Hydrogen isotope separation on nickel-containing metal-organic framework@gama-alumina-based multicomponent composite packed column: Identification of individual role of each component.

Abstract A new optimized multicomponent composite, Na2Cr2O7/Na2CrO4/NaCl/MOF-74(Ni)@γ-Al2O3 (S1/S2/S3/MOF-74(Ni)@γ-Al2O3. Na2Cr2O7 = S1, Na2CrO4 = S2, NaCl = S3), was prepared and used as a gas chromatography stationary phase for the separation of H2 and D2 isotopes. Under the optimal chromatographic separation conditions, the resolution of the packed column for the separation of H2/D2 was 2.87, and the separation time was 7.15 min at 77 K. The control experiments showed that in the multicomponent composite, MOF-74(Ni), which has a chemical affinity quantum sieving effect, played a major role in the separation of H2/D2. As the support of MOF-74, γ-Al2O3 enhanced the mechanical strength of MOF-74 and reduced the gas resistance. The presence of Na2CrO4 in the column increased the H2/D2 separation resolution, while the presence of NaCl reduced the separation time, produced more symmetrical and narrow chromatographic peaks of Gaussian distribution. Furthermore, by optimizing the ratio of NaCl and Na2CrO4, (S2/S3/MOF-74(Ni)@γ-Al2O3) composite with a NaCl/Na2CrO4 mass ratio of 0.7:1 was synthesized and used to realize the high-resolution separation of H2/D2 (R = 2.56) with a short separation time (t = 5.91 min). Both composites also showed excellent repeatability/reproducibility for separation.