Cationic Ring Research Articles

Molecular Insights into the Binding Behavior of Imidazolium Ionic Liquids to the Receptor Binding Domain of the SARS-CoV-2 Spike Protein.

The receptor-binding domain (RBD) of the SARS-CoV-2 spike protein is considered as a key target for the design and development of COVID-19 drugs and inhibitors. Due to their unique structure and properties, ionic liquids (ILs) have many special interactions with proteins, showing great potential in biomedicine. Nevertheless, few research studies have been carried out on ILs and the spike RBD protein. Here, we explore the interaction of ILs and the RBD protein through large-scale molecular dynamics simulations (4 μs in total). It was found that IL cations with long alkyl chain lengths (nchain) could spontaneously bind to the cavity region of the RBD protein. The longer the alkyl chain is, the stabler the cations bind to the protein. The binding free energy (ΔG) had the same trend, peaking at nchain = 12 with -101.19 kJ/mol. The cationic chain lengths and their fit to the pocket are decisive factors that influence the binding strength of cations and proteins. The cationic imidazole ring has a high contact frequency with phenylalanine and tryptophan, and the hydrophobic residues phenylalanine, valine, leucine, and isoleucine are the most interacting residues with side chains of cations. Meanwhile, through analysis of the interaction energy, the hydrophobic and π-π interactions are the main contributors to the high affinity between cations and the RBD protein. In addition, the long-chain ILs would also act on the protein through clustering. These studies not only provide insights into the molecular interaction between ILs and the RBD of SARS-CoV-2 but also contribute to the rational design of IL-based drugs, drug carriers, and selective inhibitors as a therapeutic for SARS-CoV-2.

Trace Water Effects on Crystalline 1-Ethyl-3-methylimidazolium Acetate.

Spontaneous room-temperature crystallization of 1-ethyl-3-methylimidazolium acetate ([C2mim][OAc]) was observed upon removal of trace water. Sample purity was confirmed using analytical nuclear magnetic resonance spectroscopy to ensure that trace water or other contaminants did not produce this observation. Raman spectroscopy and simultaneous quartz crystal microbalance/infrared spectroscopy measurements were used to study molecular reorganization during crystallization and decrystallization using trace water in the form of atmospheric moisture. These experimental results were supplemented with density functional theory calculations that indicate imidazolium cation ring stacking and side chain clustering with an exclusive arrangement of the acetate anion in the cation ring plane upon water removal. Crystal structure formation was confirmed using two-dimensional wide-angle X-ray scattering. This natural crystallization is attributed to the removal of trace water over extended periods of time and calls attention to the molecular-level role of water in the structure of hygroscopic ionic liquid systems.

Synthesis of poly(2-isopropyl-2-oxazoline)-b-poly(2-phenyl-2-oxazoline)-b-poly(2-isopropyl-2-oxazoline) and its self-assembly into polymersomes: Temperature-dependent aqueous solution behavior

This study reports on synthesis of poly(2-isopropyl-2-oxazoline)-b-poly(2-phenyl-2-oxazoline)-b-poly(2-isopropyl-2-oxazoline) (PiPOX-b-PPhOX-b-PiPOX) by a three-step sequential monomer addition through cationic ring opening polymerization (CROP). Self-assembly of PiPOX-b-PPhOX-b-PiPOX was triggered through solvent shifting or double emulsion methods, resulting in formation of polymersomes with hydrophilic and temperature-responsive PiPOX inner/outer coronae and hydrophobic PPhOX membrane. Double emulsion method provided smaller polymersomes with greater colloidal stability. Increasing the temperature of the polymersome solution led to formation of polymersome clusters and this transition was found to be irreversible. Glucose oxidase (GOx) encapsulated polymersomes were used as nanoreactors for GOx/horseradish peroxidase (HRP) cascade reactions. The increase in the rate of the enzymatic reaction with increasing temperature was found to be smaller for the encapsulated enzymes compared to free enzymes.

