Controllable preparation and structures of two zinc phosphonocarboxylate frameworks with MER and RHO zeolitic topologies

Abstract

3-Phosphonobenzoic acid (3-H₃pbc) was designed as an extended 4-connected ligand to build zeolite-like metal–organic frameworks (ZMOFs). Controlled assembly of Zn²⁺ with ligand 3-H₃pbc results in two distinct structures with zeolitic topologies of MER and RHO, namely [Zn(3-pbc)]·H₃O·0.5H₂O (1) and Zn_2.5(3-pbc)₂(H₂O)·nS (S represents the disordered solvent molecules) (2), respectively. The framework of 1 consists of double crankshaft chains formed by alternating ZnO₄ and O₃PC tetrahedra that are cross-linked by 3-pbc to generate a three-dimensional zeolitic open-framework. It is worth noting that structure 2 builds a zeolitic framework in a novel way, which has not been found in other metal phosphonocarboxylates. The organic part of 3-pbc does not participate in the construction of zeolitic topology and only plays a decorative role inside the cages.