Role of particle size and surface functionalisation on the flexibility behaviour of switchable metal-organic framework DUT-8(Ni)

Flexible MOF nanoparticles, i.e. MOF nanoparticles that change their structure upon external stimuli such as guest uptake, are promising for numerous applications including advanced gas adsorption, drug delivery and sensory devices. However, the properties of MOFs are typically characterised based on the bulk material with no consideration of how the particle size and external surface influences their performance. This combined computational and experimental contribution investigates the influence of the particle size and surface functionalisation on the flexibility of DUT-8(Ni) (Ni2 (2,6-ndc)2 dabco, ndc = naphthalene dicarboxylate, dabco = 1,4-diazabicyclo[2.2.2]octane, DUT=Dresden University of Technology). DUT-8 nanoparticles remain rigid in their open pore form while microparticles, synthesised under slightly different conditions, undergo gate opening upon nitrogen adsorption suggesting that the particle size has an important role to play in the flexibility of DUT-8. While the adsorption environment at the surface capped with modulators smaller than the 2,6-ndc ligand is very different compared to the bulk of the crystal with considerably weaker guest-framework interaction, simulations reveal that the nanoparticles should close. We conclude that the size of the nanoparticles is not the major contributor for keeping DUT-8 nanoparticles open but that it is more likely that defects or nucleation barriers dominate. Moreover, our work reveals for the first time that functionalising the external surface of nanoparticles with different modulators or capping groups offers the opportunity to manipulate the gate opening / closing pressure. This principle is generally applicable and could be exploited to tune the gate openig / closing pressure for the application of interest

Flexibility in DUT-8(Cu) Metal–Organic Framework: Impact of Cluster, Stress, History, and Hierarchical Texture

The flexibility of metal–organic frameworks (MOFs) featuring stimuli-responsive structural transitions is often governed not only by the chemical composition and topology but also by orthogonal factors such as particle size, desolvation method, and history of the sample. A precise understanding of the mechanism behind such observations has been lacking up to now, and there are still substantial open questions concerning the impact of sample treatment history. The DUT-8(M) family ([M$_2$(2,6-ndc)2(dabco)]$_n$, 2,6-ndc = 2,6-naphthalene dicarboxylate, dabco = 1,4-diazabicyclo-[2.2.2]-octane), encompasses isostructural compounds based on Ni, Zn, Co, and Cu in the cluster node and is representative of pillared layer MOFs, often showing flexible behavior. In this contribution, we discuss a possible explanation for the differences in flexibility observed in desolvated phases of DUT-8(Cu). Theoretical calculations and crystallographic data shed light on the preferred formation of interpenetrated confined closed pore phases in DUT-8(Cu) in contrast to DUT-8(Ni, Co, Zn) where the closed pore phases are formed

Raman spectroscopy studies of the terahertz vibrational modes of a DUT-8 (Ni) metal-organic framework

Low-frequency lattice vibration modes have been discussed to play a crucial role in phase transformation process of switchable metal–organic frameworks (MOFs). Therefore, Raman spectroscopy was applied to study lattice dynamics of the pillared layer DUT-8(Ni) framework (DUT – Dresden University of Technology), existing in rigid and flexible form. The open pore phase and the close pore phase could be unanimously identified by breathing modes in the corresponding Raman character of low-frequency vibrations. The flexible version of DUT-8 could be distinguished by orientation dependent Raman spectroscopy experimen

Single particle Raman spectroscopy analysis of the metal-organic framework DUT-8(Ni) switching transition under hydrostatic pressure

Experimental in situ observations of phase coexistence in switchable metal-organic frameworks are reported to provide a fundamental understanding of dynamic adsorbents that can change their pore structure in response to external stimuli. A prototypical flexible pillared layer framework DUT-8(Ni) (DUT = Dresden University of Technology) was studied under hydrostatic pressure by in situ Raman spectroscopy on single crystals. The closing transition of the open pore phase (op) containing DMF in the pores in silicon oil as a pressure transmitting fluid, as well as the closed pore phase (cp) to op transition under pressure in methanol, were studied. Phase coexistences during both transitions were observed

Опис до патенту на корисну модель № 105963 "Вібраційно-відцентровий сепаратор"

Вібраційно-відцентровий сепаратор містить поміщений в кожух вібровідцентровий решітний барабан, над яким розміщений пристрій для завантаження, пневмосепаруючий пристрій з розкидачем, направляюча ділянка якого виконана у вигляді поверхні, утвореної обертанням навкруг вертикальної осі кривої найкоротшого спуску - брахістохрони. Розгінна ділянка розкидача виконана у вигляді ряду послідовно сполучених між собою зрізаних конусів, що обернені більшою основою вверх та утворюють ступінчасту поверхн