CO2 capture enhancement in MOFs via the confinement of molecules

Metal–organic frameworks (MOFs) have become the most promising molecular sponges to capture gases contributing to the greenhouse effect, e.g. CO2, due to various desirable features such as tuneable pore shapes, sizes and functionalities, a great surface area, resistance to harsh conditions (wide ranges of pH, temperatures, humidity, etc.), ease of their preparation, and in most cases, a high degree of recovery. Thus, despite many MOFs adsorbing extensive amounts of CO2 in their pristine form, it has been demonstrated that their uptake capability can be considerably enhanced when they are post-synthetically modified by the confinement of molecules with different polarities, as a result of new physical–chemical interactions between the pre-confined species and the CO2 molecules within their cavities, for example, via the bottleneck effect, H-bonds and/or even π–π stacking interactions. Thus, this review covers selected studies, mainly from the last five years, highlighting the most significant advances on the CO2 enhanced uptake performance of selected MOFs with pre-adsorbed polar (water, alcohols, and amines) and non-polar (toluene and benzene) molecules, as well as some interesting findings from robust computational calculations behind understanding the nature of such host–guest interactions, with the latter one being a practical and useful tool in the research field.