Imidazolium-based Ionic Polymer Research Articles

Incorporation of phenolic skeleton into imidazolium ionic polymers as recyclable catalysts for efficient fixation of CO2 into cyclic carbonates

Developing a greener and efficient catalysts towards the direct fixation of atmospheric CO2 and then being used to synthesize high-value chemicals is of great interest, but challenging. To achieve this aim, rational design of the catalyst is very important. Herein, three imidazolium-based ionic polymers (IPs), named as IP 1–IP 3, are straightforwardly synthesized through a simple one-pot quaternization method by employing benzyl chloride linkers and tri-imidazole monomers (L1 and L2). These IPs are fully characterized using FTIR spectroscopy, 13C MAS NMR, XRD, elemental analysis, SEM with elemental mapping, HRTEM, TGA, XPS spectroscopy, nitrogen adsorption–desorption, and CO2/NH3-TPD methods. The newly synthesized IP 1 catalyst with phenolic hydroxyl shows an excellent catalytic activity toward CO2 cycloaddition with 97.1 % yield of cyclic carbonate under mild conditions (80 °C, 0.1 MPa CO2, solvent-free, 4.5 h). Moreover, the IP 1 catalyst is highly robust and can be reused at least for 7 consecutive runs. Mechanistic studies indicate that the synergic effect of hydrogen bonding and halogen anion in the IP 1 catalyst afford the ability to activate the substrate and ease the reaction kinetics, which results in an enhanced catalytic efficiency toward CO2 fixation. This work provides an efficient new method for the design and synthesis of multifunctional heterogeneous catalysts for the CO2 cycloaddition reaction.

Activity-based molecular CO2 detection by amine-free polymers in organic and aqueous media

Many machineries have been developed to detect and monitor the ubiquitous molecule “CO2” in a global warming essay. CO2 detection in water with amine-free functionalities and N-heterocyclic carbene (NHC)-based systems remains of interest in the sensing community. This manuscript introduces a unique fluorescent polymeric system capable of CO2 detection in organic and water media. The imidazolium-based ionic polymer controls fluorescence using an ON/OFF mechanism. The formation of the complex NHC-CO2- turns “ON” fluorescence in organic media and solid films through the photo-induced transmission “OFF” photophysical phenomenon. In contrast, fluorescence quenching was observed in the water medium due to aggregation-caused quenching (ACQ) of polymeric nanoparticles upon CO2 gas introduction, which resulted in the formation of carbamate anions in water. The single ionic polymer P1 works in a multimode pathway and detects CO2 gas in various phases such as organic solvents, water, and solid films, through fluorometric analysis.

Building internal electric fields in porous ionic polymers for fast photocatalytic degradation of tetracycline hydrochloride

Porous imidazolium-based ionic polymers are obtained for photodegradation of target antibiotics of tetracycline hydrochloride (TCH) by constructing the IEF through regulating the valence state of photosensitive groups.

Facile Construction of Carboxyl-Functionalized Ionic Polymer towards Synergistic Catalytic Cycloaddition of Carbon Dioxide into Cyclic Carbonates

The development of bifunctional ionic polymers as heterogeneous catalysts for effective, cocatalyst- and metal-free cycloaddition of carbon dioxide into cyclic carbonates has attracted increasing attention. However, facile fabrication of such polymers having high numbers of ionic active sites, suitable types of hydrogen bond donors (HBDs), and controlled spatial positions of dual active sites remains a challenging task. Herein, imidazolium-based ionic polymers with hydroxyl/carboxyl groups and high ionic density were facilely prepared by a one-pot quaternization reaction. Catalytic evaluation demonstrated that the presence of HBDs (hydroxyl or carboxyl) could enhance the catalytic activities of ionic polymers significantly toward the CO2 cycloaddition reaction. Among the prepared catalysts, carboxyl-functionalized ionic polymer (PIMBr-COOH) displayed the highest catalytic activity (94% yield) in the benchmark cycloaddition reaction of CO2 and epichlorohydrin, which was higher than hydroxyl-functionalized ionic polymer (PIMBr-OH, 76% yield), and far exceeded ionic polymer without HBDs groups (PIMBr, 54% yield). Furthermore, PIMBr-COOH demonstrated good recyclability and wide substrate tolerance. Under ambient CO2 pressure, a number of epoxides were smoothly cycloadded into cyclic carbonates. Additionally, density functional theory (DFT) calculation verified the formation of strong hydrogen bonds between epoxide and the HBDs of ionic polymers. Furthermore, a possible mechanism was proposed based on the synergistic effect between carboxyl and Br− functionalities. Thus, a facile, one-pot synthetic strategy for the construction of bifunctional ionic polymers was developed for CO2 fixation.

