Flexibility and Sorption Selectivity in Rigid Metal–Organic Frameworks: The Impact of Ether‐Functionalised Linkers

The functionalisation of well‐known rigid metal–organic frameworks (namely, [Zn 4 O(bdc) 3 ] n , MOF‐5, IRMOF‐1 and [Zn 2 (bdc) 2 (dabco)] n ; bdc=1,4‐benzene dicarboxylate, dabco=diazabicyclo[2.2.2]octane) with additional alkyl ether groups of the type ‐O‐(CH 2 ) n ‐O‐CH 3 ( n = 2–4) initiates unexpected structural flexibility, as well as high sorption selectivity towards CO 2 over N 2 and CH 4 in the porous materials. These novel materials respond to the presence/absence of guest molecules with structural transformations. We found that the chain length of the alkyl ether groups and the substitution pattern of the bdc‐type linker have a major impact on structural flexibility and sorption selectivity. Remarkably, our results show that a high crystalline order of the activated material is not a prerequisite to achieve significant porosity and high sorption selectivity.