Metal organic framework (MOF) has been recognized as a fascinating class of solid crystalline materials which can be built with metal ions (or clusters) and organic linkers. Owing to their versatile chemical and engineering design, the more attention for MOF is shifting from its fundamental studies to industrial application including membrane separation. This review discusses recent progress in MOF–based membranes and the challenges and opportunities for future membrane separation technology.

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Atmospheric–pressure plasma–enhanced chemical vapor deposition (AP–PECVD) is an innovative technology, which enables the fabrication of silica–based membranes at ambient temperature and pressure. In this paper, the fabrication of microporous inorganic membranes via low–pressure PECVD is summarized, and then, the development of AP–PECVD system for the fabrication of silica–based membranes is presented. By using AP–PECVD technique, highly permselective silica–based membranes were successfully fabricated. It was revealed that the gas permeation property of AP–PECVD–derived membranes could be controlled by changing membrane preparation parameters such as plasma reaction atmosphere, precursor species, and annealing temperature. Finally, research challenges and opportunities in AP–PECVD will be highlighted.

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Ionic liquids (ILs) have been used in membrane separation for more than a decade due to their physical and chemical properties, such as non–volatility, thermal stability and ability to dissolve CO₂ and a large range of organic molecules. In this paper, we present a new concept in chemically stabilized IL membranes which is an organosilica membrane using a silylated IL as a precursor chemical. The membranes showed selective permeability toward organic vapors against H₂ with improved durability over supported IL membranes. Their permeation and separation mechanism, and microstructure were discussed by gas and vapor permeation tests, Attenuated Total Reflection –IR, and N2 adsorption measurements.

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Polymeric reverse osmosis (RO) membranes are widely used for practical desalination processes. They are promised ways to separate water molecules from feed solutions effectively, although they have already reached a limitation in improvement of water permeability. On biological cell membranes, some kinds of water channel molecules, such as membrane proteins and peptides, effectively and selectively transport water molecules through lipid bilayers, while lipid bilayers prevent the permeation of various molecules through the membrane. Recently, biomimetic approaches using biological water channel, aquaporin, have attracted attentions to fabricate highly water–permeable RO membranes. In this report, the recent progress of the development of biomimetic RO membranes was summarized.

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Biological membranes possess sophisticated functionalities such as selective ion and water molecule transport, signal transduction, reaction field, and so on. “Bioinspired material” is a material that reconstructs such functionalities artificially. As such material, gating membrane exhibited ON/OFF switching behavior in response to external stimuli, e.g. temperature, pH, electric field, magnetic field, and specific ions and molecules. This kind of bioinspired channel can be fabricated by grafting stimuli–responsive polymer onto the pore surface of porous substrate. To attain steeper gating behavior, the grafted polymer should be long enough for filling the pore in OFF state. The plasma graft polymerization technique can fabricate graft polymer with ultra–high molecular weight more than 1,000,000 g/mol. Furthermore, by grafting the ultra–high molecular weight ion recognition polyampholyte on the porous substrate, specific membrane that can control its permeability in response to both of pH and specific ion (such as K+ and Ba2+) can be fabricated. In the present study, the fabrication mechanism of the ultra–high molecular weight graft polymer, and specific behavior of the ion recognition polyampholyte membrane is reported.

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The history in the usage of porous materials in filtering and separating impurity materials is very old. Nowadays porous materials are used in industrial application and are essential in the world. Discussed in this article is the different methods in measuring the through pore size distribution of porous media which is the key factor in deciding the comparative merits of the filtering and separating of the media. The bubble point theory is a well–known method in measuring the neck pore size distribution of samples. We will describe the liquid–liquid porometry technique in expanding the lower limit of the bubble point theory and the latest approaches on how the data acquisition has been improved in the testing to get the most reproducible and reliable data.

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