In this multiscale computational screening study, we aimed to address the question: to what extent will the ranking of porous materials, and the selection of top performers identified in process modelling, depend on the choice of molecular forcefield? To do so, we generated distributions of CO2 and N2 adsorption isotherms in 690 MOFs using different forcefields (FFs) which represent the modelling choices commonly encountered in highthroughput computational screenings (HTCS) of materials for CO2 capture. We then conducted a systematic uncertainty quantification study using PSA process-level modelling to determine one's ability to identify top-performing candidate materials consistently across different FF definitions.