Survey on the Phase Transitions and Their Effect on the Ion-Exchange and on the Proton-Conduction Properties of a Flexible and Robust Zr Phosphonate Coordination Polymer

Abstract

The flexible zirconium tetraphosphonate coordination polymer with formula Zr(O(3)PCH(2))(2)N-C(6)H(10)-N(O(3)CH(2)P)(2)X(2-x)H(2+x)·nH(2)O (X = H, Li, Na, K, 0 < x < 1, 4 < n < 7.5) (1) possesses an open framework structure with 1D cavities decorated with polar and acids P═O and P-OH groups. 1 has been fully protonated by adding HCl and then subjected to several acid-base ion-exchange reactions with alkaline metals hydroxides. 1 is a very robust coordination polymer because it can be regenerated in H- form using strong acid solutions and ri-exchanged several times without hydrolysis and loss of crystallinity. The flexibility of 1 has been also studied by means of TDXD (temperature dependent X-ray diffraction) evidencing remarkable phase transformations that lead to a different disposition of the water molecules. These transformations also influence the accessibility of the cations on the P-OH groups placed inside the channels and thus the ion-exchange properties. The dependence of the proton conductivity properties on these phase transitions has been also investigated and discussed.

Brønsted Acidity in Metal–Organic Frameworks

“…Examples of MOFs consisting of organophosphonic acid and other transitional metals (Ce, Pr, Sm, Eu, Gd, Tb, Dy, and Zr) were also reported to show moderate proton-conducting properties. 223,224 Another approach, combining MOFs and original protonconducting materials, was also proposed and successfully realized. Hybrid compounds consist of CsHSO 4 , the protonconducting M m H n (XO 4 ) p family, and MIL-101, formulated as (1-x)CsHSO 4 ·xMIL-101 (x = 0−0.07), where x stands for the mole fraction of MIL-101 in the nanocomposite system.…”

Overcoming the crystallization and designability issues in the ultrastable zirconium phosphonate framework system

“…By contrast, Zr 6 clusters are found in several benchmark zirconium carboxylate MOFs UiO-66, PCN-222, MOF-525 and other compounds132526272829, while NU-1000 contains a Zr 8 cluster as the SBU30. As another consequence, zirconium phosphonates with 3D framework structures are quite rare24313233. Among these, only UPG-1, whose structure was solved by powder X-ray diffraction recently, shows permanent porosity33.…”

Solvent-dependent Assembly of Discrete and Continuous CoCl2 Adamantane-based Ligand Complexes: Observations by CSI–Mass Spectrometry and X-ray Crystallography

“…Coordination polymers (CPs) and metal-organic frameworks (MOFs) are well-known crystals constructed by an organic compound and a metal. Porous CPs (PCPs) and MOFs, in particular, are highly potential materials for gas storage, [22][23][24] ion exchange, [25][26][27][28] heterogeneous catalysis, [29][30][31] separation, 29,[32][33][34][35][36] and non-linear optics, [37][38][39] because of the nanospace separated from bulk space.…”