Engineering Structural Dynamics of Zirconium Metal–Organic Frameworks Based on Natural C4 Linkers

Engineering
the structural flexibility of metal–organic
framework (MOF) materials for separation-related applications remains
a great challenge. We present here a strategy of mixing rigid and soft linkers in a MOF structure to achieve
tunable structural flexibility, as exemplified in a series of stable
isostructural Zr-MOFs built with natural C4 linkers (fumaric acid,
succinic acid, and malic acid). As shown by the differences in linker
bond stretching and bending freedom, these MOFs display distinct responsive
dynamics to external stimuli, namely, changes in temperature or guest
molecule type. Comprehensive in situ characterizations
reveal a clear correlation between linker character and MOF dynamic
behavior, which leads to the discovery of a multivariate flexible
MOF. It shows an optimal combination of both good working capacity
and significantly enhanced selectivity for CO2/N2 separation. In principle, it provides a new avenue for potentially
improving the ability of microporous MOFs to separate other gaseous
and liquid mixtures.