytic study

• The counterion in sulfonated task-specific ionic liquids affects proton availability. • Protons at ionic liquid bases are more available in chlorides respect to bisulphates. • Chlorides of sulfonated imidazolic bases are intrinsically good acid catalysts. • Transesterification proceeds efficiently using chlorides of protic imidazolic bases. This work studies the strong influence of the counterion on the performance of ionic liquids (ILs) with sulfonic acid-functionalized butyl-imidazolic bases as homogeneous acid catalysts. Through a voltammetric analysis, it was shown that the availability of protons from the sulfonic acid groups in ILs with chloride and bisulphate anions is quite different, thus affecting their intrinsic activity as acid catalysts. The study was focused on the chlorides and bisulphates of 1-(4-sulfonic acid)-butyl-3-methylimidazolium ([bsmim]) and 1-(4-sulfonic acid)-butyl-imidazolium ([bsHim]), and the test reaction to evaluate these ILs as catalysts was the transesterification of p-nitrophenyl acetate with methanol. In ILs with counterion bisulphate, protons at the sulfonic acid groups are deeply involved in building the IL´s H-bonded network, so the acceptable catalytic activity for the tested reaction that was verified on these ILs was mostly sustained by the free sulphuric acid that was always present with the ionic pairs. On the contrary, ILs with chloride counterion conform more loosen networks where protons from the sulfonic acid groups are readily available and allow to efficiently catalyse the reaction, independently of the amounts of free hydrochloric acid that may be along with the ionic pair. Remarkably, the same contrast was verified in the catalytic performances of bisulphate and chloride of the non-sulfonated base 1-butyl-imidazolium ([bHim]), where the imidazolic hydrogen acted as an efficient acid catalyst only in [bHim]Cl.

Insights on the catalytic behaviour of sulfonic acid-functionalized ionic liquids (ILs) in transesterification reactions - voltammetric characterization of sulfonic task-specific ILs with bisulfate anions.

This work shows for the first time the link between the amount of free sulfuric acid (as detected by cyclic voltammetry) and the activity of sulfonic-acid-functionalized ionic liquids (ILs) as acid catalysts for a transesterification reaction, and demonstrates that sulfonic acid groups, while are not directly involved in the catalysis, release the free acid during the reaction. Two imidazolic ILs with bisulfate as the counterion and their corresponding task-specific ILs (TSILs) that resulted from the addition of a sulfonic acid group inside the imidazolic-base structure were studied. The outstanding catalytic activity at room temperature of the TSILs 1-(4-sulfonic acid)-butyl-3-methylimidazolium bisulfate ([bsmim]HSO4) and 1-(4-sulfonic acid)-butyl-imidazolium bisulfate ([bsHim]HSO4) for the transesterification of p-nitrophenyl acetate with methanol was associated to the significant amounts of free sulfuric acid in equilibria with the ionic pairs. It was concluded that these TSILs function as reservoirs for releasing the free acid, which is the actual acid catalyst. In contrast, the corresponding non-sulfonic ILs supply very little amounts of free acid and consequently present low catalytic activities at room temperature, which in fact can be improved by increasing the reaction temperature up to 100 °C.

Porous polymer microsphere functionalized with benzimidazolium based ionic liquids as effective solid catalysts for esterification

Abstract To prepare polymer supported ionic liquids (PSILs) as effective catalysts for esterification, the free radical suspension copolymerization of vinylbenzyl chloride (VBC, monomer), styrene (St, monomer) and divinylbenzene (DVB, crosslinker) with the addition of n-heptane (porogen) was carried out for the fabrication of the porous polymer (PVD) microsphere as support, followed by the immobilization of sulfonic acid-functionalized ionic liquids by the successive treatment of benzimidazole (BIm), 1,3-propane sultone and sulfuric acid (H2SO4) or trifluoromethanesulfonic acid (CF3SO3H). The effects of the compositions of DVB and n-heptane on the internal structure of the polymer supports were investigated, and it was found that the support with 40 wt% DVB and 60 wt% n-heptane (with relative to the monomer) could endow the final PSILs with the relatively optimal catalytic performance. The preliminary experiment in the batch reactor indicated that PSILs herein exhibited higher catalytic activities than commercial Amberlyst 46 resin for the esterification of propanoic acid (PROAc) with n-propanol (PROOH). Consequently, the optimal PSILs catalyst, PVD-[Bim-SO3H]HSO4, was selected for further study in the batch reactive distillation column because of low cost and its ease of preparation. The yield of propyl ropionate (PROPRO) could reach up to 97.78% at the optimized conditions of PROOH/PROAc molar ratio (2:1) and catalyst dosage (2.0 wt%). The investigation of the reaction kinetic manifested that the calculated results of second order pseudo-homogeneous kinetic model were in good agreement with experimental values. The pre-exponential factor and activation energy were 4.12 × 107 L·mol−1·min−1 and 60.57 kJ·mol−1, respectively. It is worth noting that the PSILs catalyst could be simply recovered and reused with relatively satisfactory decrease in the catalytic activity, which made it an environmental friendly and promising catalyst in the industrial application.