Optimal combination of UV‐induced cationic ring opening polymerization monomers for light‐weight automotive plastic coating

AbstractCROP reactivity of organic coatings composed of three structurally different monomers with epoxy or oxetane derivatives was investigated, focusing on rheological and surface mechanical properties. Real‐time crosslinking behavior of CROP monomers was monitored using a rotational rheometer. Results of differential scanning calorimetry with in situ UV irradiation revealed that the ring opening reactivity of CROP monomers protonated by a photoacid generator (PAG) was correlated with the heat released during the exothermic polymerization reaction. In addition, reaction conversions of monomers with epoxy and oxetane groups were compared using Fourier transform infrared spectroscopy (FT‐IR) under dark curing conditions. Surface and internal mechanical properties of coating films, including adhesion with polycarbonate substrate, were comprehensively evaluated by nano‐indentation, nano‐scratch, and surface and interfacial cutting analysis system (SAICAS) tests. By understanding the unique crosslinking characteristics of each CROP monomer, the ternary CROP monomer system, optimally containing with ECC of 53.6 wt%, DOX of 22.9 wt%, and DEO of 15.3 wt%, exhibited improved crosslinking density (G′ from 104 to 107 Pa) and exceptional mechanical (with scratch resistance increasing from 7.11 to 16.17 mN for Lc1), adhesion (with crosscut resistance increasing from 0 to 5B), and transparency properties, surpassing the performance of unitary ECC coating system.

Syntheses and crystal structures of four 4-(4-meth-oxy-phen-yl)piperazin-1-ium salts: tri-fluoro-acetate, 2,3,4,5,6-penta-fluoro-benzoate, 4-iodo-benzoate, and a polymorph with 4-methyl-benzoate.

Syntheses and X-ray crystal structures of four 4-(4-meth-oxy-phen-yl)piperazin-1-ium (MeOPP) salts, with 2,2,2-tri-fluoro-acetate, C11H17N2O+·C2F3O2 - (I), 2,3,4,5,6-penta-fluoro-benzoate, C11H17N2O+·C7F5O2 -·H2O (II), 4-iodo-benzoate C11H17N2O+·C7H4IO2 -·H2O (III), and 4-methyl-benzoate, C11H17N2O+·C8H7O2 -·H2O (IV) anions are presented. The salts form directly from equimolar qu-anti-ties of N-(4-meth-oxy-phen-yl)piperazine and the corresponding organic acid in methanol and crystallize from 1:1 methanol/ethyl acetate. Salt I is anhydrous whereas II, III, and IV are all monohydrates. In all cases, the MeOPP cation conformation is determined by the torsion about the N-C bond between the piperazinium and 4-meth-oxy-benzene rings. Crystal packing in each structure is largely dictated by N-H⋯O and (in II, III, and IV) O-H⋯O hydrogen bonds, although each also features weak C-H⋯O-type hydrogen bonds. Salt II also has π-π-stacking inter-actions between cation and anion arene rings, and III exhibits I⋯I close contacts.

Construction and Hierarchical Self-Assembly of Multifunctional Coordination Cages with Triangular Metal–Metal-Bonded Units

Herein, a series of face-capped (Tr2M3)4L4 (Tr = cycloheptatrienyl cationic ring; M = metal; L = organosulfur ligand) tetrahedral cages 1-3 functionalized with 12 appended crown ether moieties were designed and synthesized. The reversible binding of ammonium cations with peripheral crown ether moieties to adjust internal guest-binding was realized. Combination of a bisammonium linker and cage 3 led to the formation of a supramolecular gel SPN1 via host-guest interactions between the crown ether moieties and ammonium salts. The obtained supramolecular gel exhibited multiple-stimuli responsiveness, injectability, and excellent self-healing properties and could be further developed to a SPN1-based drug delivery system. In addition, the storage modulus of SPN1 was 20 times higher than that of the model gel without Pd-Pd bonded blocks, and SPN1 had better self-healing properties compared with the latter, demonstrating the importance of such cages in improving mechanical strength without losing the dynamic properties of the material. The cytotoxicity in vitro of the drug-loaded (doxorubicin or methotrexate) SPN1 was significantly improved compared to that of free drugs.

