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Scientists successfully prepared a molecular sieve membrane "thinner than a cicada's wing"

2014/12/12 01:57
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On December 12, a research team led by researchers Yang Weishen and Li Yanshuo of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences successfully prepared a molecular sieve membrane composed of 1 nanometer thick nanosheets for the first time. One-tenth, far "thinner than cicada's wings". The thickness of conventional molecular sieve membranes is more than ten times that of cicada wings. The nanosheets are not only extremely thin, but also have highly regular channels like "mesh holes", which can accurately screen hydrogen and carbon dioxide molecules with a size difference of only 0.04 nanometers, thereby effectively retaining the latter. The permeation flux and separation selectivity of the nanosheet molecular sieve membrane far exceed all hydrogen/carbon dioxide separation membranes reported in the literature, and it is the only membrane material that can meet the application requirements of carbon dioxide capture before combustion. The research results were published in "Science" (10.1126/science.1254227) on December 12.

The separation of hydrogen and carbon dioxide is a key step in clean energy and carbon dioxide capture. Using selective membrane materials to achieve the separation of the two at the molecular level has been a long-standing dream of the industry. For conventional membrane materials, there is a trade-off relationship between permeate flux and separation selectivity. Therefore, how to simultaneously improve the permeate flux and separation selectivity of separation membranes is an important challenge in the academic community.

Professor Y. Lin, deputy editor-in-chief of "Membrane Science" and a well-known American inorganic membrane scientist, commented that this research achievement is an important advance in the field of membrane science (A major advance in membrane science); a famous German molecular sieve membrane and membrane catalysis scientist Professor J. Caro evaluated the research as a ground-breaking work in the field of molecular sieve membranes; Professor T. Tsuru, chairman of the Japan Membrane Association and a famous microporous membrane scientist, evaluated the development of this research A new generation (A new generation) molecular sieve membrane.

The key to improving the permeation flux of the separation membrane is how to effectively reduce the membrane thickness; the key to improving the selectivity of the separation membrane is how to construct molecular-scale pores in the membrane. The research team of Dalian Institute of Chemical Physics, Chinese Academy of Sciences conducted a hydrothermal treatment of a widely studied zeolitic imidazolate framework (Zeolitic Imidazolate Frameworks, ZIFs), ZIF-7 nanoparticles, (Zn(bim)2, bim=benzimidazolate), and obtained The two-dimensional layered framework matrix material (Zn2(bim)4) with excellent stability, using methanol and n-propanol as dispersants, combined with ultra-low power wet ball milling and ultrasonic dispersion technology, successfully opened the layer for the first time in the world Metal Organic Frameworks (MOFs) nanosheets with monolayer thickness (~1nm) were prepared. On this basis, ultrathin molecular sieve membranes were obtained by thermal assembly method. The hydrogen/carbon dioxide separation coefficient of the nanosheet molecular sieve membrane reaches more than 200, and the hydrogen permeability reaches more than 2000 GPUs (1CPU=1 × 10-6 cm3/cm2·sec·cmHg, STP), which is much higher than the organic and inorganic materials reported so far. Hydrogen/carbon dioxide separation performance of membranes. The nanosheet molecular sieve membrane was tested for up to 400 hours under different heating and cooling conditions (room temperature to 200 oC) and hydrothermal conditions (150 oC), and the membrane performance remained unchanged.

In recent years, two-dimensional layered porous materials are becoming a research hotspot in the field of low-dimensional materials and nanoporous materials. The rich pore structure and tunable surface properties of two-dimensional MOFs provide an important platform for the directed design and synthesis of MOFs nanosheet molecular sieve membranes. This work demonstrates for the first time the important application of two-dimensional layered MOFs materials in the field of ultrathin molecular sieve membranes. The prepared nanosheet molecular sieve membrane is expected to play a practical role in the integrated coal gasification combined cycle (IGCC) system to realize the pre-combustion capture of carbon dioxide.

The research was supported by the National Natural Science Foundation of China and the Key Deployment Project of the Chinese Academy of Sciences.

Author: Li Yanshuo and Liu Wansheng Source: ScienceNet


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