Effective carbon dioxide adsorption in graphene oxide–piperazine-modified Ni-MOF-74 frameworks

BACKGROUND: The rising atmospheric CO₂ concentration, driven primarily by industrial emissions, has heightened the need for advanced carbon capture materials. Metal–organic frameworks (MOFs), particularly Ni-MOF-74, offer high CO₂ adsorption potential but suffer from structural fragility and limited performance under ambient conditions. To address these limitations, a GO@Ni-MOF-74/PZ composite was synthesized via a solvothermal method, incorporating graphene oxide (GO) to improve structural stability and piperazine (PZ) as a nitrogen-rich functional agent to enhance CO₂ affinity. RESULTS: Comprehensive characterization using various techniques confirmed the successful integration of GO and PZ without compromising MOF crystallinity, while significantly increasing surface area and micropore volume. The CO₂ adsorption capacity improved from 4.5 mmol g⁻¹ for pristine Ni-MOF-74 to 5.2 mmol g⁻¹ for GO@Ni-MOF-74/PZ at 1 bar and 25 °C. Grand canonical Monte Carlo simulations showed good agreement with experimental adsorption trends and relative uptake behavior, providing molecular-level insights into the adsorption mechanism. Adsorption data were further analyzed using Langmuir, Freundlich and Sips isotherm models, enabling quantitative evaluation of site affinity, surface heterogeneity and maximum uptake capacity. CONCLUSION: These results demonstrate that GO-functionalized Ni-MOF-74 combined with amine-based modification offers a promising pathway toward efficient and scalable CO₂ capture technologies.