open access

https://hdl.handle.net/2115/52883

Microporous cesium salts of tetravalent Keggin-type polyoxotungstates Cs-4[SiW12O40], Cs-4[PW11O39(Sn-n-C4H9)], and Cs-4[PW11O39(Sn-OH)] and their adsorption properties

英語

Anion defect

2013-07-01

Elsevier

Microporous and Mesoporous Materials

2013(174)

34-43

Microporous cesium salts of modified and unmodified tetravalent Keggin-type polyoxometalates, including Cs-4[SiW12O40], Cs-4[PW11O39(Sn-n-C4H9)], and Cs-4[PW11O39(Sn-OH)], were synthesized. The crystalline structures, which had body-centered cubic (bcc) arrangements, the lattice constants, and the pore-size distributions of the three Cs salts were similar, regardless of the presence or absence and types of functional groups introduced. The Cs salts had only micropores and no mesopores. The micropore size distributions were determined from adsorption isotherms of Ar, which showed a sharp peak at 0.59 nm and a shoulder at 0.62 nm. The fractions of the external surface areas to the total surface areas of the Cs salts were less than 6%. It is plausible that the micropores originate from the heteropoly anion defects in the crystallite, which form to avoid mismatches in the Cs+/(heteropoly anion) ratio required for charge balance (=4) and for a bcc structure (=3). The surface of the Cs salt introduced with n-butyl groups was hydrophobic, although the surface density of the n-butyl groups was low. On the other hand, the hydroxyl groups present on the surface of Cs-4[PW11O39(Sn-OH)] had little effect on the adsorption of water, methanol, ethanol, and hexane but a great impact on that for benzene due to the interactions between the -OH groups and the aromatic rings (-OH center dot center dot center dot pi). (C) 2013 Elsevier Inc. All rights reserved.

学術雑誌論文

Accepted Manuscript

1387-1811