The effect of alkyl chain length on imidazole chloroaluminate ionic liquid/Pt(1 1 1) interface and aluminum deposition: A DFT-D3 study

The structure, active sites, and adsorption mechanism of imidazole-based ionic liquids ([CnMIM]Al2Cl7) (n = 1, 2, 4, or 6) on the Pt(111) surface and their effects on aluminum electrodeposition were evaluated by first-principles approaches. The active sites of imidazolium ILs were on the cationic imidazole ring. The adsorption order was [HMIM]Al2Cl7 >[BMIM]Al2Cl7 >[EMIM]Al2Cl7 > [C1MIM]Al2Cl7. The electrostatic interaction, electrostatic induction, and the interfacial dipole effect made the ionic liquids with longer alkyl chain increase the coverage of cations on the Pt(111) surface as well as the number of charge transfers from ionic liquids to the Pt(111) surface, and decrease the distance between chlorine atoms and the Pt(111) surface. This is beneficial to suppress the dendrite formation during the electrochemical process and deposit aluminum in smaller sizes. These results will provide a basis for the selection of efficient ionic liquids of aluminum electrodeposition.

New organic ionic plastic crystals based on pyrrolidinium dication for a solid‐phase electrolyte

AbstractA series of 1,4‐bis(N‐alkylpyrrolidinium)butane salts combined with Br−, I−, PF6−, and Tf2N− anions were newly designed and synthesized. In nonpolar CDCl3 solution, the axial and equatorial proton peaks of the bis‐pyrrolidinium cation ring are distinguished in 1H NMR. Also, the strengths of ion paring could be estimated from the 1H NMR chemical shift changes of the bridge and pyrrolidinium proton peaks. 1,4‐Bis(N‐hepthylpyrrolidinium)butane I− is an organic ionic plastic crystal showing the lowest fusion entropy value (ΔSf = 3.4 J K·mol−1). Softer crystalline morphologies were found by polarized optical microscope images at plastic crystal phase of each sample and the results were corresponding to differential scanning calorimetry results. 1,4‐Bis(N‐ethylpyrrolidinium)butane Tf2N− showed the softest crystal phase. Ionic conductivity changes and electrochemical stabilities of the bis‐pyrrolidinium PF6− and Tf2N− salts were also measured, and they were stable up to 4.3 V (vs. Li/Li+) and expected to be applied as an electrolyte component.

New organic ionic plastic crystals utilizing the morpholinium cation.

Organic ionic plastic crystals (OIPCs) are emerging candidates as safer, quasi solid-state ion conductors for various applications, especially for next-generation batteries. However, a fundamental understanding of these OIPC materials is required, particularly concerning how the choice of cation and anion can affect the electrolyte properties. Here, we report the synthesis and characterisation of a range of new morpholinium-based OIPCs and demonstrate the benefit of the ether functional group in the cation ring. Specifically, we investigate the 4-ethyl-4-methylmorpholinium [C2mmor]+ and 4-isopropyl-4-methylmorpholinium [C(i3)mmor]+ cations paired with bis(fluorosulfonyl)imide [FSI]- and bis(trifluoromethanesulfonyl)imide [TFSI]- anions. A fundamental study of the thermal behaviour and transport properties was performed using differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and electrochemical impedance spectroscopy (EIS). The free volume within the salts has been investigated by positron annihilation lifetime spectroscopy (PALS) and the ion dynamics using solid-state nuclear magnetic resonance (NMR) analysis. Finally, the electrochemical stability window was studied using cyclic voltammetry (CV). Out of the four morpholinium salts, [C2mmor][FSI] exhibits the widest phase I range from 11 to 129 °C, which is advantageous for their application. [C(i3)mmor][FSI] displayed the highest conductivity of 1 × 10-6 S cm-1 at 30 °C, whereas the largest vacancy volume of 132 Å3 was found for [C2mmor][TFSI]. These insights into the properties of new morpholinium-based OIPCs will be important for developing new electrolytes with optimised thermal and transport properties for a range of clean energy applications.

