Controlling Thermal Expansion: A Metal–Organic\nFrameworks Route

Abstract

Controlling\nthermal expansion is an important, not yet resolved,\nand challenging problem in materials research. A conceptual design\nis introduced here, for the first time, for the use of metal–organic\nframeworks (MOFs) as platforms for controlling thermal expansion devices\nthat can operate in the negative, zero, and positive expansion regimes.\nA detailed computer simulation study, based on molecular dynamics,\nis presented to support the targeted application. MOF-5 has been selected\nas model material, along with three molecules of similar size and\nknown differences in terms of the nature of host–guest interactions.\nIt has been shown that adsorbate molecules can control, in a colligative\nway, the thermal expansion of the solid, so that changing the adsorbate\nmolecules induces the solid to display positive, zero, or negative\nthermal expansion. We analyze in depth the distortion mechanisms,\nbeyond the ligand metal junction, to cover the ligand distortions,\nand the energetic and entropic effect on the thermo-structural behavior.\nWe provide an unprecedented atomistic insight on the effect of adsorbates\non the thermal expansion of MOFs as a basic tool toward controlling\nthe thermal expansion.