Bottom-Up Computational Design of Shape-Selective Organic Macrocycles for Humid CO2 Capture

The capture of carbon dioxide (CO2) emissions using porous solids is challenging because polarized water molecules bind more strongly in most materials than non-polarized CO2 molecules. This is a challenge for both flue gas capture and for direct air capture alike. We developed a bottom-up computational screening workflow to calculate the binding energy of 27,446 diverse molecular fragments with both CO2 and water. Most molecules favoured water binding, but bent, ‘clip’-like aromatic molecules showed potential for the desired reverse selectivity. This suggested that aromatic macrocycles with specific shapes might promote multiple weak p-p interactions with CO2 that could surpass stronger but less numerous dipole-p interactions with water. We synthesized two water- and acid-stable molecular prisms with triangular and square geometries, as suggested by computation. Experiments confirmed that the CO2 capture capacity of these prisms is unaffected by high relative humidity, surpassing the performance of benchmark commercial porous materials.