Nanoengineered metal@zeolite materials have recently emerged as a promising class of catalysts for several industrially relevant reactions. These materials, which consist of small transition metal nanoclusters confined within three-dimensional zeolite pores, are interesting because they show higher stability and better sintering resistance under reaction conditions. While several such hybrid catalysts have been reported experimentally, key questions such as the impact of the zeolite frameworks on the properties of the metal clusters are not well understood. To address such knowledge gaps, in this study, we report a robust and transferable machine learning-based potential (MLP) that is capable of describing the structure, stability, and dynamics of zeolite-confined gold nanoclusters. Specifically, we show that the resulting MLP maintains ab initio accuracy across a range of temperatures (300-1000 K) and can be used to investigate time scales (>10 ns), length scales (ca. 10,000 atoms), and phenomena (e.g., ensemble-averaged stability and diffusivity) that are typically inaccessible using density functional theory (DFT). Taken together, this study represents an important step in enabling the rational theory-guided design of metal@zeolite catalysts.

In the context of carbon reutilization, the direct electroreduction of captured CO₂ (c-CO₂RR) appears as an appealing approach since it avoids the energetically costly separation of CO₂ from the capture agent. In this process, CO₂ is directly reduced from its captured form. Here, we investigate the influence of the capture agent and proton source on that reaction from a combination of theory and experiment. Specifically, we consider methoxide-captured CO₂, NH₃-captured CO₂, and bicarbonate on silver electrocatalysts. We show that the proton source plays a key role in the interplay of the chemistries for the electroreduction of protons, free CO₂, and captured CO₂. Our density functional theory calculations, including the influence of the potential, demonstrate that a proton source with smaller pK_a improves the reactivity for c-CO₂RR, but also increases the selectivity toward the hydrogen evolution reaction (HER) on silver surfaces. Since c-CO₂RR requires an additional chemical protonation step, the influence of the proton source is stronger than that of the HER. However, c-CO₂RR cannot compete with the HER on Ag, Experimentally, the dominant product observed is H₂ with low amounts of CO being produced. Through a rotating cylinder electrode cell of well-defined mass-transport properties, we conclude that although methanol solvent exhibits a lower HER activity, HER remains dominant over c-CO₂RR. Our work suggests that methoxide is a potential alternative capture agent to NH₃ for direct reduction of captured CO₂, though challenges in catalyst design, particularly in reducing the onset potential of c-CO₂RR to surpass the HER, remain to be addressed.