Borohydride-containing coordination polymers: synthesis, air stability and dehydrogenation

Kentaro Kadota; Nghia Tuan Duong; Yusuke Nishiyama; Easan Sivaniah; Susumu Kitagawa; Satoshi Horike

doi:10.1039/c9sc00731h

Borohydride-containing coordination polymers: synthesis, air stability and dehydrogenation

Chem Sci. 2019 May 13;10(24):6193-6198. doi: 10.1039/c9sc00731h. eCollection 2019 Jun 28.

Authors

Kentaro Kadota¹, Nghia Tuan Duong², Yusuke Nishiyama^{2

3}, Easan Sivaniah^{1

4}, Susumu Kitagawa⁴, Satoshi Horike^{4

5

6

7}

Affiliations

¹ Department of Molecular Engineering , Graduate School of Engineering , Kyoto University , Katsura, Nishikyo-ku , Kyoto 615-8510 , Japan.
² RIKEN-JEOL Collaboration Center , Tsurumi , Yokohama , Kanagawa 230-0045 , Japan.
³ JEOL RESONANCE Inc. , Musashino , Akishima , Tokyo 196-8558 , Japan.
⁴ Institute for Integrated Cell-Material Sciences , Institute for Advanced Study , Kyoto University , Yoshida, Sakyo-ku , Kyoto 606-8501 , Japan . Email: horike@icems.kyoto-u.ac.jp.
⁵ AIST-Kyoto University Chemical Energy Materials Open Innovation Laboratory (ChEM-OIL) , National Institute of Advanced Industrial Science and Technology (AIST) , Yoshida-Honmachi, Sakyo-ku , Kyoto 606-8501 , Japan.
⁶ Department of Synthetic Chemistry and Biological Chemistry , Graduate School of Engineering , Kyoto University , Katsura, Nishikyo-ku , Kyoto 615-8510 , Japan.
⁷ Department of Materials Science and Engineering , School of Molecular Science and Engineering , Vidyasirimedhi Institute of Science and Technology , Rayong 21210 , Thailand.

Abstract

Control of the reactivity of hydride (H^-) in crystal structures has been a challenge because of its strong electron-donating ability and reactivity with protic species. For metal borohydrides, the dehydrogenation activity and air stability are in a trade-off, and control of the reactivity of BH₄ ^- has been demanded. For this purpose, we synthesize a series of BH₄ ^--based coordination polymers/metal-organic frameworks. The reactivity of BH₄ ^- in the structures is regulated by coordination geometry and neighboring ligands, and one of the compounds [Zn(BH₄)₂(dipyridylpropane)] exhibits both high dehydrogenation reactivity (1.4 wt% at 179 °C) and high air stability (50 RH% at 25 °C, 7 days). Single crystal X-ray diffraction analysis reveals that H ^δ+···H ^δ- dihydrogen interactions and close packing of hydrophobic ligands are the key for the reactivity and stability. The dehydrogenation mechanism is investigated by temperature-programmed desorption, in situ synchrotron PXRD and solid-state NMR.