Automated Discovery and Screening of Stimuli-Responsive Porous Liquids

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Porous liquids are an emerging class of porous materials that combine the properties of a microporous solid with the fluidity of a liquid. By incorporating intrinsic porosity in these liquids, properties that are difficult to achieve with conventional non-porous liquids are accessible, such as increased gas uptake and guest selectivity due to the presence of permanent tailorable pores. A range of porous liquids have now been reported, developed by translating porous solids into the liquid state, including porous organic cages (POCs), metal-organic cages (MOCs), covalent-organic frameworks (COFs), and metal-organic frameworks (MOFs). The gas capacity of these different porous liquids has been quite widely studied, with subsequent release of the gas relying on molecular displacement with liquid guests, pressure or temperature swings, or sonication. Recently, we reported the formation of high cavity concentration porous liquids using POCs - discrete molecules containing permanent molecular cavities accessible through windows - and demonstrated their ability to exhibit increased uptake of a range of gases (e.g., CO2, CH4, Xe, SF6) over neat liquids (Nature, 2015, 527, 216; Chem. Sci., 2017, 8, 2640; Angew. Chem. Int. Ed., 2020, 59, 7362; Adv. Funct. Mater., 2021, 31, 2106116). Despite these advances, the incorporation of stimuli-responsive porous materials into porous liquids, such as fluorescent or photoresponsive species, is much less investigated, but could offer additional advantages and/or use in different applications. For example, fluorescent porous liquids could be used as small molecule sensors, and photoresponsive liquids could enable controlled gas release using light. Recent proof-of-concept studies in the Greenaway group have proven that both types of these stimuli-responsive porous liquids are accessible, but the design and synthesis of both the initial porous material and subsequent porous liquid was time-consuming and the resultant material properties non-optimised. This project will build on these initial results, and our previous work on high-throughput POC synthesis and porous liquid discovery (Nature Commun., 2018, 9, 2849; Chem. Sci., 2019, 10, 9454), to screen and develop new stimuli-responsive porous liquids, followed by high-throughput screening of both their porous and optical properties (fluorescence, photoswitching).