The separation of hydrogen isotopologues, such as protium (H2), deuterium (D2) and tritium (T2), is necessary for the 

stable and consistent operation of heavy water nuclear power plants, where deuterium oxide (D2O) is used as both a 

moderator and coolant. As conventional processes, cryogenic distillation and catalytic exchange are widely applied for 

hydrogen isotopologues separation. However, those techniques encounter intrinsic limitations including high energy consumption,

slow reaction rates and large operational costs. As an alternative, separation techniques based on the mechanism 

of chemical affinity quantum sieving have been studied to separate isotopes at liquid nitrogen (N2, 77 K) to upwards 

through differences in adsorption. In this study, mesoporous silica modified with silver (Ag) or copper (Cu) was prepared 

and applied for hydrogen isotopologues separation at 77 and 87 K. The structural, morphological and surface chemical 

properties of the metal incorporated mesoporous silica were analyzed using X-ray diffraction, scanning electron microscopy,

transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, N2 physisorption, X-ray photoelectron

spectroscopy and solid-state silicon-29 magic angle spinning nuclear magnetic resonance spectroscopy. Single 

gas adsorption isotherms of H2 and D2 were measured. The isosteric heats of adsorption were calculated to compare 

how strongly each hydrogen isotopologues interact with the adsorbents and binary separation performance was evaluated 

using equilibrium modeling. The Cu incorporated mesoporous silica showed the highest D2 over H2 selectivity, reaching 

5.52 under the D2 diluted conditions (1:99). This is attributed to the dispersed Cu oxide species in the silica framework 

as well as the silanol rich domains of mesoporous silica which both enhance interaction with D2. These results suggest 

that isotope selectivity (D2/H2) can be tuned by adjusting the surface structure, property and pore network of mesoporous 

silica, offering a practical approach for hydrogen isotopologues separation in nuclear facility