Quaternary amine synthesized ionic polymer for efficient removal of Cr(VI) in waste water

A series of imidazolium-based ionic polymer (ImIP2Br, ImIP3Br and ImIP4Br) were successfully prepared by quaternization reaction of 1,4-dimethyl bromide benzene, 1,3,5-tri(bromomethyl), 1,2,4,5-tetramethyl and 1,3,5-tri(1H-imidazol-1-yl)benzene. The as-prepared ImIP2Br, ImIP3Br and ImIP4Br ionic polymers were characterized by SEM, STEM, FTIR, TG and solid-state 13C NMR measurement. In the aqueous solution of [imidazolium] to [Cr] 1:1, the removal rate of Cr(VI) by ImIP4Br was 98.4%, which was much higher than that of ImIP2Br, ImIP3Br. In addition, the ImIP4Br was applied for efficient removal of Cr(VI) for extremely low concentration of Cr(VI) solution and electroplating industry wastewater by anion exchange. Finally, a series of experimentals studies were performed to study the enrichment of hexavalent chromium and evaluate the recycling and reproducibility of ImIP4Br. The result showed the concentration of the residual Cr(VI) is only 0.09 mg L−1, which is lower than the permissible limit of Cr(VI) discharge (0.10 mg L−1) according to the regulations of the US Environmental Protection Agency. For the actual electroplating wastewater, the adsorption efficiency of ImIP4Br for Cr(VI) is over 99.8%, despite the competitive adsorption of other ions in the solution. In a word, ImIP4Br shows outstanding enrichment ability, good regenerative ability and superior recyclability for removal of Cr(VI). The combination of promising removal performances endows ImIP4Br with great promises for capture and separation of Cr(VI) from contaminated water systems.

Carbon Dioxide Conversion Upgraded by Host‐guest Cooperation between Nitrogen‐Rich Covalent Organic Framework and Imidazolium‐Based Ionic Polymer

Invited for this month's cover are the groups of Rongjian Sa and Ruihu Wang at Minjiang University and the Chinese Academy of Sciences. The image shows how host-guest composite catalysts with task-specific components for the cycloaddition of CO2 with epoxides have been developed through integrating nitrogen-rich covalent organic framework and imidazolium-based ionic polymer. The Full Paper itself is available at 10.1002/cssc.202006158.

Carbon Dioxide Conversion Upgraded by Host-guest Cooperation between Nitrogen-Rich Covalent Organic Framework and Imidazolium-Based Ionic Polymer.

The chemical conversion of CO2 into value-added chemicals is one promising approach for CO2 utilization. It is crucial to explore highly efficient catalysts containing task-specific components for CO2 fixation. Here, a host-guest catalytic system was developed by integrating nitrogen-rich covalent organic framework (TT-COF) and imidazolium-based ionic polymer (ImIP), which serve as hydrogen-bonding donor and nucleophilic agent, respectively, for cooperatively facilitating the activation of the epoxides and subsequent CO2 cycloaddition. The catalytic activity of the host-guest system was remarkably superior to those of ImIP, TT-COF, and their physical mixture. Furthermore, selective adsorption for CO2 over N2 rendered this catalytic system effective for the cycloaddition reaction of the simulated flue gas. The protocols for the unification of two catalytically active components provide new opportunities for the development of composite systems in multiple applications.

