%0 Journal Article
%A Krause, Simon
%A Bon, Volodymyr
%A Du, Hongchu
%A Dunin-Borkowski, Rafal E
%A Stoeck, Ulrich
%A Senkovska, Irena
%A Kaskel, Stefan
%T The impact of crystal size and temperature on the adsorption-induced flexibility of the Zr-based metal-organic framework DUT-98
%J Beilstein journal of nanotechnology
%V 10
%@ 2190-4286
%C Frankfurt, M.
%I Beilstein-Institut zur Förderung der Chemischen Wissenschaften
%M FZJ-2020-02969
%P 1737-1744
%D 2019
%X 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%R 10.3762/bxiv.2019.52.v1
%U https://juser.fz-juelich.de/record/878641