Efficient hexane isomers separation in isoreticular bipyrazolate metal-organic frameworks: The role of pore functionalization

Hydrocarbons separation in petrochemical industries is a key, energy-consuming stage in the manufacture of high-quality added-value products—hence the need for more efficient materials and environmentally friendly methodologies to improve this process. In this context, we have studied the effect of metal-organic frameworks (MOFs) pore functionalization in hexane isomers separation, isolating the robust isoreticular zinc(II) bipyrazolates Zn(BPZ), showing no pore decoration, Zn(Me₂BPZ), the pores of which are decorated with apolar methyl groups, and Zn(BPZ(NH₂)₂), the spacers of which possess polar Lewis-basic functions (H₂BPZ = 1H,1’H-4,4’-bipyrazole; H₂Me₂BPZ = 3,3’-dimethyl-1H,1’H-4,4’-bipyrazole; H₂BPZ(NH₂)₂ = 3,5-diamino- 1H,1’H-4,4’-bipyrazole; DMF = dimethylformamide). After characterizing Zn(BPZ(NH₂)₂) as per its crystal structure and thermal behaviour, and all the three MOFs as per their textural properties, we investigated, from the experimental and computational points of view, the impact of the square one-dimensional channels decoration on the separation of the hexane isomers, demonstrating the relevance of pore constrictions in the resolution of the title alkanes mixture.