As a well-known two-dimensional material, graphene exhibits preeminent electrical, mechanical and thermal properties owing to its unique one-atom-thick structure. Graphene and its derivatives (e.g., graphene oxide) become emerging nano-building blocks for separation membranes featuring distinct laminar structure and tunable physicochemical properties. Extraordinary molecular separation properties for purifying water and gases have been demonstrated by graphene-based membranes, which attract a huge surge of interest during last a few years 1. The pioneering work of Geim and co-workers found that laminar graphene oxide (GO) membranes are impermeable to gases and liquids but solely allow unimpeded evaporation of water. Thus, GO membranes have been reported for application in water-purification and solvent-dehydration processes 2. Meanwhile, recent works found that GO membranes can also exhibit gas-separation characteristics if their stacking structure is care-fully controlled 3. As the prominent characteristic of GO laminates, inter-layer space has been proved to play a significantly important role in molecular transport.
We are trying to tailor the nanospace between graphene oxide sheets for fast and selective transport of gases. Two approaches were demonstrated here. First, membranes with fast and selective CO2 transport channels of GO laminates were proposed based on the construction of hydrogen bonding between GO and polymer. Our explorations (e.g., TEM, positron annihilation) found that the formed molecular-sieving interlayer spacing and straight diffusion pathways of the GO laminates play critical roles in determining gas transport properties. Second, molecular-intercalated GO membranes were developed by a facile spin-casting assisted assembly technique. With a well-ordered stacking structure and enlarged interlayer spacing, the intercalated GO membranes show excellent molecular sieving properties. Our prepared GO membranes exhibited preferential CO2 (1st approach) or H2 (2ndapproach) permeation performance for gas mixtures that transcends the upper bounds of state-of-the-art membranes. Moreover, we firstly realized GO-based membranes having extraordinary operational stability, which is believed to be a notable step toward pushing this membrane into industrialized implementation.
Keywords: Graphene oxide, inter layer space, membrane, gas separation
The work was supported by the National Natural Science Foundation of China (Nos. 21406107, 2149580015, 21476107), Innovative Research Team Program by the Ministry of Education of China (No. IRT13070), Natural Science Foundation of Jiangsu Province (No. BK20140930).
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