Chitosan-Linked Dual-Sulfonate COF Nanosheet Proton Exchange Membrane with High Robustness and Conductivity.

2D materials that can provide long-range ordered channels in thin-film form are highly desirable for proton exchange membranes (PEMs). Covalent organic framework nanosheets (CONs) are promising 2D materials possessing intrinsic porosity and high processability. However, the potential of CONs in PEMs is limited by loose sheet stacking and interfacial grain boundary, which lead to unsatisfied mechanical property and discontinuous conduction pathway. Herein, chitosan (CS), a natural polymer with rich NH2 groups, is designed as the linker of dual-sulfonate CONs (CON-2(SO3 H)) to obtain CON-2(SO3 H)-based membrane. Ultrathin CON-2(SO3 H) with high crystallinity and large lateral size is synthesized at water-octanoic acid interface. The high flexibility of CS chains and their electrostatic interactions with SO3 H groups of CON-2(SO3 H) enable effective connection of CON-2(SO3 H), thus endowing membrane dense structure and exceptional stability. The stacked CON-2(SO3 H) constructs regular hydrophilic nanochannels containing high-density SO3 H groups, and the electrostatic interactions between CON-2(SO3 H) and CS form interfacial acid-base pairs transfer channels. Consequently, CON-2(SO3 H)@CS membrane simultaneously achieves superior proton conductivity of 353 mS cm-1 (under 80 °C hydrated condition) and tensile strength of 95 MPa. This work highlights the advantages of proton-conducting porous CON-2(SO3 H) in advanced PEMs and paves a way in fabricating robust CON-based membranes for various applications.

Ether- and alcohol-functionalized task-specific ionic liquids: attractive properties and applications.

In recent years, the designer nature of ionic liquids (ILs) has driven their exploration and exploitation in countless fields among the physical and chemical sciences. A fair measure of the tremendous attention placed on these fluids has been attributed to their inherent designer nature. And yet, there are relatively few examples of reviews that emphasize this vital aspect in an exhaustive or meaningful way. In this critical review, we systematically survey the physicochemical properties of the collective library of ether- and alcohol-functionalized ILs, highlighting the impact of ionic structure on features such as viscosity, phase behavior/transitions, density, thermostability, electrochemical properties, and polarity (e.g. hydrophilicity, hydrogen bonding capability). In the latter portions of this review, we emphasize the attractive applications of these functionalized ILs across a range of disciplines, including their use as electrolytes or functional fluids for electrochemistry, extractions, biphasic systems, gas separations, carbon capture, carbohydrate dissolution (particularly, the (ligno)celluloses), polymer chemistry, antimicrobial and antielectrostatic agents, organic synthesis, biomolecular stabilization and activation, and nanoscience. Finally, this review discusses anion-functionalized ILs, including sulfur- and oxygen-functionalized analogs, as well as choline-based deep eutectic solvents (DESs), an emerging class of fluids which can be sensibly categorized as semi-molecular cousins to the IL. Finally, the toxicity and biodegradability of ether- and alcohol-functionalized ILs are discussed and cautiously evaluated in light of recent reports. By carefully summarizing literature examples on the properties and applications of oxy-functional designer ILs up till now, it is our intent that this review offers a barometer for gauging future advances in the field as well as a trigger to spur further contemplation of these seemingly inexhaustible and--relative to their potential--virtually untouched fluids. It is abundantly clear that these remarkable fluidic materials are here to stay, just as certain design rules are slowly beginning to emerge. However, in fairness, serendipity also still plays an undeniable role, highlighting the need for both expanded in silico studies and a beacon to attract bright, young researchers to the field (406 references).

In Situ-Doped Sulfonated Schiff-Base Networks in SPEEK Composite Membranes with Enhanced Proton Conductivity.