Rapid access to polycyclic thiopyrylium compounds from unfunctionalized aromatics by thia-APEX reaction.

We developed a sulfur-embedding annulative π-extension (thia-APEX) reaction that could construct a sulfur-embedding cationic hexagonal aromatic ring, thiopyrylium, onto unfunctionalized aromatics in one step. The key of thia-APEX is the use of S-imidated ortho-arenoyl arenethiols, and a variety of π-extended thiopyryliums can easily be synthesized. The synthesized thiopyryliums showed diverse absorption and emission properties over the visible light to NIR region, depending on minor structural differences.

End-functionalized diblock copolymers by mix and match of poly(2-oxazoline) and polyester building blocks

2-(4-(Iodomethyl)benzyl)isoindoline-1,3-dione was utilized as a protected amine-functionalized initiator for the cationic ring opening-polymerization (CROP) of 2-ethyl-2-oxazoline. As kinetic studies indicated a well-controlled polymerization, the CROP was terminated with sodium azide. Subsequent deprotection of the α-end group enabled successive attachment of a targeting ligand, e.g., retinoic acid or a proteogenic amino acid as a peptide model at the α-chain end. The heterotelechelic PEtOx were coupled to cyclooctyne end-functionalized polylactide, which was obtained by initiating the ring opening polymerization of l-lactide via a cyclooctyne based alcohol, utilizing strain-promoted azide-alkyne cycloaddidtion. In-depth characterization via mass spectrometry, 1H NMR spectroscopy, size exclusion chromatography, and infrared spectroscopy investigations verified the success of all synthetic steps and the preservation of retinoyl and leucine moieties also in the end-functionalized PEtOx-b-PLA block copolymers. Circumventing potential degradation of the polyester block during ligand attachment, the heterotelechelic PEtOx represents a universal building block useful for modular approaches towards tailored materials for nanomedicine.

A zwitterionic copolymer as fluid loss reducer for water-based drilling fluids in high temperature and high salinity conditions

With the exploration and development of deep and ultra-deep oil/gas resources, higher challenges have been placed on the performance of water-based drilling fluids (WBDFs). Integrating synergistic characteristics such as excellent high temperature- and salt-resistance, rheology, and fluid loss control capabilities is still a massive challenge for water-based drilling fluid loss reducers. Herein, an innovative temperature- and salt-resistant zwitterionic copolymer filtration reducer was synthesized using N, N-dimethyl acrylamide, 1-(2-carboxyethyl)-3-vinyl imidazolium chloride, sulfobetaine vinyl imidazole through free radical copolymerization. Due to the excellent rigid cationic imidazole ring and salt-resistant hydration groups in the copolymer, the copolymer can be efficiently adsorbed on the surface of bentonite particles through strong electrostatic force and hydrogen bonds, thus maintaining the excellent hydration and dispersibility of bentonite particles. Even after aging at high temperatures (up to 200 °C) and high salinity (saturated salt) conditions, the DCS-based drilling fluids still exhibit excellent rheological and filtration properties (FLAPI < 10 mL), showing the potential for application in deep and ultra-deep drilling operations.

Free and Complexed Fluoropentazoles: Anomalous Ring Charge and Appreciable Kinetic Stability.

