Jiaojiao Song,Qianqian Meng,Jiang Wang,Xuling Guo,Ping Wei,Jinxiang Dong,Qi Shi
Most adsorbents have been developed for the separation of fermentation-derived butanol/acetone mixtures based on a thermodynamic mechanism. Butanol (8.4 Å × 5.5 Å) and acetone (6.4 Å × 5.8 Å) have similar molecular diameters, but different chain lengths. Thus, the objective of this work was to prepare and screen adsorbents for the separation of acetone/butanol mixtures based on a length exclusion mechanism. A number of ZIF-302 derivatives with adjustable cage sizes have been synthesized by adjusting the ratio between the small-sized mIm and large-sized mbIm links. The butanol and acetone separation performance of ZIF-302 derivatives was evaluated using static adsorption and dynamic column adsorption, which showed opposite selectivity. The ZIF-302-S4 adsorbent with large cages (9.6 Å × 6.6 Å) preferentially adsorbed long-chain butanol over short-chain acetone based on thermodynamic separation. By gradually increasing the proportion of the large-sized ligand in the ZIF-302 framework, the long axis size of the ellipsoidal cage was precisely adjusted and the corresponding ZIF-302-S2 adsorbent with small cages (6.5 Å × 6.6 Å) operated in an opposite way and preferentially adsorbed short-chain acetone over long-chain butanol based on length exclusion separation.
Haiqian Lian,Eryue Song,Bin Bao,Wenhe Yang,Yu Yang,Yichang Pan,Shengui Ju
Metal-organic frameworks (MOFs) as molecular sieve membrane materials have received extensive attention on the gas separation application. However, the membrane separation performance is extremely limited by its intrinsic stability of frameworks. The successful preparation of high-quality gas separation membranes with excellent stability remains a grand challenge. ZIF-302 is based on hydrophobic ligand in-situ design with a high-stabile chabazite (CHA) topology. Herein, we synthesized uniform ZIF-302 nanocrystals with exceptional stability by introducing a modulator. Correspondingly, the continuous dense ZIF-302 polycrystalline membranes were also prepared for the separation of H 2 , N 2 , CO 2 , CH 4 and other gases. The permeance of H 2 and separation factor for H 2 /CH 4 mixtures at 35 °C and 1 bar were 2.8 × 10 -8 mol m −2 s −1 Pa −1 and 51.5, respectively, exceeding the Robeson upper bound in 2008. Furthermore, the separation performance of the super-hydrophobic ZIF-302 membranes for humidified mixed gases can maintain more than 168 h at 35 °C, indicating reliable long-term operational stability. Therefore, the CHA-type ZIF-302 polycrystalline membrane is promising for actual industrial gas separation.
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