Within the field of porous materials metal-organic frameworks (MOFs) rank among the most porous yet versatile compounds. This is due to their unique modular construction based on organic linkers and inorganic metal nodes and the effect of the often particularly large inner surface making them highly advanced adsorbents. Gas adsorption in MOFs can be accompanied by unique and often counterintuitive structural changes within the porous framework due to a complex interplay of inter-and intramolecular interactions of both, the adsorbate as well as the adsorbent. This flexibility also sets them apart from other classes of porous materials such as porous carbons or zeolites and lead to a variety of analytic methods providing deep insights in the underlying mechanisms on a molecular scale. Besides these molecular level construction and interactions, crystal size has shown to have an impact on the adsorption behaviour of MOFs as well. In many cases, the decrease in crystal size and thereby the decreased ratio of inner surface compared to the crystals outer surface leads to a stabilization of a metastable open pore phase due to a lack of nucleation sites required for the phase transition. This influences the thermodynamics and kinetics of the physisorption process and the possibly underlying flexible transitions. Various groups have found that smaller crystal size in ZIF-8 increases the gate opening penalty and therefore overall decreases the flexibility of this system. On the other hand larger crystals oftentimes show more internal strain due to a larger number of differently oriented domains within the crystal. This is also reflected by computational studies which suggest that the flexible breathing transition of MIL-53(Al) can occur via a layer-by-layer mechanism as well as one involving multiple discrete nucleation points, depending also on external pressure. This leads to altered kinetics of the phase transition as in MIL-53(Al) a slower breathing transition with increasing crystal size but also a lack of a phase transition in submicron sized crystals can be observed. The altered kinetics that come with changes in crystal size have e.g. been utilized to boost the dynamic separation of ethylene and ethane by increasing the crystal size of a ZnAtzPO4 framework. In general, crystal size and morphology needs to be acknowledged as a factor that can influence the physical properties of MOF materials but can also be a tool to design new MOF materials for specific applications. While adsorbing and desorbing gas molecules, MOFs are exposed to an adsorption/desorption stress, which may cause reversible or irreversible framework deformation and may lead to changing its crystallites surface texture, causing breaks or defects, replacing solvent molecules from the synthesis or accumulates in the pore after repeated exposure. This is often accompanied by an decrease in crystal size due to fracture of larger crystals until a certain finite value is reached, an increase in gate opening pressure and a less steep opening slope, decrease in gate closing pressure and a smaller total pore volume. These structural changes can be at least partially understood as a materials response to an adsorption-induced stress exerted from a fluid adsorbate onto its solid surface. Such phenomenon can be termed "adsorption milling". Adsorption stress is also observed in other porous materials such as porous carbons. Gor and Neimark modelled the adsorption-induced deformations in the mesoporous silica using Derjaguin-Broekhoff-de Boer theory for capillary condensation and Quenched Solid Density Functional Theory indicating advantages and disadvantages of each for them for materials with particular pore size. Coudert and Neimark developed the stress-based model for breathing crystalline porous solids. In terms of experimental methodology, the mechanical stress is often evaluated by mercury intrusion , in situ high-pressure Powder X-ray Diffraction (PXRD) experiments or in silico prediction . However, these techniques have certain limitations e.g. in case of rigid mesoporous frameworks, which are often quite sensitive to ambient conditions, irreversible transitions are observed at relatively low pressures. In such cases, more precise and sensitive technique should be developed. g -1 . A characteristic feature of this material is the utilization of a carbazole based cuboctahedral 12-conneting metal-organic polyhedron (MOP) also present in other DUT materials acting as a well-defined building block for the construction of MOFs with high porosity and a high concentration of open metal sites. Additional open metal sites are introduced by using of tritopic linker H3CBCDC (9-(4'-carboxy-[1,1'-biphenyl]-4-yl)-9H-carbazole-3,6-dicarboxylic acid) in the construction of the framework, in which carboxylate groups at the biphenyl moiety form an additional copper(II) paddle-wheel connecting four MOPs yielding a (4,12)-connected network with a four, twelve connected (ftw) topology (see Figure ). Previously we found DUT-76(Cu) to have an exceptional capacity for high-pressure ethylene storage at 298 K.