Background and Motivation: Integrated Carbon Capture and Utilisation (ICCU) using Dual Function Materials (DFMs) presents a highly promising, energy-efficient pathway for mitigating anthropogenic CO₂ emissions. While DFMs have demonstrated commercial viability for high-temperature methanation, the direct, ambient-pressure conversion of captured CO₂ into high-value liquid oxygenates, such as methanol, remains a significant catalytic challenge. This thesis investigates the fundamental mechanistic and thermodynamic barriers of DFMs for low-pressure methanol synthesis, focusing on the complex interplay between active metal phases, support architectures, and basic alkaline adsorbents.

Methodology: A series of adsorbents, catalysts and composite DFMs were synthesised via wet impregnation. While literature indicates that In₂O₃/ZrO₂ systems achieve high methanol selectivity at elevated pressures, we initially hypothesised that they might still operate at atmospheric pressure, albeit with lower activity and selectivity. However, to ensure robust methanol production under ambient conditions, we strategically transitioned to Palladium (Pd)-based catalysts supported on active (ZnO) and inert (SiO₂) matrices, guided by literature demonstrating successful ambient-pressure methanol synthesis over Pd/ZnO. Calcium Oxide (CaO) was incorporated and optimised as the primary adsorbent component. A systematic approach to catalyst synthesis was adopted, beginning with the tuning of the support materials' CO₂ adsorption strength. Subsequently, the active catalyst was incorporated, enabling a detailed investigation of the proximity paradox between the adsorption and catalytic sites. To evaluate the success of this synthesis strategy, the structural, electronic, and dynamic properties of these materials were systematically characterised using XRD, XPS, SEM-EDX, H₂-TPR, and CO₂-TPD. Catalytic performance was evaluated under both continuous steady-state hydrogenation and dynamic Temperature-Programmed Surface Reaction (TPSR) ICCU cycles at atmospheric pressure.

Results: To advance the engineering of DFMs beyond conventional macroscopic mixtures, it was first necessary to develop a novel bifunctional support. By incorporating CaO into an active ZnO matrix, this study revealed a fundamental trade-off between chemical activity and physical texture, demonstrating that 5 weight percentages (wt.%) CaO achieved optimal dispersion and maximized CO₂ capture via highly stable surface carbonates. Building upon these optimised sorbents, Pd was subsequently incorporated. Steady-state catalytic evaluations confirmed that while an inert SiO₂ support stabilized pure metallic Pd⁰ to exclusively promote methanation, the ZnO support facilitated the in-situ formation of an intermetallic PdZn alloy, which effectively suppressed C-O bond cleavage and drove high methanol selectivity.

   Crucially, moving beyond the steady-state evaluations common in previous literature, testing under dynamic ICCU conditions exposed a previously uncharacterized "Proximity Paradox." While the PdCaO/SiO₂ DFM successfully converted captured CO₂ to methane, the methanol-selective PdCaO/ZnO DFM experienced total dynamic catalytic failure. Comprehensive characterisation proved this to be a fundamental thermal mismatch rather than chemical instability of the PdZn alloy where the highly basic support locked captured CO₂ at desorption temperatures far exceeding the thermodynamic limits of methanol synthesis. Overcoming this novel challenge, a ternary PdZn-CaO/SiO₂ system was developed, successfully utilizing inert silica to weaken CO₂ binding while maintaining the active alloy phase for dynamic methanol synthesis. Finally, expanding the catalytic test space, In₂O₃/ZrO₂-based systems were evaluated, revealing for the first time that the addition of basic CaO sorbents at low pressures fundamentally alters the reaction pathway toward undesired methanation.

Conclusions: This research identifies a fundamental "Proximity Paradox" in DFM design: the intimate solid-state integration of CaO and ZnO required for catalytic spillover creates an highly basic interface. This interface forms stable carbonates that require temperatures exceeding 550 ℃ to desorb, creating a substantial thermal mismatch with the strict 200-300 ℃ operating window required for the catalytic methanol synthesis step. Furthermore, physical separation of the sites disrupts intermediate transport and induces alloy oxidation. Consequently, the successful development of ambient-pressure, methanol-producing DFMs will require the advanced nanoscale tuning of sorbent basicity or the strategic spatial segregation of capture and catalytic sites (e.g., core-shell architectures) to bridge this critical thermal gap. Ultimately, by elucidating the precise molecular and thermodynamic origins of this paradox, this research provides a foundational blueprint for next-generation material design. It demonstrates that achieving a circular carbon economy via decentralised ICCU will depend upon the precise nanoscale synchronisation of capture and conversion operating windows, supported by rigorous future techno-economic assessments.