The inherent structure tunability, good affinity with CO, and nonvolatility of ionic liquids (ILs) drive their exploration and exploitation in CO separation field, and has attracted remarkable interest from both industries and academia. The aim of this Review is to give a detailed overview on the recent advances on IL-based materials, including pure ILs, IL-based solvents, and IL-based membranes for CO capture and separation from the viewpoint of molecule to engineering. The effects of anions, cations and functional groups on CO solubility and selectivity of ILs, as well as the studies on degradability of ILs are reviewed, and the recent developments on functionalized ILs, IL-based solvents, and IL-based membranes are also discussed. CO separation mechanism with IL-based solvents and IL-based membranes are explained by combining molecular simulation and experimental characterization. Taking into consideration of the applications and industrialization, the recent achievements and developments on the transport properties of IL fluids and the process design of IL-based processes are highlighted. Finally, the future research challenges and perspectives of the commercialization of CO capture and separation with IL-based materials are posed.

The ever-increasing demands for clean and sustainable energy sources combined with rapid advances in bio-integrated portable or implantable electronic devices have stimulated intensive research activities in enzymatic (bio)fuel cells (EFCs). The use of renewable biocatalysts, the utilization of abundant green, safe, and high energy density fuels, together with the capability of working at modest and biocompatible conditions, make EFCs promising as next generation alternative power sources. However, the main challenges (low energy density, relatively low power density, poor operational stability and limited voltage output) hinder future applications of EFCs. This review aims at exploring the underlying mechanism of EFCs and providing possible practical strategies, methodologies and insights to tackle of these issues. Firstly, this review summarizes approaches in achieving high energy densities in EFCs, particularly, employing enzyme cascades for the deep/complete oxidation of fuels. Secondly, strategies for increasing power densities in EFCs, including increasing enzyme activities, facilitating electron transfers, employing nanomaterials, and designing more efficient enzyme-electrode interfaces, are described. The potential of EFCs/(super)capacitor combination is discussed. Thirdly, the review evaluates a range of strategies for improving the stability of EFCs, including the use of different enzyme immobilization approaches, tuning enzyme properties, designing protective matrixes, and using microbial surface displaying enzymes. Fourthly, approaches for the improvement of the cell voltage of EFCs are highlighted. Finally, future developments and a prospective on EFCs are envisioned.

In this work, three kinds of ether-functionalized pyridinium-based ILs [E n Py]­[NTf2] with low viscosity were designed and synthesized and used for highly selective separation of CO2 from CH4. It was found that the ether groups play an important role on physicochemical properties and CO2/CH4 selectivity in these three ILs. Compared with the nonfunctionalized analogues [C m Py]­[NTf2], the viscosities of [E n Py]­[NTf2] are lower and obviously decrease with the increasing number of ether oxygen atoms. The presence of ether groups on the cation has weak impacts on CO2 solubility of the ILs, but it contributes to a much lower CH4 solubility, which leads to the great increase of CO2/CH4 selectivity using [E n Py]­[NTf2]. Moreover, CO2/CH4 selectivity in all investigated ILs greatly decreases with the increasing temperature due to the weaker temperature dependence of CH4 solubility. In addition, the thermodynamic properties including the Gibbs free energy, enthalpy, and entropy of CO2 and CH4 in these ILs were also obtained, and the CO2 and CH4 dissolution mechanisms were further analyzed. The results demonstrated that the gas–IL interaction plays a dominate role in CH4 solubility in the investigated ILs, but CO2 dissolution in ILs is determined by both the IL–gas interaction and free volume of ILs. This work will offer new insights into designing more competitive ILs for selective separation of CO2 from CH4.

Carbon molecular sieve (CMS) membranes with rigid and uniform pore structures are ideal candidates for high temperature- and pressure-demanded separations, such as hydrogen purification from the steam methane reforming process. Here, we report a facile and scalable method for the fabrication of cellulose-based asymmetric carbon hollow fiber membranes (CHFMs) with ultramicropores of 3–4 Å for superior H2 separation. The membrane fabrication process does not require complex pretreatments to avoid pore collapse before the carbonization of cellulose precursors. A H2/CO2 selectivity of 83.9 at 130 °C (H2/N2 selectivity of >800, H2/CH4 selectivity of >5700) demonstrates that the membrane provides a precise cutoff to discriminate between small gas molecules (H2) and larger gas molecules. In addition, the membrane exhibits superior mixed gas separation performances combined with water vapor- and high pressure-resistant stability. The present approach for the fabrication of high-performance CMS membranes derived from cellulose precursors opens a new avenue for H2-related separations.

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