Robust ruthenium diphosphide nanoparticles for pH-universal hydrogen evolution reaction with platinum-like activity

Development of cost-effective and durable electrocatalysts with Pt-like activity for pH-universal hydrogen evolution reaction (HER) is highly desirable but challenging. Herein, we report a new methodology for facile fabrication of robust electrocatalysts consisting of N, P-codoped carbon (NPC)-encapsulated RuP2 nanoparticles around carbon nanotubes (CNTs), which shows unprecedented HER activity and high durability in all-pH range. The method involves the conformal coating of the imidazolium-based ionic polymer (ImIP) on CNTs surface, anion metathesis and subsequent phosphorization, the multistep synthetic protocol allows for deliberate modulation of the electrocatalysts. ImIP effectively inhibits the aggregation of RuP2 during phosphorization to form small-sized RuP2 nanoparticles, while NPC significantly increases the conductivity, intrinsic activity and stability of RuP2. The remarkably low overpotentials of 12, 15 and 13 mV are required to achieve a current density of 10 mA cm−2 in 1.0 M KOH, 1.0 M PBS and 0.5 M H2SO4, respectively. This work provides a feasible method to develop new type of Pt-like electrocatalysts for HER in all-pH range.

Incorporation of flexible ionic polymers into a Lewis acid-functionalized mesoporous silica for cooperative conversion of CO2 to cyclic carbonates

AbstractA rational integration of multiple reactive centers into a combined unit to facilitate their cooperative effects is a smart approach for accelerating the catalytic activity. Here, to achieve this goal, linear imidazolium-based ionic polymers were confined into the nanopores of mesoporous silica nanospheres anchored with homogeneously distributed zinc salts. Owing to the flexible character and the reinforced cooperative effects of the ionic liquid (nucleophile) and zinc species (Lewis acid) in the confined mesoporous structure, the resultant composite exhibited dramatically improved catalytic performance in the cycloaddition of CO2 with epoxides to form cyclic carbonates. This was in contrast to that observed for the individual catalytic components. Moreover, such a solid catalyst could be easily recovered and reused four times without a significant loss of activity.

Platinum nanoparticles confined in imidazolium-based ionic polymer for assembling a microfluidic reactor with enhanced catalytic activity

A synthetic strategy is developed to grow Pt nanoparticles supported by imidazolium-based ionic polymers (Pt/ImIP-2BrB) on the inner surface of fused-silica capillary. The imidazolium-based ionic polymers ImIP-2BrB are prepared from condensation of tetrakis[4-(1-imidazolyl)phenyl]methane and 1,4-bis-bromomethyl-benzene and are employed to support Pt nanoparticles. The capillary coated with Pt/ImIP-2BrB is further assembled to achieve a catalytic microfluidic reactor. The catalytic activity is probed in either the reduction of nitrobenzene derivatives or the hydrosilylation of phenylacetylene with triethylsilane by flowing through the microfluidic reactor. The catalytic microfluidic reactor demonstrates significantly enhanced activity about 2–8 times in comparison with the corresponding reactions under batch conditions. The reactor greatly reduces the amount of Pt upon achieving similar yields. It also shows good recyclability without significant decrease of the activity.

Engineered Interfusion of Hollow Nitrogen‐Doped Carbon Nanospheres for Improving Electrochemical Behavior and Energy Density of Lithium–Sulfur Batteries

AbstractHollow nanostructures are one of promising sulfur host materials for lithium–sulfur (Li–S) batteries, but the ineffective contact among discrete particles usually generates overall poor electrical conductivity and low volumetric energy density. A new interfused hollow nitrogen‐doped carbon (HNPC) material, derived from imidazolium‐based ionic polymer (ImIP)‐encapsulated zeolitic imidazolate framework‐8 (ZIF‐8), is reported. A novel method for ZIF‐8 disassembly induced by the decomposition of the ImIP shell is proposed. The unique structural superiority gives the resultant electrodes remarkable cycling stability, high rate capability, and large volumetric energy density. A stable reversible discharge capacity over 562 mA h g−1 at 2 C is achieved after prolonged cycling for 800 cycles and the average capacity decay per cycle is as low as 0.035%. The electrochemical performance achieved greatly surpasses that of ZIF‐8‐derived carbon matrices and conventional nitrogen‐doped carbon materials. This proposed methodology opens a new avenue for the design of hollow‐structured carbon nanoarchitectures with target functionalities.

