Pore Shape Modification of a Microporous Metal–Organic Framework Using High Pressure: Accessing a New Phase with Oversized Guest Molecules

Abstract

Pressures up to 0.8 GPa have been used to squeeze a range of sterically 'oversized' C5-C8 alkane guest molecules into the cavities of a small-pore Sc-based metal-organic framework. Guest inclusion causes a pronounced reorientation of the aromatic rings of one third of the terephthalate linkers, which act as 'torsion springs', resulting in a fully reversible change in the local pore structure. The study demonstrates how pressure-induced guest uptake can be used to investigate framework flexibility relevant to 'breathing' behavior and to understand the uptake of guest molecules in MOFs relevant to hydrocarbon separation.

Correlating Pressure‐Induced Emission Modulation with Linker Rotation in a Photoluminescent MOF

“…In addition, both of these effects appear to actually increase the pore volume, with an increase of 1105 Å 3 on increasing the pressure from ambient to 2.1 GPa (Table S2). This is similar to behaviour observed on increasing pressure in other MOFs, such as ZIF‐8, HKUST‐1, Sc 2 BDC 3 and ZAG‐based MOFs, where ligand flexibility facilitates significant pore volume and content changes, though the changes observed here are much smaller, and the mechanism (i.e. increase in population of a conformer that is less favourable under ambient conditions), is completely new.…”

Intrinsically porous molecular building blocks for metal organic frameworks tailored by the bridging effect of counter cations

“…6 Aside from the many attractive features of MOFs (e.g., huge surface area and low crystal density), construction of networks with tailored porosity and a prospective application have been the main highlight. [7][8][9] A major drawback to the success of the rational and predesigned synthesis of robust porous materials has been the limited access to the pores within open structures. 10 This is a critical aspect to the utility of these structures and occurs due to either self-interpenetration 11 as observed for very open frameworks or strong host-guest interactions that lead to the destruction of the host framework when removal or exchange of guests is attempted.…”

Flexibility in Metal–Organic Frameworks: A Basic Understanding

“…Until now, some pressure-induced behaviors of flexible MOFs have been investigated [94][95][96][97]. However, the number of MOFs that have been exposed to mechanical stress is trivial in comparison to the immense number of MOFs that have been produced [61].…”