Interaction profiles of dioxane and thf ether stabilizers with CH₄, CO₂ and H₂ gas molecules in doublecaged clathrate hydrate system

Clathrate hydrates, also known as gas hydrates, are compounds composed of three-dimensional hydrogen-bonded water molecules that form cage-like structures capable of trapping small gas molecules. The stability of these cages can vary depending on the chemical nature of the host–guest interactions between the water framework and the trapped gas molecules, as well as the type of cage (small or large). In this thesis, the host–guest interactions between dioxane and tetrahydrofuran (THF) ether molecules in the large cages, and methane (CH₄), carbon dioxide (CO₂), and hydrogen (H₂) molecules in the small cages of binary clathrate hydrate systems, were theoretically investigated. The theoretical studies were carried out using the Gaussian16 software at the M06-2X/cc-pVDZ level, and geometric optimizations of the sII-type double cage systems were performed. According to the computational results, the lowest total interaction energy was calculated as −14.99 kcal/mol for the structure containing CO₂ in the small cage and 1,4-dioxane in the large cage. It was specifically determined that 1,4-dioxane, due to its six-membered ring structure with two oxygen atoms, fits more compatibly into the cage structure compared to THF, and forms stronger interactions with water molecules, thereby significantly enhancing the overall stability of the system. Topological analyses revealed that non-classical weak hydrogen bonds and van der Waals interactions play a critical role in the stability of these molecular systems and directly influence the energy profile of the system.