Evaluating Isoreticular Series of CALF-20 for Biogas Upgrading using a Pressure/Vacuum Swing Adsorption (PVSA) Process

Cyclic swing adsorption processes, such as pressure vacuum swing adsorption (PVSA), have emerged as a promising technology for upgrading biogas by separating carbon dioxide (CO2) from methane (CH4). The rational design of adsorbent materials with tailored properties is important for deployment of high-performance PVSA technology. Metal-organic frameworks (MOFs), particularly the CALF-20 isoreticular series, have attracted interest due to their high CO2 selectivity, thermal and water stability. In this study, we report a multiscale assessment of CALF-20 and its isoreticular five derivatives by integrating molecular simulations and PVSA cycle optimization. Structural parameters such as pore volume, pore size, and isosteric adsorption enthalpy were first calculated, followed by atomistic grand canonical Monte Carlo (GCMC) simulations. Process-level performances of the six materials were evaluated and optimized using the Thompson Sampling Efficient Multi-objective Optimization (TSEMO) algorithm. From the process-level optimization, we found that FumCALF-20 is the only material that can reach CH4 purity > 0.90 while maintaining high recovery. Other materials either lacked sufficient CO2 capacity or showed inefficient CH4 desorption at low pressures. This study underscores the value of process-level optimization in MOF evaluation and screening for energy-efficient biogas upgrading.