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-2020-02969
SP  - 1737-1744
PY  - 2019
AB  - In this contribution we analyse the influence of adsorption cycling, crystal size, and temperature on the switching behaviour of the flexible Zr-based metal-organic framework DUT-98. We observe a shift in the gate opening pressure upon cycling of adsorption experiments of micro meter-sized crystals and assign this to a fragmentation of the crystals. In a series of modulated syntheses we downsize the average crystal size of DUT-98 crystals from 120 µm to 50 nm and characterize the obtained solids by X-ray diffraction, infrared spectroscopy, as well as scanning and transmission electron microscopy. We analyse the adsorption behaviour by nitrogen and water adsorption at 77 K and 298 K, respectively and show that adsorption-induced flexibility is only observed for micro meter-sized crystals. Nanometer-sized crystals were found to exhibit reversible type I adsorption behaviour upon adsorption of nitrogen and exhibit a crystal-size dependent steep water uptake of up to 20 mmol g -1 at 0.5  p / p 0 with potential for water harvesting and heat pump applications. We furthermore investigate the temperature-induced structural transition by in situ PXRD. At temperatures beyond 110 °C the open pore state of nano meter-sized DUT-98 crystals are found to irreversibly transform in 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 into this field.
LB  - PUB:(DE-HGF)16
DO  - DOI:10.3762/bxiv.2019.52.v1
UR  - https://juser.fz-juelich.de/record/878641
ER  -