Porous liquids – Future for CO<inf>2</inf> capture and separation?

Porous liquids form a new class of materials, which are liquid at room temperature and possess permanent porosity. The latter is a characteristic generally associated with solid-state only. Since the idea of porous liquid was exploited over a decade ago, the researchers see an opportunity of solving the solid material's limitation in gas capture and separation. In this discussion, we present the most recent developments on porous liquids and, in our perspectives, how they can tackle energy and environmental issues by their coupling with membrane technology. In a broader context, the need to reduce greenhouse gas, chlorofluorocarbons and other gaseous emissions is essential for tackling climate change and to achieve the 2015 Paris Agreement goals. In addition, the energy used for chemical separations in industrial processes accounts for 10–15% of the world's energy consumption. Thus, improved separation technologies will reduce energy consumption and the spreading of negative-emission technologies such as carbon capture sequestration and utilization (CCSU). Despite the imperative necessity of CCSU, many candidates are still considered the key technology due to the complex balancing between economic, technical and ecological advantages and drawbacks. Porous materials, which are usually solids, are of great interest for absorption due to the presence of permanent cavities, but liquids are easier to handle at the industrial scale. Porous liquids are a good compromise between these two traditional classes of materials.