Experimental and modeling study of isobutane alkylation with C4 olefin catalyzed by Brønsted acidic ionic liquid/sulfuric acid

As a dual solvent-catalyst, sulfonic-acid-functionalized ionic liquids (SFILs) are promising catalysts for the C4 alkylation. In the present work, the effect of the SFILs with different ratios to the H2SO4 on the catalytic performance and interfacial properties for the H2SO4-catalyzed alkylation was investigated by the combination of experiments and MD simulation. Experimental results indicated that compared to pure H2SO4, the introduction of the SFILs can contribute to a higher selectivity of C8-alkylates as well as Research Octane Number (RON), suggesting a higher quality of alkylate. Moreover, the catalytic performance of the SFIL/H2SO4 catalyst is improved with the increased addition ratio of the SFIL into the H2SO4 within the range of 10 wt%. MD simulation results revealed that the obvious density enrichment of the cations of the SFILs at the interface results in a larger interface width, and higher interface number and better dispersion of C4 hydrocarbons at the interface, which can be ascribed to the location of the alkyl chains close to the C4 hydrocarbon phase with the extended and perpendicular behaviors. The improvement of interfacial properties due to the addition of the SFILs is favorable to the enhancement of the quality of alkylate, which is in excellent agreement with experimental results. Hopefully, the useful information in this work can provide a reference to the design of the SFILs and the optimization of the C4 alkylation process.

One-pot conversion of cyclohexanol to ɛ-caprolactam using a multifunctional Na2WO4-acidic ionic liquid catalytic system

Na2WO4-acidic ionic liquid was used as a simple, ecofriendly, recyclable and efficient catalytic system for the one-pot conversion of cyclohexanol to ɛ-caprolactam. The effect of the structure of the ionic liquid on the catalytic activity of this system was investigated, and the results revealed that sulfonic acid-functionalized ionic liquids with HSO4− as an anion gave the best results. The highly efficient performance of this catalyst system was attributed to the phase-transfer behavior of the cation of the ionic liquid, the improved coordination of the substrate to bisperoxotungstate during the oxidation reaction, and the stabilization of the intermediate formed during the Beckmann rearrangement.

Ionic Liquid–Silicotungstic Acid Composites as Efficient and Recyclable Catalysts for the Selective Esterification of Glycerol with Lauric Acid to Monolaurin

AbstractThe synthesis of glycerol monolaurate (GML) by the esterification of glycerol (GL) with lauric acid (LA) over a series of propyl sulfonic acid‐functionalized ionic liquids (SAFILs)‐modified silicotungstic acid (STA; H4SiW12O40) composite catalysts has been investigated. The synthesized organic–inorganic hybrid catalysts were characterized by different physicochemical techniques. In particular, their acidic properties were studied by solid‐state 31P magic angle spinning (MAS) NMR spectroscopy by using adsorbed trimethylphosphine oxide (TMPO) as a probe. The effects of key reaction parameters, such as glycerol/lauric acid molar ratio, amount of catalyst, reaction time, and reaction temperature on LA conversion and GML product yield were elucidated and optimized with response surface methodology (RSM). The N,N‐dimethyl(benzyl)ammonium propyl sulfobetaine (DMBPS)‐modified STA [DMBPSH]H3SiW12O40 exhibited the optimal catalytic activity and was exploited for process optimization. A highest GML yield of 79.1 % was achieved with the optimized reaction conditions. The high catalytic activity of these hybrid catalysts were attributed to strong acidity, low transport resistance, and their “pseudoliquid” characteristics. A kinetic study was made based on a second‐order irreversible model of the esterification reaction, which resulted in an activation energy of 39.49 kJ mol−1 for [DMBPSH]H3SiW12O40 under optimized reaction conditions.

