Probing the capability of the MOF-74(Ni)@GrO composite for CO2 adsorption and CO2/N2 separation: A combination of experimental and molecular dynamic simulation studies

Given the significant impact of carbon dioxide emissions on current and future human life, the imperative for CO2 reduction becomes evident. Metal-organic frameworks (MOFs) composites stand out as highly effective adsorbents for CO2 capture and separation. In this study, MOF-74(Ni)@graphene oxide (GrO) composites were successfully generated through a hydrothermal synthesis route. The thermal, pore, and textural properties of the new MOF composites were experimentally tested through TGA, N2 adsorption-desorption, XRD, and FTIR. The adsorption and separation characteristics of the new MOF composites were evaluated through experimental and molecular dynamic (MD) simulation studies at ambient conditions. Interestingly, the BET surface area of all composites significantly increased compared to the pristine MOF. Among all composites, MOF-74(Ni)@GrO-10 demonstrated the highest value, surpassing others by 1060 cm2/g. MOF-74(Ni)@GrO-10 composite demonstrates the maximum amount of CO2 uptake capacity of 5.76 mmol/g experimentally and 6.65 mmol/g numerically, evidencing a substantial enhancement of 25 % and 28 % in comparison to the pristine MOF-74(Ni). The determination of CO2/N2 selectivity for all samples was carried out through a single-component isotherm under post-combustion conditions (PCO2/PN2: 0.15 bar/ 0.75 bar). Concerning CO2/N2 selectivity, the MOF-74(Ni) @GrO-10 composite also displayed the highest selective adsorption values of 44 and 45 experimentally and numerically, respectively. This marks a significant 7 % enhancement compared with the bare MOF. MOF-74(Ni) @GrO-10 exhibited a significantly higher heat of CO2 adsorption compared to bare MOF-74. As evidenced by both experimental and numerical results, MOF-74(Ni)@GrO-10 indicated 37 kJ/mol and 39 kJ/mol, and MOF-74 (Ni) showed 34.5 kJ/mol and 36.5 kJ/mol heat of CO2 adsorption, implying that CO2 molecules have a stronger interaction with the composite adsorbent than the bare MOF. MOF-74(Ni)@GrO-10 also exhibited high stability, preserving 95 % of its structure after five consecutive adsorption-desorption cycles in both studies. The research finding implies that MOF-74(Ni)@GrO-10 is a promising adsorbent that can be widely used in adsorption and separation technology.