Defect-dependent colossal negative thermal expansion in UiO-66(Hf) metal-organic framework

TL;DR

This study reports a metal-organic framework exhibiting the strongest negative thermal expansion, with defect engineering used to tune its thermal properties.

Contribution

It demonstrates defect-dependent tuning of negative thermal expansion in a MOF, a novel approach for controlling thermal behavior.

Findings

UiO-66(Hf) shows record negative thermal expansion.

Vacancy defects influence thermal densification and NTE magnitude.

Defect inclusion systematically tunes MOF thermal properties.

Abstract

Thermally-densified hafnium terephthalate UiO-66(Hf) is shown to exhibit the strongest isotropic negative thermal expansion (NTE) effect yet reported for a metal-organic framework (MOF). Incorporation of correlated vacancy defects within the framework affects both the extent of thermal densification and the magnitude of NTE observed in the densified product. We thus demonstrate that defect inclusion can be used to tune systematically the physical behaviour of a MOF.