Proton Microenvironment and Interfacial Structure of Sulfonic-Acid-Functionalized Ionic Liquids

Sulfonic-acid-functionalized ionic liquids (SFILs) have shown promising performance in catalytic reactions and development of new proton conductive materials. In this work, molecular dynamic simulation based on the ion pair charge approach has been performed to investigate the structural characteristic of several typical SFILs in both bulk liquids and the vacuum–liquid interfacial region. The results showed that anions play a critical role in determining the microenvironment of the terminal sulfonic acid proton in SFILs, and less basic anions lead to a much weaker association of sulfonic acid protons with anions. A significant aggregation of sulfonic acid side chains existed in SFILs because of the strong interaction between different sulfonic acid groups. A sharp change in the ordering preference of alkyl tails and pyridine rings at vacuum–liquid interfaces was observed after the introduction of a sulfonic acid group to the side chain of the cation of ionic liquids, and the properties of the anions have ...

Mechanistic study for the formation of polyoxymethylene dimethyl ethers promoted by sulfonic acid-functionalized ionic liquids

Polyoxymethylene dimethyl ethers (DMMn), which are ideal additives for diesel fuel, are mainly synthesized from the condensation of methanol (MeOH) or dimethoxymethane (DMM) with 1,3,5-trioxane (TOX) or paraformaldehyde (PF) promoted by different acid catalysts. However, up to date, few studies have been reported to examine the formation mechanism of DMMn which is essential in understanding the reaction and valuable in designing improved catalysts. In this work, using the density functional theory (DFT) calculations combined with experiment studies, we evaluate the formation mechanism of DMMn which is promoted by sulfonic acid-functionalized ionic liquids (SO3H-FILs). Our calculated results indicate TOX and PF should dissociate into formaldehyde monomers firstly and then to react with MeOH or DMM. However, their decomposition process is different where the dissociation of TOX proceeds along a two-step mechanism while it follows a one-step mechanism for PF dissociation. As for the formation of DMMn, the reaction proceeds along a hemiacetal-carbocation pathway when MeOH is selected as the capping group provider, while the reaction follows a carbocation pathway when DMM is chosen. The origination for the product distribution pattern has also been discussed in detail. The cations and anions of ionic liquids are found synergistically promote the condensation reaction by proton transfer and simultaneously stabilizing the formed intermediated and transition states. Moreover, all the processes related to the decomposition of TOX and PF and the condensation reaction are reversible.

An efficient and highly selective ortho-tert-butylation of p-cresol with methyl tert-butyl ether catalyzed by sulfonated ionic liquids

A novel series of sulfonic acid-functionalized ionic liquids (SFILs) was found to act as efficient catalysts for ortho-tert-butylation of p-cresol with methyl tert-butyl ether (MTBE) as the tert-butylating agent without an added solvent. The mono o-tert-butylated product was obtained in up to 80.4% isolated yield and 95.2% selectivity under such green conditions. No O-tert-butylated byproducts were formed.

ChemInform Abstract: Sulfonic Acid‐Functionalized Ionic Liquids as Metal‐Free, Efficient and Reusable Catalysts for Direct Amination of Alcohols.

A series of sulfonic acid-functionalized (SO3H-functionalized) ionic liquids was synthesized and used as metal-free, highly selective and efficient catalysts for the direct amination of alcohols. Notably, the activities of the series of SO3H-functionalized ionic liquids were compared and a 92% isolated yield was obtained using 3-tetradecyl-1-(butyl-4- sulfonyl)imidazolium trifluoromethanesulfonate ([BsTdIM][OTf]) as the catalyst. Importantly, the catalytic system has wide substrate scope including benzylic, allyl, propargylic, aliphatic alcohols with sulfonamide, amide, carbamate, aromatic amine and N-heterocyclic compounds. Interestingly, the system was also suitable for a multi-gram scale direct amination of alcohols. Additionally, the reusable nature of [BsTdIM][OTf] makes this protocol more attractive and avoids the disposal and neutralization of acidic catalysts. Moreover, preliminary experiments indicated that this reaction should proceed via an SN1 pathway.

