Unveiling Thermoelectric Properties of SURMOF Nanofilms: A New Frontier in Molecular Thermoelectrics

Abstract

Molecular thermoelectric materials, which harness molecular-level design principles to optimize energy conversion, have emerged as a promising strategy for addressing the limitations of bulk inorganic thermoelectrics, such as brittleness and high production costs. In this study, a layer-by-layer (LbL) engineered HKUST-1 surface-mounted metal-organic framework (SURMOF) nanofilm is proposed as a promising thermoelectric nanostructure, systematically characterized across its thickness. By employing LbL growth of HKUST-1 on self-assembled monolayers (SCnCOOH, n = 2, 10), nanofilms ranging from 5 to 30 nm in thickness are successfully fabricated. Thermoelectric characterization of these nanofilms revealed a significant enhancement in Seebeck coefficient (S) and power factor (PF), with PF values surpassing those of conventional organic SAMs by a factor of 103. Ultraviolet photoelectron spectroscopy (UPS) measurements further confirmed a correlation between molecular orbital alignment and thermoelectric performance, particularly in junctions doped with guest molecules such as ferrocene (Fc) and 7,7,8,8-tetracyanoquinodimethane (TCNQ). These findings establish SURMOF nanofilms as a viable molecular thermoelectric architecture, offering enhanced carrier transport, guest-responsive electronic properties, and precise structural control at the nanoscale.