Dyadic promotion of photocatalytic aerobic oxidation via the Mott–Schottky effect enabled by nitrogen-doped carbon from imidazolium-based ionic polymers

Metal/semiconductor heterojunction systems have demonstrated outstanding photocatalytic performance owing to the Mott–Schottky effect enabled by nitrogen-doped carbon.

Urea-Functionalized Imidazolium-Based Ionic Polymer for Chemical Conversion of CO2 into Organic Carbonates

Conversion of carbon dioxide (CO2) into useful chemicals is one of promising approaches to reduce global warming and the energy crisis. It is pivotal to develop heterogeneous catalytic systems cont...

Water-Soluble and Low-Toxic Ionic Polymer Dots as Invisible Security Ink for MultiStage Information Encryption.

Nanodots are attractive stimuli-responsive luminescence materials for anti-counterfeiting and information encryption. However, their applications are limited by low water solubility and single-mode information identification by naked eyes under UV light illumination. Herein, we report one type of new nanodots, main-chain imidazolium-based ionic polymer dots (IPDs). There is no edge effect in IPDs, and the ionic groups are homogenously distributed in the entire dot. IPDs exhibit high water solubility, good stability, narrow size distribution, low toxicity, and exceptional optical performance without additional modification. Written information using aqueous IPD solution is invisible in natural light, but can be recognized by a portable UV lamp. Moreover, they can be further encrypted and decrypted using easily available and nontoxic sodium carbonate and acetic acid, respectively. The encrypted information is invisible in natural light and/or UV light. This study provides a new prospect for high-level data recording and security protection by using water-soluble IPDs as invisible security ink.

Additive-Free Hydrogen Generation from Formic Acid Boosted by Amine-Functionalized Imidazolium-Based Ionic Polymers

Catalytic dehydrogenation of formic acid (FA) is an efficient approach to store and release hydrogen in fuel-cell-based hydrogen economy; it is still a daunting challenge to the design and synthesis of the additive-free heterogeneous catalytic systems. In this contribution, we present an amine-functionalized main-chain imidazolium-based ionic polymer (ImIP-1) for boosting additive-free hydrogen generation from FA. The ultrafine palladium nanoparticles (NPs) with uniform dispersion over ImIP-1 were readily obtained through simple anion exchange between chloride in ImIP-1 and tetrachloropalladate and subsequent reduction with NaBH4. The palladium NPs are synergetically stabilized by coordination interaction and electrostatic effect from ImIP-1. The amine groups in the host backbone of ImIP-1 serve as basic sites to accelerate the cleavage of O–H bond in FA. The catalytic system shows outstanding catalytic activity, high stability, and excellent recyclability in additive-free heterogeneous FA dehydrogenation...

Electrostatic trapping of polysulfides enabled by imidazolium-based ionic polymers for high-energy-density lithium–sulfur batteries

A new lithium polysulfide (PS) trapping strategy based on electrostatic attraction between imidazolium groups and PSs has been demonstrated. Simple introduction of main-chain imidazolium-based ionic polymers into sulfur cathodes results in effective suppression of the PS shuttle effect, thus significantly improving cycling stability of lithium–sulfur batteries.

Facile fabrication of Cu-based alloy nanoparticles encapsulated within hollow octahedral N-doped porous carbon for selective oxidation of hydrocarbons.

