Multi‐Occupancy in CO ₂ Clathrate Hydrates: A Quantum Chemistry Study From Finite‐Size Cages to Crystals

This study presents a comprehensive quantum chemistry investigation of multiple CO 2 encapsulation in clathrate hydrates, offering new insights into their potential for high‐capacity gas storage. Dispersion‐corrected density functional theory calculations at the PW86PBE‐XDM and D4 levels were employed to assess the structural stability and energetics of guest‐host systems, focusing on both isolated individual cages and periodic unit cells. Our results reveal that while single CO 2 occupancy remains the most stable configuration for small and medium cages (D, D′, T), the larger H and E cages in sII and sH structures can favorably accommodate up to three and six CO 2 molecules, respectively. Among the hydrate crystals studied, the sII structure demonstrates the most favorable energetics for both single and multiple CO 2 occupancy scenarios, followed by sI and sH. Such detailed bottom‐up approach highlights the importance of guest‐host and guest–guest interactions, providing critical quantitative benchmarks for optimizing CO 2 storage performance. These findings reinforce the relevance of clathrate hydrates as viable candidates for next‐generation environmental applications.