A search for selectivity to enable CO2 capture with porous adsorbents

Abstract

Fundamental aspects and actual developments of selective CO₂ capture from relevant sources (flue gas or air) by reversible physisorption are critically reviewed. Thermodynamic as well as kinetic principles of CO₂ adsorption in the presence of other gases are linked to current approaches of materials development. Whilst hundreds or even thousands of porous materials have been evaluated for CO₂ capture, research in this field is still full of challenges, as for instance a feasible physical adsorbent for CO₂ capture for direct capture from air has still not been found. Current attempts towards the optimization of materials in terms of CO₂ uptake/selectivity, regenerability, tolerance against water, and cost most often exclude each other. The aim of this article is not to summarize all recent attempts towards tailoring of materials for selective CO₂ capture but to discuss the most fundamental aspects of adsorptive CO₂ separation in order to illuminate the “sweet spot” to be explored when electronic structure, polarity, and pore size/geometry are rationally balanced and optimized – just like nature does when exerting selective binding of gases.