In aviation environments, particularly under emergency conditions such as fuel leakage, fire incidents, and cabin air contamination, exposure to toxic gases poses a serious risk to respiratory safety. In this study, metal–organic framework (MOF)–modified activated carbon was investigated as an advanced adsorbent to enhance the performance of respiratory filtration systems for aviation applications. The base activated carbon was produced from walnut shell–derived biochar and employed as the adsorption substrate. To improve surface properties and adsorption capacity, the activated carbon was modified via a hydrothermal method using four different MOFs, namely ZIF‑8, ZIF‑67, UiO‑66, and MIL‑101(Cr).The synthesized composites were characterized by X‑ray diffraction (XRD), Brunauer–Emmett–Teller (BET) surface area analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) to evaluate their crystalline structure, surface area, functional groups, and surface morphology. The results demonstrated that MOF modification significantly increased the specific surface area (up to approximately 1320 m²/g) and improved pore size distribution. Among the samples, MIL‑101(Cr)@AC exhibited the highest CO₂ adsorption capacity, while the UiO‑66/MIL‑101(Cr) composite showed superior stability under humid and ambient temperature conditions. The adsorption heat values were found to be in the range of 39–44 kJ/mol, indicating that physical adsorption was the dominant mechanism, which is favorable for cyclic operation.Overall, the findings suggest that MOF‑modified activated carbon represents an effective and practical approach for the design of high‑performance respiratory filters aimed at toxic gas removal in aviation and aerospace safety systems.