Hydrophobic Mesoporous Poly(ionic liquid)s towards Highly Efficient and Contamination-Resistant Solid-Base Catalysts

Pd Clusters on Schiff Base–Imidazole-Functionalized MOFs for Highly Efficient Catalytic Suzuki Coupling Reactions

Subnanometer noble metal clusters have attracted much attention because of abundant low-coordinated metal atoms that perform excellent catalytic activity in various catalytic processes. However, the surface free energy of metals increases significantly with decreasing size of the metal clusters, which accelerates the aggregation of small clusters. In this work, new Schiff base–imidazole-functionalized MOFs were successfully synthesized via the postsynthetic modification method. Highly dispersed Pd clusters with an average size of 1.5 nm were constructed on this functional MOFs and behaved excellent catalytic activity in the Suzuki coupling of phenyboronic acid and bromobenzene (yield of biaryl >99%) under mild reaction conditions. Moreover, the catalyst can be reused six times without loss of activity. Such catalytic behavior is found to closely related to the surface functional groups that promote the formation of small Pd⁰ clusters in the metallic state.

Heterogeneous Catalysis with the Participation of Ionic Liquids

This mini-review briefly describes the recent progress in the design and development of catalysts based on the presence of ionic liquids. In particular, the focus was on heterogeneous systems (supported ionic liquid (IL) phase catalysts (SILPC), solid catalysts with ILs (SCILL), porous liquids), which due to the low amounts of ionic liquids needed for their production, eliminate basic problems observed in the case of the employment of ionic liquids in homogeneous systems, such as high price, high viscosity, and efficient isolation from post-reaction mixtures.

Hydrazine-Enabled One-Step Synthesis of Metal Nanoparticle-Functionalized Gradient Porous Poly(ionic liquid) Membranes

In this communication, a one-step synthetic route is reported toward free-standing metal-nanoparticle-functionalized gradient porous polyelectrolyte membranes (PPMs). The membranes are produced by soaking a glass-plate-supported blend film that consists of a hydrophobic poly(ionic liquid) (PIL), poly(acrylic acid), and a metal salt, into an aqueous hydrazine solution. Upon diffusion of water and hydrazine molecules into the blend film, a phase separation process of the hydrophobic PIL and an ionic crosslinking reaction via interpolyelectrolyte complexation occur side by side to form the PPM. Simultaneously, due to the reductive nature of hydrazine, the metal salt inside the polymer blend film is reduced in situ by hydrazine into metal nanoparticles that anchor onto the PPM. The as-obtained hybrid porous membrane is proven functional in the catalytic reduction of p-nitrophenol. This one-step method to grow metal nanoparticles and gradient porous membranes can simplify future fabrication processes of multifunctional PPMs.

Phosphonium-Based Porous Ionic Polymer with Hydroxyl Groups: A Bifunctional and Robust Catalyst for Cycloaddition of CO2 into Cyclic Carbonates

The integration of synergic hydrogen bond donors and nucleophilic anions that facilitates the ring-opening of epoxide is an effective way to develop an active catalyst for the cycloaddition of CO₂ with epoxides. In this work, a new heterogeneous catalyst for the cycloaddition of epoxides and CO₂ into cyclic carbonates based on dual hydroxyls-functionalized polymeric phosphonium bromide (PQPBr-2OH) was presented. Physicochemical characterizations suggested that PQPBr-2OH possessed large surface area, hierarchical pore structure, functional hydroxyl groups, and high density of active sites. Consequently, it behaved as an efficient, recyclable, and metal-free catalyst for the additive and solvent free cycloaddition of epoxides with CO₂. Comparing the activity of PQPBr-2OH with that of the reference catalysts based on mono and non-hydroxyl functionalized polymeric phosphonium bromides suggested that hydroxyl functionalities in PQPBr-2OH showed a critical promotion effect on its catalytic activity for CO₂ conversion. Moreover, PQPBr-2OH proved to be quite robust and recyclable. It could be reused at least ten times with only a slight decrease of its initial activity.

Porous Polyelectrolytes: The Interplay of Charge and Pores for New Functionalities

The past decade has witnessed rapid advances in porous polyelectrolytes and there is tremendous interest in their synthesis as well as their applications in environmental, energy, biomedicine, and catalysis technologies. Research on porous polyelectrolytes is motivated by the flexible choice of functional organic groups and processing technologies as well as the synergy of the charge and pores spanning length scales from individual polyelectrolyte backbones to their nano-/micro-superstructures. This Review surveys recent progress in porous polyelectrolytes including membranes, particles, scaffolds, and high surface area powders/resins as well as their derivatives. The focus is the interplay between surface chemistry, Columbic interaction, and pore confinement that defines new chemistry and physics in such materials for applications in energy conversion, molecular separation, water purification, sensing/actuation, catalysis, tissue engineering, and nanomedicine.