Sulfonated polyether ether ketone (SPEEK) has been widely investigated in proton exchange membrane fuel cells (PEMFCs) due to its excellent thermal stability, chemical stability, and low cost compared with Nafion. However, excessive degree of sulfonation will easily lead to the decrease in thermal stabilities and mechanical properties of SPEEK membranes, which limits the enhancement of proton conductivity. In this work, a series of Schiff-base networks (SNWs) with different contents are in situ synthesized in the SPEEK membrane by a Schiff-base co-condensation reaction, and then, the composite membranes are soaked in sulfonic acid for further improvement of proton conductivity. The highest doping amount of the SNW filler in SPEEK can reach 20 wt %. High loading and low leaching rate of H2SO4 are easily achieved owing to the similar size between sulfuric acid molecules and micropores in SNW. Moreover, abundant amino and imine groups in SNW networks contribute to the anchoring of H2SO4 into the pores by acid-base interactions. The proton conductivity of the SPEEK/S-SNW-15 composite membrane can reach 115.53 mS cm-1 at 80 °C and 100% RH. Meanwhile, the composite membrane also exhibits satisfied stability and mechanical property.

Amino-Functionalized Ionic-Liquid-Grafted Covalent Organic Frameworks for High-Efficiency CO2 Capture and Conversion.

Rationally integrating desired functional components into a composite material can endow the tailored function to achieve the corresponding purpose. This is the first case where a series of [AeImBr]X%-TAPT-COFs (X = 0, 17, 33, 50, 67, 83, 100) were fabricated by chemically integrating the amino-functionalized imidazole ionic liquid (NH2-IL) onto channel walls of mesoporous covalent organic framework materials ([HO]X%-TAPT-COFs). By virtue of the polar groups (amino groups) and abundant imidazole cations of NH2-IL and its microporous nature, the obtained [AeImBr]X%-TAPT-COFs exhibit higher CO2 capture activity than [HO]X%-TAPT-COFs. Correspondingly, the CO2 equilibrium capture capacity increases from 62.6 to 117.4 mg/g, which is crucial to the storage of enough CO2 around the catalytic active sites. Additionally, the synergistic effect of -NH2 and Br- in NH2-IL can also improve the cycloaddition reaction rate. The characteristics of [AeImBr]X%-TAPT-COFs contribute to the efficient generation of cyclic carbonate through heterogeneously catalyzing CO2-epoxide cycloaddition without any solvents and cocatalysts. Specifically, [AeImBr]83%-TAPT-COF has a CO2 equilibrium capture capacity of 117.4 mg/g and cyclochloroallyl carbonate yield of 99.1%. As a result of the use of the chemical grafting method, [AeImBr]X%-TAPT-COFs possess excellent stability and cycle life. The equilibrium capture capacity and cyclochloroallyl carbonate yield reach 112.7 mg CO2/g adsorbent and 95.0% at the eighth cycle.

Novel Quaternary Ammonium-Functionalized Covalent Organic Frameworks/Poly(2,6-dimethyl-1,4-phenylene oxide) Hybrid Anion Exchange Membranes with Enhanced Ion Conductivity and Stability.

Here we report a new hybrid anion exchange membrane with enhanced hydroxide conductivity and excellent chemical and dimensional stability by incorporating quaternary ammonium (QA)-functionalized covalent organic framework into brominated poly(2,6-dimethyl-1,4-phenylene oxide) (BPPO). N,N,N',N' -Tetramethyl-1,6-hexanediamine (TMHDA) was impregnated into the pores of COF-LZU1 via a vacuum-assisted method, followed by reacting with allyl bromide. The generated QA groups were immobilized within the highly ordered pores of COF-LZU1 via in situ polymerization, forming long-range ordered multiple ion channels. The obtained QA@COF-LZU1 was then mixed with QAPPO to construct a hybrid anion exchange membrane for anion exchange membrane fuel cells (AEMFCs). The hydroxide conductivity of QA@COF-LZU1/PPO hybrid membrane increased up to 168.00 mS cm-1 at 80 °C, about 77% higher than that of pristine membrane. In addition, alkaline stability and thermal stability of the hybrid membranes were obviously enhanced. The excellent performance and the outstanding chemical stability render the COF hybrid membrane a good candidate for the application in AEMFCs.

Biocatalytic synthesis of vitamin A palmitate using immobilized lipase produced by recombinant Pichia pastoris.

