Densification-driven power factor enhancement in 2D MOF composites for waste heat recovery across broad temperature ranges

Abstract

Metal–organic frameworks (MOFs) show significant promise for thermoelectric applications due to their intrinsically low thermal conductivities. However, their practical utility remains limited by their poor electrical conductivity and suboptimal power factors. In this work, high power factors up to 140 μW m⁻¹ K⁻² were obtained through in situ synthesis of MOF-carbon nanotube (CNT) composites followed by cold compression, which were about 1000 times higher than those of the initial MOFs and superior to the values of MOF-based thermoelectric materials reported in literature. The compression concurrently enhanced the figure of merit (ZT) by 1.5 times. The resulting freestanding films exhibited exceptional flexibility and operational stability from cryogenic (98 K) to elevated temperatures. A flexible thermoelectric generator prototype demonstrated its practical viability with an areal power density of 26 W m⁻² at ΔT = 180 K. This strategy establishes a pathway toward high-performance, low-temperature-tolerant MOF thermoelectrics for flexible energy harvesting under a wide temperature range.