To prevent greenhouse emissions into the atmosphere, separations like CO2/CH4 and CO2/N2 from natural gas, biogas, and flue gasses are crucial. Polymer membranes gained a key role in gas separations over the past decades, but these polymers are often not organized at a molecular level, which results in a trade-off between permeability and selectivity. In this work, the effect of molecular order and orientation in liquid crystals (LCs) polymer membranes for gas permeation is demonstrated. Using the self-assembly of polymerizable LCs to prepare membranes ensures control over the supramolecular organization and alignment of the building blocks at a molecular level. Robust freestanding LC membranes were fabricated that have various, distinct morphologies (isotropic, nematic cybotactic, and smectic C) and alignment (planar and homeotropic), while using the same chemical composition. Single gas permeation data show that the permeability decreases with increasing molecular order while the ideal gas selectivity of He and CO2 over N2 increases tremendously (36-fold for He/N2 and 21-fold for CO2/N2) when going from randomly ordered to the highly ordered smectic C morphology. The calculated diffusion coefficients showed a 10-fold decrease when going from randomly ordered membranes to ordered smectic C membranes. It is proposed that with increasing molecular order, the free volume elements in the membrane become smaller, which hinders gasses with larger kinetic diameters (Ar, N2) more than gasses with smaller kinetic diameters (He, CO2), inducing selectivity. Comparison of gas sorption and permeation performances of planar and homeotropic aligned smectic C membranes shows the effect of molecular orientation by a 3-fold decrease of the diffusion coefficient of homeotropic aligned smectic C membranes resulting in a diminished gas permeation and increased ideal gas selectivities. These results strongly highlight the importance of molecular order and orientation in LC polymer membranes for gas separation.

Microfluidic devices allow the manipulation of fluids down to the micrometer scale and are receiving a lot of attention for applications where low volumes and high throughputs are required. In these micro channels, laminar flow usually dominates, which requires long residence times of the fluids, limiting the flow speed and throughput. Here a switchable passive mixer has been developed to control mixing and to easily clean microchannels. The mixer is based on a photoresponsive spiropyran based hydrogel of which the dimensions can be tuned by changing the intensity of the light. The size-tunable gels have been used to fabricate a passive slanted groove mixer that can be switched off by light allowing to change mixing of microfluidics to non-mixed flows. These findings open new possibilities for multi-purpose microfluidic devices where mixers and valves can be tuned by light.

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Back Cover: The cover image depicts a light‐responsive, passive micromixer in its swollen state, which mixes blue and yellow fluids using slanted groove structures. The molecule on the left is a protonated merocyanine, resulting in a swollen hydrogel, illustrated by the yellow disk. When illuminated, the spiropyran on the right is formed, resulting in a collapsed hydrogel, illustrated by the white disk. Further details can be found in article number https://doi.org/10.1002/marc.201700086 by Jaap M. J. den Toonder,* Albertus P. H. J. Schenning,* and co‐workers. The cover was designed by Mats Björklund.

organic linkers. The obtained ordered organic-inorganic networks exhibit high surface areas and their pore size, aperture and functionality is highly tunable, due to the variability in available organic linkers. [1] For example, a series of iron(III) carboxylate MOFs shows varying framework flexibility, pore size, pore aperture, and 3D structure by varying the carboxylate linker type. [2-6] These properties make MOFs very attractive materials in the field of gas storage and separation, since gas sorption and diffusion are tunable by linker variation. [7,8] Despite these promising characteristics, MOFs often lack chemical and thermal stability, which limits their practical application. Nonetheless, the number of stable MOFs has been increasing over the years. [9] One subclass of thermally and chemically stable MOFs are zeolitic imidazolate frameworks (ZIFs), which consist out of zinc or cobalt cations and a variety of imidazolate linkers. Since the first reported ZIFs, many new ZIF structures and topologies have been unraveled. [10] Due to their versatility, stability, and microporous nature (i.e., high gas uptake), multiple ZIF containing membrane structures have been investigated for gas separation purposes. [11,12] By the use of high-throughput synthesis, ZIF structures analogous to the zeolite gmelinite (GME) topology were found, which exhibited extraordinary high CO 2 uptake. [13] These hexagonal anisotropic GME ZIF crystals have two 1D channel types (one pore exists out of KNO cages, with pore apertures ranging from 4.5 to 8 Å, the other out of alternating GME and HPR cages, with pore apertures ranging from 3.6 to 4.3 Å) that are oriented parallel along the c-axis of the crystal structure (Figure 1). [14,15] GME ZIFs are constructed by linking Zn 2+ with 2-nitroimidazolate (nIm) and another imidazolate linker, where the other imidazolate linker determines the pore size, aperture, and polarity. [13,14] Controlling size and shape of the mixed linker ZIFs is rather difficult, since the difference in pK a values between the variable imidazoles and 2-nitroimidazole (nIm) causes different degrees of deprotonation in the reaction mixture. [16] Nonetheless, for ZIF-69 and 78 (both with GME topology) it was shown that their size and aspect ratio could be controlled by using specific zinc salts and deprotonating agents and adapting the ratio between zinc and the imidazoles. [17-19] In this work, the influence of the zeolitic imidazolate framework 78 (ZIF-78) morphology, with 1D pores, on the mixed matrix membrane (MMM) CO 2 /N 2 mixed gas separation performance is investigated as well as the influence of the feed composition and pressure. Low aspect ratio and a high aspect ratio ZIF-78 particles are synthesized and incorporated in Matrimid with 10 and 20 wt% additive content. High pressure CO 2 and N 2 sorption measurements show that both the low and high aspect ratio ZIF-78 metal-organic frameworks (MOFs) exhibit similar sorption behavior. The incorporation of ZIF-78 into Matrimid results in improved CO 2 permeabilit...