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, {[Gd 2 (dhbdc)(dhbdcH 2 )(H 2 O) 5 ]2H 2 O)} n (1), (dhbdcH 4 = 2.5-dihydroxyterephthalic acid), has been synthesized using hydrothermal technique and structurally characterized. 2D pillaredbilayer 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, {[Gd 2 (dhbdc)(dhbdcH 2 )(H 2 O) 5 ]} n (1′) and {[Gd 2 (dhbdc)(dhbdcH 2 )(H 2 O) 4 ]} n (1″) show different sorption capacity of N 2 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, CH 3 CN, and EtOH, suggesting size dependence in sorption properties.