Pt decorated CoFe ₂O ₄/Co ₃O ₄ nanosheets derived from 2D Fe–Co MOF for enhanced HCHO detection

Highly sensitive and selective detection of volatile organic compounds (VOCs) is of great significance, and designing a suitable microstructure and constructing heterostructures are two main effective strategies for gas-sensing materials to achieve this goal. Herein, Pt nanoparticles decorated CoFe₂O₄/Co₃O₄ nanosheets were prepared by solution method for highly accurate detection of formaldehyde (HCHO), where the CoFe₂O₄/Co₃O₄ nanosheets were derived from two-dimensional Fe-Co metal-organic framework (MOF). The response (<em>R</em>_g/<em>R</em>_a) of ternary Pt₂/CoFe₂O₄/Co₃O₄ composite to 100 ppm HCHO at 280 °C can be calculated as 95.5, and it still exhibits a very high response to low concentration of HCHO (1.26 to 50 ppb HCHO gas) and an ultra-low limit of detection (LOD) of 6 ppb. The ternary composite also presents excellent reproducibility, selectivity and long-term stability. The first-principles calculations demonstrate that the Pt/CoFe₂O₄/Co₃O₄ model presents the most stable structure and the strongest adsorption capacity for HCHO. The high sensitivity of Pt/CoFe₂O₄/Co₃O₄ to HCHO can be mainly ascribed to the formation of multi-heterojunctions and the catalytic effect of Pt nanoparticles. This work provides a facile preparation of MOF-derived multi-heterojunction materials, and highlights superior gas-sensing performances to VOCs.