Quantum Buckling in Metal-Organic Framework Materials.

R Matthias Geilhufe

doi:10.1021/acs.nanolett.1c03579

Abstract

Metal–organic frameworks are porous materials composed of metal ions or clusters coordinated by organic molecules. As a response to applied uniaxial pressure, molecules with a straight shape in the framework start to buckle. At sufficiently low temperatures, this buckling has a quantum nature described by a superposition of degenerate buckling states. Buckling states of adjacent molecules couple in a transverse field Ising type behavior. Based on the example of the metal organic framework topology MOF-5, we derived the phase diagram under applied strain, showing a normal phase, a parabuckling phase, and a ferrobuckling phase. At zero temperature, quantum phase transitions between the three phases can be induced by strain. This novel type of order opens a new path toward strain induced quantum phases.

Highlights

Metal−organic frameworks are porous materials composed of metal ions or clusters coordinated by organic molecules
Metal−organic framework materials are compounds built of metal ions or clusters coordinated by organic ligands
After the first MOFs were realized in the late 1990s,5 more than 90 000 stable structures have been synthesized and characterized to date.[6]. They have been intensively discussed in the context of gas sorption and storage, catalysis, electronic devices, etc.[7−9] Mechanical properties and the flexibility of MOFs are summarized in ref 10

Summary

Introduction

Metal−organic frameworks are porous materials composed of metal ions or clusters coordinated by organic molecules. The present paper shows how uniaxial pressure in MOFs can be used to induce the quantum buckling of ligand molecules. MOF-5 is extremely soft, with a bulk modulus of 15.37 GPa.[11] Applying strain along one of the Cartesian axes, the bond lengths within the Zn4O clusters and BDC molecules are squeezed up to the point where the structure responds by a buckling of the molecules.

Results

Conclusion