Development of a General Evaluation Metric for Rapid Screening of Adsorbent Materials for Postcombustion CO₂ Capture

Molecular simulations are combined with macroscopic pressure swing adsorption (PSA) modeling and process optimization to screen 2900 metal-organic frameworks (MOFs) for their suitability in separating CO₂ from N₂ under conditions of interest in postcombustion CO₂ capture. The hierarchical screening process eliminates MOFs based on metal price, new heuristics based on the internal energy of adsorption, full PSA modeling and optimization, and other factors. Based on PSA modeling of 190 materials, a general evaluation metric (GEM) is developed that can approximately rank the performance of adsorbent materials as defined by the lowest cost for postcombustion CO₂ capture. The metric requires only isotherm data and the N₂ internal energy of adsorption. The N₂ working capacity is the most important component of the metric, followed by the CO₂ working capacity, the CO₂/N₂ selectivity at desorption conditions, and the N₂ internal energy of adsorption. Additional analysis shows that the correlation between the cost of CO₂ capture and the GEM is better than that of other existing evaluation metrics reported in the literature. For the most promising MOFs, the cost to capture a tonne of CO₂ is estimated to be $30-$40 plus the cost of compressing the CO₂ product.