Structure-defined molecular heat transport in a two-dimensional conjugated metal–organic framework

Abstract

Understanding thermal transport in two-dimensional metal–organic frameworks (2D MOFs) is of both fundamental and technological importance. Although coordination chemistry and framework architecture offer powerful parameters for tuning heat transport, experimental studies of thermal transport in 2D MOFs remain scarce. Here, we investigate thermal transport in structure-defined 2D MOFs to establish structure–property relationships linking coordination chemistry and framework architecture to heat transport. As a model system, Co–BHT (Co = cobalt, BHT = benzenehexathiolate) thin films are studied. Thickness-dependent measurements using frequency-domain thermoreflectance quantify the thermal conductivity of Co–BHT thin films grown by modified chemical vapor deposition on Si/SiO2 substrates. Using a gold transducer layer, we determine the total thermal interfacial resistance, which includes contributions from the Au/Co–BHT, Co–BHT/SiO2, and SiO2/Si interfaces. The cross-plane thermal conductivity of Co–BHT thin films is determined to be ∼0.26 W m−1 K−1. The films exhibit a nearly isotropic structure without preferred crystal orientation, indicating that the measured cross-plane thermal conductivity reflects isotropic heat transport. The measured thickness-independent total thermal resistance of 4.25 × 10−7 m2 K W−1 arises from combined interfacial resistances and intrinsic resistances of the Au and SiO2 layers, together with thermal spreading in the Si substrate. These results provide quantitative insight into thermal transport in 2D MOFs.