A direct synthesis of 5-alkoxymethylfurfural ethers from fructose via sulfonic acid-functionalized ionic liquids

5-Alkoxymethylfurfural ethers are synthesized directly from fructose using ionic liquids (imidazolium propanesulfonic acids) and alcohols in a novel biphasic system.

Hydrolysis of chitosan under microwave irradiation in ionic liquids promoted by sulfonic acid-functionalized ionic liquids

Hydrolysis of chitosan in ionic liquids was carried out under microwave irradiation (MW) using sulfonic acid-functionalized ionic liquids (SFILs) as catalysts. The effect of microwave power, irradiation time, dosage of SFILs and DMSO was investigated by orthogonal tests. Under the optimal reaction conditions, the yield of total reducing sugars (TRS) reached over 90% within 2 min. The viscosity-average molecular weight of degraded chitosan was determined by viscosity method. The structures of the original and degraded chitosan were characterized by Fourier-transform infrared (FTIR) spectra, X-ray powder diffraction (XRD) analysis and carbon-13 nuclear magnetic resonance spectroscopy (13C NMR). The influence of microwave power and irradiation time on the TRS and Mv was further studied. This method can dramatically reduce reaction time.

Synthesis of 4,4′-MDC in the Presence of Sulfonic Acid-functionalized Ionic Liquids

The synthesis of methylene diphenyl dimethylcarbamate (4,4′-MDC) from methyl N-phenyl carbonate (MPC) and formaldehyde (HCHO) was conducted in the presence of sulfonic acid-functionalized ionic liquids (ILs) as dual solvent-catalyst. The influences of the kind of anion in the ionic liquids, reaction conditions and the recycle of the ionic liquid on 4,4′-MDC synthesis reaction were investigated. In addition, the acid strength of ILs was determined by the Hammett method with UV-visible spectroscopy, and the acid strength-catalytic activity relationship was correlated. The activity estimation results showed that [HSO 3-bmim]CF 3SO 3 was the optimal dual solvent-catalyst. Under the suitable reaction conditions of 70°C, 40 min, molar ratio of n MPC/ n HCHO10/1 and mass ratio of W ILs/ W MPC4.5/1, the yield of 4,4′-MDC based on HCHO was 89.9 % and the selectivity of 4,4′-MDC with respect to MPC was 74.9%. Besides, [HSO 3-bmim]CF 3SO 3 was reused four times after being purified and no significant loss in the catalytic activity was observed.

Nitration of aromatic compounds with NO2/air catalyzed by sulfonic acid-functionalized ionic liquids

Nitration of aromatic compounds with NO 2 /air catalyzed by sulfonic acid-functionalized ionic liquid under solvent-free conditions is reported. A variety of ionic liquids [BSPy][HSO 4 ], [BSPy][TfO], and [BSPy][pTSA] ([BSPy] = N -(4-hydroxsulfonylbutyl) pyridinium) were prepared. Their acidities were further investigated by Hammett method and the acidity-catalytic relationship was discussed. It was found that satisfactory results were obtained with [BSPy][HSO 4 ]. Ionic liquids could be conveniently separated with the products and reused for five times with excellent yield of mono-nitration products and para-selectivity.

The sulfonic acid-functionalized ionic liquids with pyridinium cations: Acidities and their acidity–catalytic activity relationships

The Brønsted acidities of sulfonic acid-functionalized ionic liquids (SFILs) with pyridinium cations were investigated. The Hammett function values of SFILs are between −1.5 and −3.6 at 110 °C. The acidities of SFILs depend on the anions, and have the order as follows: [PSPy][BF 4] > [PSPy][HSO 4] > [PSPy][ pTSA] > [PSPy][H 2PO 4] ([PSPy] = N-propane–sulfonic acid pyridinium). The acidity order of SFILs is consistent with their activity order observed in some acid-catalyzed reactions. The minimum-energy geometries of SFILs manifest that anions have strong interactions with the sulfonic acid proton. It is considered that in addition to the alkyl sulfonic acid group, the anion is likely to serve as available acid sites. Hence the acidities and catalytic activities of SFILs depend on the kinds of anions.