Cold Sintering Enables Incorporation of ZIF‐8 into PbTe Composites for Mid‐Temperature Thermoelectric Energy Conversion

ABSTRACT

Metal–organic frameworks (MOFs) are promising candidates for constructing thermoelectric composites with low lattice thermal conductivity, thanks to their inherent porous structure and controllable particle size. However, their inferior thermal stability confines MOFs to low‐temperature sintered thermoelectric systems. In this work, ZIF‐8 nanoparticles were incorporated into n‐type mid‐temperature PbTe _0.99 I _0.01 via cold sintering (CSP). Relative to spark plasma sintering, low‐temperature CSP well preserves the porous structure of ZIF‐8, while inducing fine grains, nanoscale Pb precipitates and dense dislocations. These multiscale defects strongly scatter mid‐ and low‐frequency phonons, reducing lattice thermal conductivity to 0.67 W·m ^{− 1} ·K ^{− 1} at 650 K. As an electron acceptor, ZIF‐8 also drives interfacial charge transfer and band bending to filter low‐energy carriers, elevating the Seebeck coefficient and thermoelectric quality factor. The composite delivers a peak zT of 1.40 and an average zT of 1.01 at 650 K. The assembled thermoelectric module achieves a high conversion efficiency of 6.5% under a 427 K temperature gradient. This study broadens the application of MOFs to high‐efficiency mid‐temperature thermoelectric energy conversion.