Tuning the gate-opening pressure and particle size distribution of the switchable metal–organic framework DUT-8(Ni) by controlled nucleation in a micromixer

Abstract

Controlled nucleation in a micromixer and further crystal growth were used to synthesize Ni(2,6-ndc)dabco (2,6-ndc - 2,6-naphthalenedicarboxylate, dabco - 1,4-diazabicyclo[2.2.2]octane), also termed DUT-8(Ni) (DUT = Dresden University of Technology), with narrow particle size distribution in a range of a few nm to several μm. The crystal size was found to significantly affect the switching characteristics, in particular the gate opening pressure in nitrogen adsorption isotherms at 77 K for this highly porous and flexible network. Below a critical size of about 500 nm, a type Ia isotherm typical of rigid MOFs is observed, while above approximately 1000 nm a pronounced gating behaviour is detected, starting at p/p = 0.2. With increasing crystal size this transition gate becomes steeper indicating a more uniform distribution of activation energies within the crystal ensemble. At an intermediate size (500-1000 nm), the DUT-8(Ni) crystals close during activation but cannot be reopened by nitrogen at 77 K possibly indicating monodomain switching.

Shaping of Flexible Metal‐Organic Frameworks: Combining Macroscopic Stability and Framework Flexibility

“…Rather than attributing this to the shaping of the powder, we expect that the polydispersity of the crystal size of the synthesized MIL‐53 powder is responsible for this observation. Previous reports on a variety of flexible MOFs involving MIL‐53(Al)‐NH 2 , [Cu 2 (bdc) 2 (npy) n ] MOF (bdc = terephthalate, bpy = 4,4‐bypyridine), DUT‐8(Ni),, and ZIF‐8 clearly demonstrated the correlation between crystal size and structural transition pressure. Larger crystals undergo the transformation more easily (for example at lower gate opening pressure) than smaller particles.…”

The impact of crystal size and temperature on the adsorption-induced flexibility of the Zr-based metal-organic framework DUT-98

“…Reports on MIL-53 indicate an impact of crystal morphology and size on the structural contraction upon solvent removal 15,16 . In a recent report, we demonstrated the suppression of adsorption-induced contraction in DUT-49 (DUT-Dresden University of Technology) upon downsizing of the crystals below 1 µm 9 and loss of flexibility upon downsizing of DUT-8 crystals 17,18 . In a similar fashion suppression of gate opening in ZIF-8 upon crystal downsizing was reported [10][11][12][13] and Kitagawa and co-worker reported on a shape-memory effect of gate opening transitions upon crystal downsizing in a pillared-layer MOF.…”

Structural‐Deformation‐Energy‐Modulation Strategy in a Soft Porous Coordination Polymer with an Interpenetrated Framework

“…[1] Numerous studies on engineering the structural flexibility of PCPs have been conducted with the aid of several methods involved framework design, [2] ligand modification, [3] guest-occupancy control, [4] and crystal downsizing. [5] Nonetheless, until recently, the focus has been on investigating the structural flexibility by utilizing crystallo-graphic diffraction and sorption profiles, and few reports on material design from energy perspectives are available. [6] To date, the energy landscapes of guest adsorption in robust materials have been thoroughly evaluated; [7] however, the energy landscapes of soft porous materials remain unexplored due to their complex structural behavior.…”