Efficient Carbon Capture and Mineralization Using Porous Liquids Comprising Hollow Nanoparticles and Enzymes Dispersed in Fatty Acid-Based Ionic Liquids

Deploying permanent porosity in the liquid phase provides significant opportunities for innovative industrial usage. Liquid-like novel porous materials can thus be employed in continuous flow processes related to toxic gas capture and conversion. Porous liquids (PLs) are a new class of materials that have been used for the capture, sequestration, and separation of various gases. Although, in the past few years, research in this field has garnered a lot of interest, materials that not only combine high fluidity with permanent porosity but also exhibit catalytic activity are still scarce. Here, we show a simple and facile strategy to develop another class of highly stable PLs obtained by the dispersion of surface-engineered hollow silica nanorods in sterically hindered fatty acid (laurate or myristate) and phosphonium-based ionic liquids at room temperature. The PLs show high thermal stability (up to 340 °C) with a rheological behavior suggesting high fluidity (viscosity ∼1.8 Pa•s at 25 °C). Furthermore, the PLs can adsorb gaseous carbon dioxide up to 7.4 folds higher than the pure ionic liquids at low pressure and 25 °C. In a significant advancement, we show that carbonic anhydrase enzyme can be incorporated and stabilized in the PLs to allow in situ biomineralization of carbon dioxide into bicarbonate ions and further conversion to CaCO3. Polarized light and scanning electron microscopy along with PXRD and FTIR studies confirm the coexistence of the calcite, aragonite, and vaterite polymorphs of CaCO3. These findings provide new insights into making fluid-like materials with permanent porosity for low-pressure carbon dioxide uptake and enzyme-based carbon mineralization for the ultimate utility-based materials approach.