Linker Rotational Dynamics as a Hidden Dimension to Suppress and Tailor Heat Transport in Flexible Metal-Organic Frameworks.

Abstract

Tuning thermal conductivity (κ) of metal-organic frameworks (MOFs) is pivotal for advancing their emerging thermoelectric applications and addressing the heat dissipation bottleneck in gas adsorption processes, yet heat conduction mechanisms in MOFs, particularly from the perspective of intrinsic lattice vibrations, remain elusive, limiting rational thermal engineering. Here, we focus on organic ligand rotational dynamics and elucidate their critical but long-overlooked modulations on thermal transport. Through elaborate atomistic simulations on prototypical MIL-47, we report that low-frequency, anharmonic linker librations dramatically intensify phonon scattering, inducing an over 2-fold reduction in κ. Such a suppression effect is further confirmed to be universal across diverse flexible frameworks featuring rotatable ligands, including the known zeolitic imidazolate and covalent organic families. Accordingly, we evaluate multiple practical strategies to regulate κ by tailoring linker rotational dynamics. These insights open vast avenues for the flexible design of MOFs' thermal performance to meet their energy-related applications.