Fluoronitrogens are strongly related to high-energy density materials. Fluoropentazole (cyclo-FN5) with hitherto the highest N/F ratio at ambient pressure belongs to the family of well-known and 119-year-old pentazoles. Due to the presence of the overwhelmingly electronegative F element, cyclo-FN5 is the only pentazole to date that contains a cationic N5 ring. However, also due to F's large electronegativity, the reported ring-destruction barrier of cyclo-FN5 is nearly the lowest (6.7 kcal/mol), which has made its synthesis and characterization quite difficult. Here, cyclo-FN5 was re-predicted to bear an almost doubled ring-destruction barrier (∼12-14 kcal/mol) at the CBS-QB3, G4, W1BD, CCSD(T)/CBS//CCSD/cc-pVTZ, and CCSD(T)/CBS//CCSD(T)/aug-cc-pVTZ levels. Promisingly, upon further complexation with Lewis acid(s), the ring-destruction barrier of cyclo-FN5 might reach 23 kcal/mol, which is comparable to that of the well-known and already synthesized arylpentazoles (∼20 kcal/mol), and the positive charge on the N5 ring can be increased to 0.66 |e|.

Ordered mesoporous silica matrices supported ionic liquids for efficient CO2 separation from CO2/CH4 gas mixture: Experimental and theoretical investigation

Global concern over CO2 reduction to avoid global warming has escalated due to alarming CO2 concentrations in the atmosphere. In this connection, supported-ionic liquids (SILs) have been prepared by physically imbibition of 1-ethyl-3-methylimidazolium tetrafluoroborate (C2mim BF4) ionic liquid (IL) into ordered mesoporous silica (MS) matrices to design SILs-membranes (SILMs) for gas separation technology. These SILs were characterized by powder XRD, 29Si NMR, SEM, FTIR, and 1H NMR spectroscopy, N2 sorption, and TGA analyses. FTIR study reveals that vibrational frequencies related to C2mim+ cation ring remain unchanged upon confinement of nanopores of MS whereas Si-O-Si band, Si-O band, and anion band shifted indicating IL interacting with the MS surfaces. Density functional theory (DFT) calculations also explore the structural features of these SILs. SILMs based on Pebax-1657 were also designed using a solution casting technique to evaluate their gas separation performance and characterized using XRD and SEM techniques. C2mimBF4/MCM-48 membrane exhibit higher permeability for CO2 both in single and mixed gas studies. These results were further supported by DFT analysis in terms of complexation energies (Ec) which demonstrates the strong affinity of these SILs membranes towards CO2 and CH4 gases, respectively. Further, a nice correlation was established between the experimental and theoretical findings.

Poly(2-oxazoline) - Ferrostatin-1 drug conjugates inhibit ferroptotic cell death.

Ferroptosis is a form of non-apoptotic iron induced cell death mechanism implicated in neurodegeneration, yet can be ameliorated with potent radical scavengers such as ferrostatin-1 (Fer-1). Currently, Fer-1 suffers from low water solubility, poor biodistribution profile and is unsuitable for clinical application. Fer-1 polymer-drug conjugates (PDCs) for testing as an anti-ferroptosis therapeutic candidate have yet to be described. Here, we report the synthesis and characterization of a library of water-soluble Fer-1 based poly(2-oxazoline)-drug conjugates. The cationic ring opening polymerization (CROP) of water-soluble 2-oxazoline monomers, and a novel protected aromatic aldehyde 2-oxazoline (DPhOx), produced defined copolymers, which after deprotection were available for modification with Fer-1 via reductive amination and Schiff base chemistry. The conjugates were tested for their activity against RSL3-induced ferroptosis in vitro, and first structure-activity relationships were established. Irreversibly conjugated Fer-1 PDCs possessing an arylamine structural motif showed a greatly increased anti-ferroptosis activity compared to reversibly (Schiff base) linked Fer-1. Overall, this work introduces the first active ferrostatin-PDCs and a new highly tuneable poly(2-oxazoline)-based PDC platform, which provides access to next generation polymeric nanomaterials for anti-ferroptosis applications.

The structures of eleven (4-phen-yl)piperazinium salts containing organic anions.

