This study explores the simultaneous extraction of methane (CH4) from natural gas hydrates (NGH) in permafrost and marine environments, coupled with the sequestration of carbon dioxide (CO2) as hydrates. This dual approach aims to achieve sustainable energy recovery and greenhouse gas reduction. Molecular Dynamics simulations were conducted to analyze the influence of temperature (270–285 K), pressure (6–12 MPa), and initial CH4 hydrate saturation (75 %–100 %) on CH4-CO2 gas replacement characteristics. These thermodynamic ranges were selected based on the CH4 and CO2 hydrate phase equilibrium diagram. Findings reveal a strong temperature dependence in the replacement process, with enhanced CH4 recovery by 15 % at higher temperatures but decreased CO2 storage capacity by 3 %, indicating a trade-off between energy extraction and sequestration efficiency. In contrast, pressure effects at constant temperature are minimal. High initial hydrate saturations improve CH4 recovery but reduce CO2 sequestration efficiency due to limited molecular mobility within the hydrate structure, resulting in higher CH4/CO2 replacement ratios varying from 1.4 to 2.6. Additionally, the study examines the mechanical properties, including Young's modulus and fracture strength, of CH4-CO2 hydrates post-replacement at 280 K and 8 MPa. The study offers valuable perceptions into CH4 recovery using CO2 gas and explores the mechanical behaviour of mixed hydrates. These insights are pivotal for advancing sustainable energy extraction and environmental protection strategies, particularly in utilizing gas hydrates as a resource while mitigating climatic impacts.