Basicity of isostructural porous ionic crystals composed of Nb/Ta-substituted Keggin-type polyoxotungstates

Zhewei Weng; Naoki Ogiwara; Daisuke Yokogawa; Takashi Kitao; Yuji Kikukawa; Sayaka Uchida

doi:10.1039/d2dt00478j

Basicity of isostructural porous ionic crystals composed of Nb/Ta-substituted Keggin-type polyoxotungstates

Dalton Trans. 2022 May 31;51(21):8186-8191. doi: 10.1039/d2dt00478j.

Authors

Zhewei Weng¹, Naoki Ogiwara¹, Daisuke Yokogawa¹, Takashi Kitao^{2

3}, Yuji Kikukawa⁴, Sayaka Uchida¹

Affiliations

¹ Department of Basic Science, School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan. csayaka@g.ecc.u-tokyo.ac.jp.
² Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
³ Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan.
⁴ Department of Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192, Japan.

PMID: 35475430
DOI: 10.1039/d2dt00478j

Abstract

Three isostructural porous ionic crystals (PICs) based on Keggin-type POMs with different compositions but equal negative charge ([BW₁₂O₄₀]^5- (BW12), [SiW₁₁NbO₄₀]^5- (SiW11Nb), and [SiW₁₁TaO₄₀]^5- (SiW11Ta)) are synthesized. Experimental and theoretical characterizations of the three PICs (1_BW12, 1_SiW11Nb, and 1_SiW11Ta) show that the substitution of Nb/Ta for W in the POMs enhances the basicity of PICs, which increases in the order of 1_BW12 < 1_SiW11Nb < 1_SiW11Ta. These findings clearly show that the increase in basicity is due not only to the increase in negative charge of the POM molecule as is often explained, but also to the character of the substituted element itself.