Single-Crystal-to-Single-Crystal Structural Transformation in a Flexible Porous Gadolinium-Organic Framework with Selective and Controlled Sorption Properties

A novel pillared-bilayer gadolinium-organic framework, {[Gd2(dhbdc)(dhbdcH2)(H2O)5]·2H2O)}n (1), (dhbdcH4 = 2.5-dihydroxyterephthalic acid), has been synthesized using hydrothermal technique and structurally characterized. 2D pillared-bilayer networks are interdigitated and H-bonded, forming a 3D supramolecular framework with two different channels along the c-axis. Framework exhibits stepwise release of the guest and coordinated water molecules and reversible single-crystal-to-single-crystal structural transformation upon removal and reintroduction of the guest water molecules. Partially dehydrated frameworks, {[Gd2(dhbdc)(dhbdcH2)(H2O)5]}n (1′) and {[Gd2(dhbdc)(dhbdcH2)(H2O)4]}n (1′′) show different sorption capacity of N2 realized by structural contraction in 1′′. Framework 1′′ reveals strong hydrophilic character compare to 1′ and both the frameworks 1′ and 1′′ do not uptake other organic vapors like MeOH, CH3CN, and EtOH, suggesting size dependence in sorption properties.