Metal‐Organic Framework‐Derived Metastable Cu2ZnSnS4/ZnS Heterojunction Realizes Kinetic‐Controlled Lattice Strain Engineering and Built‐In Electric Field Synergistically Enhanced Microwave Absorption

Collaborative optimization of dielectric loss, impedance matching, and effective absorption bandwidth (EAB) in sulfide‐based microwave absorbers remains challenging. In particular, the coupled role of lattice strain and built‐in electric field (BIEF) in governing polarization relaxation and microwave attenuation is poorly understood. Herein, we propose a kinetically controlled lattice strain engineering strategy based on Metal‐Organic Framework (MOF)‐derived metastable Cu 2 ZnSnS 4 (CZTS)/ZnS heterojunctions. Using bimetallic Zn/Cu‐MOFs as precursors, heterojunction materials are synthesized via controlled sulfurization and pyrolysis, enabling systematic regulation of phase composition, morphology, defect concentration, and electromagnetic properties. The optimal sample (CZSS‐700) achieves a minimum reflection loss (RL min ) of −46.7 dB at a matching thickness of only 1.5 mm. The enhanced absorption performance is attributed to the combined effects of the CZTS/ZnS heterojunction interface, sulfurization‐induced lattice strain, and defect‐induced polarization loss, together with improved impedance matching. This work clarifies the polarization relaxation enhancement mechanism associated with sulfurization‐induced lattice strain and BIEF coupling, and provides an experimental and theoretical basis for the design of high‐performance MOF‐derived sulfide‐based microwave absorbers.