TY  - JOUR
AU  - Krause, Simon
AU  - Bon, Volodymyr
AU  - Du, Hongchu
AU  - Dunin-Borkowski, Rafal E
AU  - Stoeck, Ulrich
AU  - Senkovska, Irena
AU  - Kaskel, Stefan
TI  - The impact of crystal size and temperature on the adsorption-induced flexibility of the Zr-based metal–organic framework DUT-98
JO  - Beilstein journal of nanotechnology
VL  - 10
SN  - 2190-4286
CY  - Frankfurt, M.
PB  - Beilstein-Institut zur Förderung der Chemischen Wissenschaften
M1  - FZJ-2020-02774
SP  - 1737 - 1744
PY  - 2019
AB  - In this contribution we analyze the influence of adsorption cycling, crystal size, and temperature on the switching behavior of the flexible Zr-based metal–organic framework DUT-98. We observe a shift in the gate-opening pressure upon cycling of adsorption experiments for micrometer-sized crystals and assign this to a fragmentation of the crystals. In a series of samples, the average crystal size of DUT-98 crystals was varied from 120 µm to 50 nm and the obtained solids were characterized by X-ray diffraction, infrared spectroscopy, as well as scanning and transmission electron microscopy. We analyzed the adsorption behavior by nitrogen and water adsorption at 77 K and 298 K, respectively, and show that adsorption-induced flexibility is only observed for micrometer-sized crystals. Nanometer-sized crystals were found to exhibit reversible type I adsorption behavior upon adsorption of nitrogen and exhibit a crystal-size-dependent steep water uptake of up to 20 mmol g−1 at 0.5 p/p0 with potential for water harvesting and heat pump applications. We furthermore investigate the temperature-induced structural transition by in situ powder X-ray diffraction. At temperatures beyond 110 °C, the open-pore state of the nanometer-sized DUT-98 crystals is found to irreversibly transform to a closed-pore state. The connection of crystal fragmentation upon adsorption cycling and the crystal size dependence of the adsorption-induced flexibility is an important finding for evaluation of these materials in future adsorption-based applications. This work thus extends the limited amount of studies on crystal size effects in flexible MOFs and hopefully motivates further investigations in this field.
LB  - PUB:(DE-HGF)16
C6  - pmid:31501745
UR  - <Go to ISI:>//WOS:000482478100001
DO  - DOI:10.3762/bjnano.10.169
UR  - https://juser.fz-juelich.de/record/878318
ER  -