Peptide metal–organic frameworks under pressure: flexible linkers for cooperative compression

Abstract

We investigate the structural response of a dense peptide metal-organic framework using in situ powder and single-crystal X-ray diffraction under high-pressures. Crystals of Zn(GlyTyr) show a reversible compression by 13% in volume at 4 GPa that is facilitated by the ability of the peptidic linker to act as a flexible string for a cooperative response of the structure to strain. This structural transformation is controlled by changes to the conformation of the peptide, which enables a bond rearrangement in the coordination sphere of the metal and changes to the strength and directionality of the supramolecular interactions specific to the side chain groups in the dipeptide sequence. Compared to other structural transformations in Zn(ii) peptide MOFs, this behaviour is not affected by host/guest interactions and relies exclusively on the conformational flexibility of the peptide and its side chain chemistry.

Flat Phonon Band-Based Mechanism of Amorphization of MOF-5 at Ultra-low Pressures

“…30 Similar crystalline−crystalline transformation has been reported in peptide MOFs, Zn-(GlyTyr) 2 on compression, driven by bond rearrangements of Zn(II) centers, and accompanied by changes in strength and directionality of H-bonds. 33 While crystallanity of MOF-5 is maintained for very low strains (|ϵ h | < 0.015), at larger hydrostatic strains, distorted configurations on energy-optimization exhibit a higher degree of structural disorder (see Figure 3b,c,d). Loss of long-range order on compression is evidenced by significant reduction in strain energies and stresses due to internal structural rearrangements in (2 × 2 × 2) and (3 × 3 × 3) strained supercells, compared to that in the corresponding (1 × 1 × 1) cells (see Figure 2b,c), elucidating the crystal-to-amorphous transition in MOF-5.…”

“…This disruption in crystal-topology originating from order-to-disorder transition is quite distinct from displacive disorder or pressure-induced amorphization driven by soft, yet stable flat phonons . Similar crystalline–crystalline transformation has been reported in peptide MOFs, Zn­(GlyTyr) 2 on compression, driven by bond rearrangements of Zn­(II) centers, and accompanied by changes in strength and directionality of H-bonds …”

Pressure-Induced Hexagonal to Monoclinic Phase Transition of Partially Hydrated CePO4

“…Indeed, this phenomenon and even the absorption of alcohol in the porous of R-CePO 4 due to compression is not a nai ̈ve hypothesis and has been observed in other oxides with large empty cavities. 53 The exploration of this hypothesis will require the performance of experiments with dehydrated R-CePO 4 immersed under a selection of pressure media with molecules of different size, 54 which is beyond the scope of the present work.…”

Self-healing ferroelastic metal–organic framework sensing guests, pressure and chemical environment

“…[19][20][21][22][23] Owing to their internal structure, MOFs are highly elastic and pressure-sensitive. [24][25][26][27][28][29] These features can be further increased by flexible linkers and large voids. Pressure is a thermodynamic variable that affects the volume of crystals more efficiently than it is done by temperature.…”