The effect of pore sizes on D2/H2 separation conducted by MOF-74 analogues

Abstract

Four stable MOF-74 analogues, namely Ni₂(dobdc), Ni₂(dobpdc), Ni₂(olz) and Ni₂(dotpdc), possessing abundant open metal sites (OMSs) and honeycomb channels with pore sizes ranging from 1.0 to 2.6 nm, were used to research the effects of the pore size on D₂/H₂ separation from the hydrogen isotope mixture through dynamic column breakthrough experiments. With respect to consideration of the chemical affinity quantum sieving (CAQS) effect and the competitive adsorption between Ne and hydrogen isotope in (H₂/D₂/Ne: 1/1/98) and (H₂/D₂/Ne: 10/10/80) mixtures, the microporous Ni₂(dobdc) exhibits the longest breakthrough time periods of 240 and 36.4 min g⁻¹, respectively. In the (H₂/D₂: 50/50) mixture, mesoporous Ni₂(olz) exhibits the longest breakthrough time of 15.0 min g⁻¹ owing to its more accessible OMSs and diffusion rate of hydrogen isotope being inclined to adsorb heavier D₂ rather than H₂. Hence, mesoporous MOFs with abundant OMSs may be ideal candidates for D₂/H₂ separation.