Densification-driven power factor enhancement in Cu-MOF hybridization carbon nanotube composites for waste heat recovery across broad temperature ranges

Abstract

Metal-organic frameworks (MOFs) show significant promise for thermoelectric applications. However, the practical adoption of MOFs is impeded by poor electrical conductivity and low power factors. Constructing composites is a widely exploited strategy to advance MOFs performance by leveraging synergistic effects to improve electronic transport and achieve superior thermoelectric properties. In this work, we fabricated freestanding films of Cu-based nanowires MOF hybrid incorporated with carbon nanotubes via a one step, self-templated and catalyst-free in-situ synthesis followed through cold pressing. By adjusting the concentration of carbon nanotubes and the pressing time, the composites achieve a power factor of up to 630 μW•m -1 •K -2 , which is approximately 2 times higher than that highest reported values for the initial copper-based and MOF-based thermoelectric materials in literature. A prototype flexible thermoelectric generator achieved a practical power density of 69.6 W•m -2 under a temperature difference of 180 K. The pressed freestanding films exhibit exceptional flexibility and operational stability over a broad temperature range, from cryogenic (98 K) to elevated temperatures. This strategy yields high thermoelectric performance with simpler, nontoxic nanowire chemistries, enabling flexible thermoelectric generator that operate efficiently across a broad temperature range, including cryogenic conditions.