Eleven (4-phen-yl)piperazinium salts containing organic anions have been prepared and structurally characterized, namely, 4-phenyl-piperazin-1-ium 4-fluoro-benzoate monohydrate, C10H15N2 +·C7H4FO2 -·H2O, 1; 4-phenyl-piperazin-1-ium 4-bromo-benzoate monohydrate, C10H15N2 +·C7H4BrO2 -·H2O, 3; 4-phenyl-piperazin-1-ium 4-iodo-benzoate, C10H15N2 +·C7H4IO2 -, 4; 4-phenyl-piperazin-1-ium 4-nitro-benzoate, C10H15N2 +·C7H4NO4 -, 5; 4-phenyl-piperazin-1-ium 3,5-di-nitro-salicylate, C10H15N2 +·C7H3N2O7 -, 6; 4-phenyl-piperazin-1-ium 3,5-di-nitro-benzoate, C10H15N2 +·C7H3N2O6 -, 7; 4-phenyl-piperazin-1-ium picrate, C10H15N2 +·C6H2N3O7 -, 8; 4-phenyl-piperazin-1-ium benzoate monohydrate, C10H15N2 +·C7H5O2 -·H2O, 9; 4-phenyl-piperazin-1-ium p-toluene-sulfonate, C10H15N2 +·C7H7O3S-, 10; 4-phenyl-piperazin-1-ium tartarate monohydrate, C10H15N2 +·C4H5O6 -·H2O, 11; and 4-phenyl-piperazin-1-ium fumarate, C10H15N2 +·C4H3O4 -, 12. Compounds 1 and 3-12 are all 1:1 salts with the acid proton transferred to the phenyl-piperaizine basic N atom (the secondary amine) with the exception of 3 where there is disorder in the proton position with it being 68% attached to the base and 32% attached to the acid. Of the structures with similar stoichiometries only 3 and 9 are isomorphous. The 4-phenyl substituent in all cases occupies an equatorial position except for 12 where it is in an axial position. The crystal chosen for structure 7 was refined as a non-merohedral twin. There is disorder in 5, 6, 10 and 11. For both 5 and 6, a nitro group is disordered and was modeled with two equivalent orientations with occupancies of 0.62 (3)/0.38 (3) and 0.690 (11)/0.310 (11), respectively. For 6, 10 and 11, this disorder is associated with the phenyl ring of the phenyl-piperazinium cation with occupancies of 0.687 (10)/0.313 (10), 0.51 (7)/0.49 (7) and 0.611 (13)/389 (13), respectively. For all salts, the packing is dominated by the N-H⋯O hydrogen bonds formed by the cation and anion. In addition, several structures contain C-H⋯π (1, 3, 4, 8, 9, 10, and 12) and aromatic π-π stacking inter-actions (6 and 8) and one structure (5) contains a -NO2⋯π inter-action. For all structures, the Hirshfeld surface fingerprint plots show the expected prominent spikes as a result of the N-H⋯O and O-H⋯O hydrogen bonds.

Identification of a novel multifunctional oxidosqualene cyclase from Zea mays sheds light on the biosynthetic pathway of three pentacyclic triterpenoids

Zea mays (maize) is an important agricultural crop that produces a variety of valuable terpenoids, including several triterpenoids. However, no oxidosqualene cyclase (OSC) enzymes, which catalyze the first step in triterpenoid biosynthesis, have been identified in maize. Here, we identified a novel OSC (ZmOSC1) in maize using a combination of genomic mining and phylogenetic analyses. To functionally characterize the candidate OSC, we constructed a yeast strain that produced high levels of 2,3-oxidosqualene. When ZmOSC1 was expressed in this strain, three compounds were detected and identified as hop-17(21)-en-3-ol, hopenol B and simiarenol, respectively. For their biosynthesis, we proposed a potential cyclization mechanism catalyzed by ZmOSC1 via the generation of a dammarenyl cation, followed by sequential cationic ring expansion, cyclization, cationic migration and further proton elimination. This study discovered and characterized an OSC from maize for the first time, and laid a foundation to produce three bioactive pentacyclic triterpenes, hop-17(21)-en-3-ol, hopenol B and simiarenol, using synthetic biology approaches.

