Novel bimetallic ZIF (Cu-Zn-ZIF-8) for enhanced and stable carbon capture from industrial moisture-laden flue gas through systematic and hierarchical material and process optimization

Post-combustion carbon capture (PCCC) in the presence of moisture faces challenges due to competition between CO 2 and H 2 O for adsorption sites, thereby impacting both efficiency and stability. Ten adsorbents, including metal–organic frameworks and bimetallic ZIFs, were investigated using simulated flue gas conditions: 12 vol% CO 2 , 10 vol% H 2 O, 8 vol% O 2 , and the balance N 2 . Cu-Zn-ZIF-8 demonstrated good performance among the evaluated adsorbents and was selected for further work. The adsorption process was optimized using a Central Composite Design (RSM-CCD) and an Artificial Neural Network (ANN) model to confirm the results. An increase in CO 2 uptake to 5.6 mmol/g was observed under optimal conditions, viz., 40 °C, 5 g of Cu-Zn-ZIF-8, flow rate of 150 ml/min, and carbonation time of 220 min. Integration of Cu 2+ into the ZIF-8 framework was evidenced by Cu 2p XPS and corroborated by XRD, which showed preservation of the parent ZIF-8 framework. The Cu-Zn-ZIF-8 showed a BET surface area of 974 m 2 /g and a pore volume of 0.47 cm 3 /g. The Elovich model provided an accurate fit to the adsorption kinetics, and the Langmuir isotherm accurately fit the experimental data. A preliminary techno-economic analysis determined that the adsorbent lifetime is the key factor affecting the overall CO 2 capture cost. Even under humid conditions, the adsorbent retained 80.4% of its adsorption capacity after 10 cycles, confirming its good stability.