crystals Article Crystallography of Representative MOFs Based on Pillared Cyanonickelate (PICNIC) Architecture Winnie Wong-Ng 1,*, Jeffrey T. Culp 2,3 and Yu-Sheng Chen 4 1 Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA 2 National Energy Technology Laboratory, United States Department of Energy, P.O. Box 10940, Pittsburgh, PA 15236, USA;
[email protected] 3 AECOM, South Park, PA 15219, USA 4 ChemMatCARS, University of Chicago, Argonne, IL 60439, USA;
[email protected] * Correspondence:
[email protected] Academic Editor: Helmut Cölfen Received: 2 July 2016; Accepted: 22 August 2016; Published: 5 September 2016 Abstract: The pillared layer motif is a commonly used route to porous coordination polymers or metal organic frameworks (MOFs). Materials based on the pillared cyano-bridged architecture, [Ni’(L)Ni(CN)4]n (L = pillar organic ligands), also known as PICNICs, have been shown to be especially diverse where pore size and pore functionality can be varied by the choice of pillar organic ligand. In addition, a number of PICNICs form soft porous structures that show reversible structure transitions during the adsorption and desorption of guests. The structural flexibility in these materials can be affected by relatively minor differences in ligand design, and the physical driving force for variations in host-guest behavior in these materials is still not known. One key to understanding this diversity is a detailed investigation of the crystal structures of both rigid and flexible PICNIC derivatives. This article gives a brief review of flexible MOFs. It also reports the crystal structures of five PICNICS from our laboratories including three 3-D porous frameworks (Ni-Bpene, NI-BpyMe, Ni-BpyNH2), one 2-D layer (Ni-Bpy), and one 1-D chain (Ni-Naph) compound.