Hollow carbon materials with versatile chemical compositions and complicated shell architectures hold great promise in heterogeneous catalysis. However, it is a daunting challenge to synthesize metal alloy nanoparticles (NPs) supported by hollow nanostructures. Herein, we present a simple approach for facile fabrication of Pd-Cu alloy NPs embedded in hollow octahedral N-doped porous carbon (Pd-Cu@HO-NPC). The hollow material is derived from HKUST-1 coated by an imidazolium-based ionic polymer (ImIP). Water-sensitive HKUST-1 is simultaneously removed in the process of anion exchange between bromide in the ImIP shell and tetrachloropalladate in aqueous medium. The released Cu(ii) ions and exchanged Pd(ii) ions serve as Cu and Pd sources in the subsequent pyrolysis. The resultant Pd-Cu@HO-NPC exhibits high catalytic activity, selectivity, stability and recyclability in the aerobic oxidation of hydrocarbons. More attractively, the synthetic strategy is of excellent generality, and could be extended to the synthesis of Cu-based bimetallic and trimetallic alloy NPs, such as Pt-Cu@HO-NPC and Pd-Pt-Cu@HO-NPC. This work highlights the superiority of water-sensitive metal-organic frameworks in the ingenious design of hollow carbon materials incorporated with well-dispersed metal alloy NPs.

Lithium–Sulfur Batteries: The Fusion of Imidazolium‐Based Ionic Polymer and Carbon Nanotubes: One Type of New Heteroatom‐Doped Carbon Precursors for High‐Performance Lithium–Sulfur Batteries (Adv. Funct. Mater. 44/2017)

A heteroatom-doped carbon material for high-performance lithium–sulfur batteries is reported in article number 1703936 by Xiaoju Li, Ruihu Wang, and co-workers. The integration of main-chain imidazolium-based ionic polymer and carbon nanotubes (CNTs) yields porous materials. They can serve as an effective sulfur host, and both the electrical conductivity from CNTs and polysulfide entrapping ability from the heteroatom-doped carbons are inherited and strengthened.

The Fusion of Imidazolium‐Based Ionic Polymer and Carbon Nanotubes: One Type of New Heteroatom‐Doped Carbon Precursors for High‐Performance Lithium–Sulfur Batteries

AbstractRational design of sulfur host materials with high electrical conductivity and strong polysulfides (PS) confinement is indispensable for high‐performance lithium–sulfur (Li–S) batteries. This study presents one type of new polymer material based on main‐chain imidazolium‐based ionic polymer (ImIP) and carbon nanotubes (CNTs); the polymer composites can serve as a precursor of CNT/NPC‐300, in which close coverage and seamless junction of CNTs by N‐doped porous carbon (NPC) form a 3D conductive network. CNT/NPC‐300 inherits and strengthens the advantages of both high electrical conductivity from CNTs and strong PS entrapping ability from NPC. Benefiting from the improved attributes, the CNT/NPC‐300‐57S electrode shows much higher reversible capacity, rate capability, and cycling stability than NPC‐57S and CNTs‐56S. The initial discharge capacity of 1065 mA h g−1 is achieved at 0.5 C with the capacity retention of 817 mA h g−1 over 300 cycles. Importantly, when counter bromide anion in the composite of CNTs and ImIP is metathesized to bis(trifluoromethane sulfonimide), heteroatom sulfur is cooperatively incorporated into the carbon hosts, and the surface area is increased with the promotion of micropore formation, thus further improving electrochemical performance. This provides a new method for optimizing porous properties and dopant components of the cathode materials in Li–S batteries.

Palladium Nanoparticles Stabilized by an Ionic Polymer and Ionic Liquid: A Versatile System for C−C Cross-Coupling Reactions

Highly stable palladium nanoparticles (Pd NPs), protected by an imidazolium-based ionic polymer (IP) in a functionalized ionic liquid (IL), have been prepared and characterized by transmission electron microscopy (TEM). These Pd NPs are excellent precatalysts for Suzuki, Heck, and Stille coupling reactions and can be stored without undergoing degradation for at least 2 years. The NP-IP-IL system may therefore be considered as an alternative to the traditional palladium on carbon (Pd/C) precatalyst employed in many C-C coupling reactions, also allowing reactions to be conducted under "solvent-free" conditions.