Studies on the uptake of Am(III) and Eu(III) on ionic liquid modified polystyrene-divinyl benzene

Imidazolium bis(2-ethylhexyl)phosphate ionic liquid was anchored on a polystyrene-divinylbenzene (PS-DVB) copolymer and the product (R-Im-DEHP) was studied for the extraction of Am(III) and Eu(III) from dilute nitric acid medium to examine the feasibility using the anchored adsorbent for their mutual separation. The effect of various parameters such as the duration of equilibration, concentration of nitric acid, europium ion, and diethylenetriaminepentaacetic acid (DTPA) in aqueous phase on the distribution coefficient (K d) of Am(III) and Eu(III) was studied. The distribution coefficient of Am(III) and Eu(III) decreased with increase in the concentration of nitric acid. Rapid extraction of metal ions in the initial stages of equilibration followed by the establishment of equilibrium occurred within 4 h. The data on the rate of uptake of Am(III) and Eu(III) were fitted into pseudo-first order and pseudo-second order rate equation. The extraction isotherm was fitted to Langmuir and Freundlich adsorption models and the apparent europium extraction capacity was determined. The mechanism of extraction was elucidated and the conditions needed for efficient separation of Am(III) from Eu(III) was optimized using DTPA. The study indicated the possibility of using R-Im-DEHP for the separation of Eu(III) from Am(III) with high separation factors.

Advances in Organic and Organic-Inorganic Hybrid Polymeric Supports for Catalytic Applications

In this review, the most recent advances (2014-2016) on the synthesis of new polymer-supported catalysts are reported, focusing the attention on the synthetic strategies developed for their preparation. The polymer-supported catalysts examined will be organic-based polymers and organic-inorganic hybrids and will include, among others, polystyrenes, poly-ionic liquids, chiral ionic polymers, dendrimers, carbon nanotubes, as well as silica and halloysite-based catalysts. Selected examples will show the synthesis and application in the field of organocatalysis and metal-based catalysis both for non-asymmetric and asymmetric transformations.

Hydroxyl-Exchanged Nanoporous Ionic Copolymer toward Low-Temperature Cycloaddition of Atmospheric Carbon Dioxide into Carbonates

An ionic copolymer catalyst with nanopores, large surface area, high ionic density, and superior basicity was prepared via the radical copolymerization of amino-functionalized ionic liquid bromide and divinylbenzene, followed with a hydroxyl exchange for removing bromonium. Evaluated in chemical fixation of CO2 with epoxides into cyclic carbonates in the absence of any solvent and basic additive, the nanoporous copolymer catalyst showed high and stable activity, superior to various control catalysts including the halogen-containing analogue. Further, high yields were obtained over a wide scope of substrates including aliphatic long carbon-chain alkyl epoxides and internal epoxide, even under atmospheric pressure and less than 100 °C for the majority of the substrates. On the basis of in situ Fourier transform infrared (FT-IR) investigation and density functional theory (DFT) calculation for the reaction intermediates, we proposed a possible reaction mechanism accounting for the superior catalytic activity of the ionic copolymer. The specifically prepared ionic copolymer material of this work features highly stable, noncorrosive, and sustainable catalysis and, thus, may be a new possibility for efficient chemical fixation of CO2 since it is an environmentally friendly, metal-free solid catalyst.

Nanoporous ionic organic networks: from synthesis to materials applications

This review highlights the recent progress made in the study of the synthesis of nanoporous ionic organic networks (NIONs) and their promising applications.

Fully-occupied Keggin type polyoxometalate as solid base for catalyzing CO2 cycloaddition and Knoevenagel condensation

A fully-occupied Keggin type polyoxometalate is proved to possess superior basicity and good basic activity for the first time.

Heterogeneous conversion of CO2 into cyclic carbonates at ambient pressure catalyzed by ionothermal-derived meso-macroporous hierarchical poly(ionic liquid)s

Meso-macroporous hierarchical poly(ionic liquid)s are ionothermally synthesized through self-polymerization of the new divinylimidazole IL, exhibiting enhanced CO₂ capture and excellent activity in the cycloaddition of CO₂ to epoxides.

Meso-macroporous hierarchical poly(ionic liquid)s (MPILs) with extremely high ionic site densities and tunable pore structures were ionothermally synthesized through the free radical self-polymerization of our newly designed rigid bis-vinylimidazolium salt monomer. The synthesis avoided the use of any templates, gave a high yield (>99%) and allowed recycling of the IL solvent; thus it is facile, atom-efficient, environmentally friendly and sustainable. The synthesized MPILs possessed distinctive features of polycation matrices, abundant halogen anions, and large surface areas. They not only presented enhanced CO₂ capture, but led to breakthroughs in the heterogeneous catalytic conversion of CO₂ into cyclic carbonates: (1) unprecedented high activity at atmospheric pressure and low temperature; (2) good substrate compatibility, even being active towards the extremely inert aliphatic long carbon-chain alkyl epoxides. This result renders the first occasion of a metal–solvent–additive free recyclable heterogeneous cycloaddition of CO₂ at such mild conditions.

Porous ionic liquids: synthesis and application

Solidification of fluidic ionic liquids into porous materials yields porous ionic networks that combine the unique characteristics of ionic liquids with the common features of polymers and porous materials. This minireview reports the most recent advances in the design of porous ionic liquids. A summary of the synthesis of ordered and disordered porous ionic liquid-based nanoparticles or membranes with or without templates is provided, together with the new concept of room temperature porous ionic liquids. As a versatile platform for functional materials, porous ionic liquids have shown widespread applications in catalysis, adsorption, sensing, actuation, etc. This new research direction towards ionic liquids chemistry is still in its early stages but has great potential.