Enhanced elastic stability of a topologically disordered crystalline metal--organic framework

TL;DR

This study demonstrates that aperiodic topology in a metal-organic framework enhances its elastic stability, offering a novel approach to improve mechanical resilience without increasing density or reducing porosity.

Contribution

It introduces a new design paradigm where aperiodic network topology, rather than increased connectivity, enhances elastic stability in MOFs.

Findings

Aperiodic TRUMOF-1 resists pressure-induced collapse better than ordered MOF-5.

Topology influences elastic stability, with aperiodicity preventing cooperative failure.

Aperiodicity can be a general design principle for mechanically robust frameworks.

Abstract

By virtue of their open network structures and low densities, metal--organic frameworks (MOFs) are soft materials that exhibit elastic instabilities at low applied stresses. The conventional strategy for improving elastic stability is to increase the connectivity of the underlying MOF network, which necessarily increases material density and reduces porosity. Here we demonstrate an alternative paradigm, whereby elastic stability is enhanced in a MOF with an aperiodic network topology. We use a combination of variable-pressure single-crystal X-ray diffraction measurements and coarse-grained lattice-dynamical calculations to interrogate the high-pressure behaviour of the topologically aperiodic system TRUMOF-1, which we compare against that of its ordered congener MOF-5. We show that the topology of the former quenches the elastic instability responsible for pressure-induced framework collapse in the latter, much as irregularity in the shapes and sizes of stones acts to prevent cooperative mechanical failure in drystone walls. Our results establish aperiodicity as a counterintuitive design motif in engineering the mechanical properties of framework structures, relevant to MOFs and larger-scale architectures alike.