Tuning the gate opening pressure of a flexible doubly interpenetrated metal–organic framework through ligand functionalization

Abstract

A functional doubly interpenetrated MOF [(Zn₄O)₂(MDCPB)₆DMF]·3DMF·3H₂O (JLU-Liu33F, H₂MDCPB = 5-methyl-1,3-di(4-carboxyphenyl)benzene, DMF = N,N-dimethylformamide) with pcu topology has been solvothermally synthesized. JLU-Liu33F (F = functionalization) is the isostructural analogue of JLU-Liu33, which is constructed by –CH₃ functional V-shaped ligand and a classical Zn₄O cluster. Similar to the adsorption property of JLU-Liu33, JLU-Liu33F also exhibits breathing behavior upon N₂ and CO₂ adsorption at 77 and 195 K, respectively. However, due to the introduction of –CH₃ functional groups, the interpenetration degree of JLU-Liu33F become closer to that of JLU-Liu33, which results in higher gate opening pressures for both N₂ and CO₂ adsorption. Moreover, the breathing behavior of JLU-Liu33F for C₂H₆ and C₃H₈ adsorption disappeares. Moreover, JLU-Liu33F also exhibits commendable selectivity for C₂H₂ over CH₄.