Bottom-up synthesis of cationic porphyrin-based porous organic polymers for highly efficient and selective recovery of gold

Developing ionic porous organic polymers (i-POPs) to retrieve gold from electronic waste is still in its infancy. Herein, for the first time, a cationic imidazolium and porphyrin cross-linked POPs, Imi-PPOPs-Br, was constructed by combining pyrrole and imidazolium-functionalized trialdehydes via the bottom-up method. As expected, the introduction of cationic imidazolium and porphyrin rings has endowed material high adsorption capacity (1543 mg/g), preferable reusability (more than eight times), and specific selectivity to Au (III). Multiple characterization results and density functional theory (DFT) calculations revealed that the adsorption mechanism of Au (III) by Imi-PPOPs-Br could be due to the electrostatic interaction between cationic Imi-PPOPs-Br and AuCl4− anions, strong bind of Au and N active sites, and reductive immobilization of Au (III) to Au (0). This study may put forward a new and facile strategy for constructing stable i-POPs that can be used as desirable absorbents in environmental fields.

Development of in situ polymerized amines into mesoporous silica for direct air CO2 capture

Direct air CO2 capture (DAC) is inevitable to achieve negative emissions and lower CO2 concentration in the atmosphere. The use of class III supported amine materials has shown great potential as effective materials for CO2 capture from both flue gas and low concentrations of CO2. In this work, a linear polyethylene amine tethered to mesoporous silica foam was synthesized by controlled in situ cationic ring opening polymerization of 2-methyl-2-oxazoline. The sorbent was characterized based on porosity, FTIR, elemental analysis, and surface morphology. The CO2 capture performance at different temperatures was measured using a volumetric method, whereas the dynamic breakthrough analysis (DBA) technique was evaluated using simulated air of 400 ppm CO2 at different temperatures and relative humidities. The CO2 adsorption isotherms were studied in the temperature range from 5 to 80 °C and were fitted using different isotherm models. To evaluate the effects of moisture on the CO2 capture performance, breakthrough experiments were performed using 400 ppm CO2 at various relative humidities (0–65%). It was found that the CO2 uptake calculated from the breakthrough experiment is enhanced at higher moisture contents and decreases at higher temperatures. The maximum CO2 uptake was 1.50 mmol/g at 25 °C and 65% RH. The CO2 adsorption kinetics of the sorbent was found to follow the Avrami model, whereas the dual site Langmuir model was found to be the best fit for the adsorption isotherms. The developed sorbent exhibited a stable cyclic performance and retained its initial CO2 uptake during 10 consecutive cycles. This study demonstrates that in situ polymerization of amines into porous supports is a viable route for designing sorbents with high CO2 adsorption performance for DAC applications.

Cooperative catalysis: Condensation-aromatization for synthesis of 2-(4-nitrophenyl)-1H-benzimidazole by silica immobilized Brønsted-Lewis acidic ionic liquid (Si-BLAIL)

Herein, pleasing the advantageous of both Brønsted and Lewis acidic site of Si-BLAIL the condensation-aromatization reaction has been carried out. The striking distinctiveness of work is optimum reaction condition, easy work-up, high yield, catalyst recyclability, non-inertness of reaction flask, simple catalyst loading method. The decreases in the amount of catalyst and reaction time shows good to high (71%–93%) yield suggests about the involvement of some interesting mechanism such as cooperative catalysis. The mechanism has been hypothesizes as, the Si-BLAIL increase the efficiency of condensation reaction possibly by providing the proton in 2-position of cationic imidazolium ring of BLAIL through the hydrogen bond interaction with carbonyl group and nucleophilic activation during aromatization by hydrogen bond acceptor ability of Lewis adduct anion of BLAIL. The catalyst Si-BLAIL shows massive affirm for industrial applications. The Si-BLAIL has identified as the best acid catalyst for 2-(4-nitrophenyl) benzimidazole synthesis with additional benefits of cooperative catalysis.