Synthesis and DFT study of NH2-MOF235(Fe)-derived ZnFe2O4–Fe2O3–ZnO multiple heterojunction nanocomposites for triethylamine gas detection

Abstract

Metal oxide semiconductor (MOS)-based gas sensing materials are highly suitable for gas sensor development due to their exceptional physicochemical properties. Enhancing performance through metal–organic framework (MOF) derivatization and heterojunction construction has emerged as a promising strategy. In this study, NH₂-MOF235(Fe) was first synthesized as a precursor for the growth of MOF-5 on a MOF framework, leading to the successful fabrication of ZnFe₂O₄–Fe₂O₃–ZnO multi-heterostructure nanocomposites derived from NH₂-MOF235(Fe)@MOF5 MOF-on-MOF via a precisely controlled stepwise solvothermal method. Gas-sensitivity evaluations revealed that the ZZF4 sensor exhibited outstanding TEA sensing performance, achieving a response value of 44.9 to 50 ppm TEA, which is 10.3 times higher than that of the F1 sample. The sensor demonstrated a rapid response time of 1 second and a low detection limit of 0.5 ppm. Comprehensive characterization through XPS, UV-vis, PL, and Raman spectroscopy attributed the superior performance to the tunable electronic structure of ZnFe₂O₄–Fe₂O₃–ZnO heterojunctions and optimized interfacial reactions, including enhanced surface adsorption sites, interfacial charge transport, and adsorption energy. First-principles calculation performed with VASP further validated the role of electronic structure modulation and heterogeneous interface optimization in improving gas-sensing properties. Additionally, this study elucidated the TEA sensing mechanism and performance variations among heterostructure materials with different compositions. These findings offer a robust strategy for the synthesis of MOF-on-MOF-derived multi-heterojunction nanocomposites and provide a pathway for advancing electronic structure engineering and interfacial optimization in gas-sensing applications.