Encapsulation of small molecules in two-dimensional clathrate hydrates

We performed first-principles computations to investigate four new structures of two-dimensional hydrates (denoted as TDH-I, TDH-II, TDH-III, and TDH-IV), and to evaluate their potential applications in gas separation for CH4, CO2, N-2 and NH3. The lattice parameters, the cage occupancy, and the energetic stability of the hydrates are determined and compared, and it is feasible to use the studied hydrates for gas separation. On the other hand, the dynamic analysis shows that these hydrates can exist stably in a highly confined environment, following the order of N-2 > CO2 > NH3 > CH4, and that the kinetic diameter of gas molecules play a primary role in stabilizing the hydrate structure. As the temperate increases, the dynamic stability of the hydrates decreases, but they can still be stabilized at a temperature of 270 K.