Authors:
T. Haraguchi, K. Otsubo, O. Sakata, A. Fujiwara, H. Kitagawa

Abstract:
Fabrication of thin films made of metal–organic frameworks (MOFs) has been intensively pursued for practical applications that use the structural response of MOFs. However, to date, only physisorption-induced structural response has been studied in these films. Chemisorption can be expected to provide a remarkable structural response because of the formation of bonds between guest molecules and reactive metal sites in host MOFs. Here, we report that chemisorption-induced two-way structural transformation in a nanometer-size MOF thin film. We prepared a two-dimensional layered-type MOF Fe[Pt(CN)4] thin film using a step-by-step approach. Although the as-synthesized film showed poor crystallinity, the dehydrated form of this thin film had a highly oriented crystalline nature (Film-D) as confirmed by synchrotron X-ray diffraction (XRD). Surprisingly, under water and pyridine vapors, Film-D showed chemisorption-induced dynamic structural trans-formations to Fe(L)2[Pt(CN)4] thin films [L = H2O (Film-H), pyridine (Film-P)], where water and pyridine coordinated to open the Fe2+ site. Dynamic structural transformations were also confirmed by in situ XRD, sorption measurement, and infrared reflection absorption spectroscopy. This is the first report of chemisorption-induced dynamic structural response in a MOF thin film, and it provides useful insights, which would lead to future practical applications of MOFs utilizing chemisorption-induced structural responses.

Link:
J. Am. Chem. Soc. 138 (2016) 16787–16793.
DOI: 10.1021/jacs.6b10913