In this work, the Candida antarctica lipase B (CALB), produced by recombinant Pichia pastoris, was immobilized and used to synthesize vitamin A palmitate by transesterification of vitamin A acetate and palmitic acid in organic solvent. The reaction conditions including the type of solvent, temperature, rotation speed, particle size, and molar ratio between the two substrates were investigated. It turned out that the macroporous resin HPD826 serving as a carrier showed the highest activity (ca. 9200 U g-1) among all the screened carriers. It was found that the transesterification kinetic of the immobilized CALB followed the ping pong Bi-Bi mechanism and the reaction product acetic acid inhibited the enzymatic reaction with an inhibition factor of 2.823 mmol L-1. The conversion ability of the immobilized CALB was 54.3% after 15 cycles. In conclusion, the present work provides a green route for vitamin A palmitate production using immobilized CALB to catalyze the transesterification of vitamin A acetate and palmitic acid.

Glymes as Versatile Solvents for Chemical Reactions and Processes: from the Laboratory to Industry.

Glymes, also known as glycol diethers, are saturated non-cyclic polyethers containing no other functional groups. Most glymes are usually less volatile and less toxic than common laboratory organic solvents; in this context, they are more environmentally benign solvents. However, it is also important to point out that some glymes could cause long-term reproductive and developmental damages despite their low acute toxicities. Glymes have both hydrophilic and hydrophobic characters that common organic solvents are lack of. In addition, they are usually thermally and chemically stable, and can even form complexes with ions. Therefore, glymes are found in a broad range of laboratory applications including organic synthesis, electrochemistry, biocatalysis, materials, and Chemical Vapor Deposition (CVD), etc. In addition, glyme are used in numerous industrial applications, such as cleaning products, inks, adhesives and coatings, batteries and electronics, absorption refrigeration and heat pumps, as well as pharmaceutical formulations, etc. However, there is a lack of comprehensive and critical review on this attractive subject. This review aims to accomplish this task by providing an in-depth understanding of glymes' physicochemical properties, toxicity and major applications.

Glymes as new solvents for lipase activation and biodiesel preparation.

Glymes (i.e. glycol diethers) were explored as alternative benign solvents for enzymatic reactions, specifically the lipase-catalyzed transesterification. Long-chain glymes were found highly compatible with immobilized Candida antarctica lipase B (iCALB), leading to higher enzyme activities and stabilities than t-butanol and ionic liquids (e.g. the rate of transesterification in diethylene glycol dibutyl ether (G2-Bu) was 77% higher than that in t-butanol). Furthermore, soybean oil was found fully miscible with glymes, which enabled a homogeneous reaction mixture for the enzymatic preparation of biodiesel. In the presence of glymes, CALB showed a very high tolerance to high methanol concentrations (up to 60-70% v/v), and nearly stoichiometric triglyceride conversions could be obtained under mild reaction conditions. A laboratory scale-up achieved a high conversion of soybean oil (95.5%). This study suggests that glymes can be environmentally friendly and inexpensive solvents for lipase-catalyzed reactions, such as the enzymatic preparation of biodiesel.

Glymes as benign co-solvents for CaO-catalyzed transesterification of soybean oil to biodiesel.

The base (such as CaO)-catalyzed heterogeneous preparation of biodiesel encounters a number of obstacles including the need for CaO pretreatment and the reactions being incomplete (typically 90-95% yields). In this study, a number of glymes were investigated as benign solvents for the CaO-catalyzed transesterification of soybean oil into biodiesel with a high substrate loading (typically soybean oil >50% v/v). The triglyceride-dissolving capability of glymes led to a much faster reaction rate (>98% conversions in 4h) than in methanol alone (typically 24h) and minimized the saponification reaction when catalyzed by anhydrous CaO or commercial lime without pre-activation. The use of glyme (e.g. P2) as co-solvent also activates commercial lime to become an effective catalyst without calcination pretreatment. The SEM images suggest a dissolution-agglomeration process of CaO surface in the presence of P2, which could remove the CaCO3 and Ca(OH)2 layer coated on the surface of lime.

Enantiomer separations on a vancomycin stationary phase and retention mechanism of pressurized capillary electrochromatography.

Several chiral drugs, promethazine, carteolol, celiprolol, and albuterol, were resolved with vancomycin as the chiral stationary phase by pressurized capillary electrochromatography (pressurized CEC) and capillary HPLC. The effects of pressure and electrical field strength on efficiency, resolution, and capacity factor in pressurized CEC were investigated. A mathematical model describing the relationship of capacity factor in pressurized CEC with voltage, pressurized flow velocity, electroosmotic mobility, and electrophoretic mobility was established, which was in good agreement with the experimental data.