Impact of Crystal Size and Morphology on Switchability Characteristics in Pillared-Layer Metal-Organic Framework DUT-8(Ni)

Abstract

Variation of the crystallite size in flexible porous coordination polymers can significantly influence or even drastically change the flexibility characteristics. The impact of crystal morphology, however, on the dynamic properties of flexible metal-organic frameworks (MOFs) is poorly investigated so far. In the present work, we systematically modulated the particle size of a model gate pressure MOF (DUT-8(Ni), Ni2(2,6-ndc)2(dabco), 2,6-ndc−2,6-naphthalenedicarboxylate, dabco−1,4-diazabicyclo[2.2.2]octane) and investigated the influence of the aspect ratio, length, and width of anisotropically shaped crystals on the gate opening characteristics. DUT-8 is a member of the pillared-layer MOF family, showing reversible structural transition, i.e., upon nitrogen physisorption at 77 K. The framework crystalizes as rod-like shaped crystals in conventional synthesis. To understand which particular crystal surfaces dominate the phenomena observed, crystals similar in size and differing in morphology were involved in a systematic study. The analysis of the data shows that the width of the rods (corresponding to the crystallographic directions along the layer) represents a critical parameter governing the dynamic properties upon adsorption of nitrogen at 77 K. This observation is related to the anisotropy of the channel-like pore system and the nucleation mechanism of the solid-solid phase transition triggered by gas adsorption.

The importance of crystal size for breathing kinetics in MIL-53(Al)

“…Preservation of the metastable porous, open pore phase after desorption of guests in the nanocrystalls was denoted by authors as a shape-memory effect. 28 Later, the strong dependency of flexibility on the crystal size was observed in many other flexible frameworks such as ZIF-8, 29 DUT-8, 30 DUT-49. 31 In general, crystal size and morphology strongly influence flexibility in MOFs, showing general trend towards rigidification of the framework with reducing crystal size.…”

Isotope-selective pore opening in a flexible metal-organic framework

“…1A). Crystal size, morphology, and conformation are used to effectively tune the responsivity of DUT-8(Ni) ( 35 , 36 ). While macrosized DUT-8(Ni) crystals show selective guest responsivity associated with a pronounced cell volume change (~250%) upon gate opening [an adsorption-induced transition from a closed-pore (cp) to an open-pore (op) phase triggered by nitrogen, carbon dioxide, or C2-C4 hydrocarbons at their standard boiling points ( 37 )], nanocrystals of DUT-8(Ni) are rigid instead and show reversible uptake of gasses after desolvation.…”

Enhancing the energy storage performances of metal–organic frameworks by controlling microstructure

“…This method has been successfully employed in previous studies to determine the impact of particle morphology on the physical properties of other MOFs. [26][27][28] Drawing on the above, this work uses coordination modulation to synthesise three samples of the layered conductive MOF Cu 3 (HHTP) 2 , (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene), each with distinctly different microstructures. This approach leads to greater differences in sample microstructure than previous work on this topic, with a variation in the length-to-width aspect ratio over the range of ca.…”

“…This method has been successfully employed in previous studies to determine the impact of particle morphology on the physical properties of other MOFs. 26–28…”