Carbon dioxide (CO2) is a renewable carbon source that can be used as a C1 building block to produce fuels and chemicals via carbon capture and utilisation technologies. Designing a process that integrates CO2 capture with utilisation steps and which is flexible enough to keep up with the fluctuations in supply and demand can be an out-of-the-box solution to produce on-demand chemicals, making these technologies financially appealing.

The NiRu/CeAl catalyst, presented in this thesis, demonstrated a high activity in the CO2 methanation, reverse water-gas shift (RWGS), and dry reforming of methane (DRM) reactions and showed promising stability results in a 60-hr cycle of methanation-RWGS-DRM. This formulation was used as the basis for switchable dual-function materials (DFMs), and a successful proof-of-concept study was performed using Na2O, K2O, and CaO as adsorbents. The designed switchable DFMs captured CO2 at a range of temperatures and converted it into CH4, CO, or syngas by using either H2 or CH4 as a co-reactant. By conducting mechanistic studies during cyclic operation, dissociation of CO2 and formation of carbonates species were observed, and the desired product was formed at the specified conditions through formyls. When the Ca-containing DFM was tested under a real flue gas (fermentation off-gases from a brewery), it manifested a stable CH4 capacity over time, despite the presence of O2 and H2O. The techno-economic feasibility of switchable catalysis was also assessed, which revealed a carbon-negative and profitable process, mainly due to the production of synthetic natural gas.

Overall, this thesis presents a new generation of integrated CO2 capture and conversion materials that can capture CO2 from any source that contains it, ranging from ambient air to pure streams, and convert it into the desired product by changing the co-reactant and temperature, thus providing the world with an one-stop shop solution for a net-zero future.