Construction of Alkali‐metal‐based Imidazolecarboxylate Coordination Polymers as Efficient Catalysts for Solvent‐free Ring‐opening polymerization of ϵ‐Caprolactone

Abstract A series of new alkali‐metal‐based coordination polymers, [Li(H2IMDC)(H2O)]n (1), [Na2(H2IMDC)2(H3IMDC)2(H2O)4]n (2), and [K(H2IMDC)(H2O)]n (3), have been constructed under solvothermal conditions by using imidazole‐4,5‐dicarboxylic acid (H3IMDC) as ligand. The structure of the complexes has been determined by single‐crystal X‐ray diffraction and further characterized by elemental analyses, IR spectra, powder X‐ray diffraction and thermogravimetric analyses. The single crystal X‐ray structural studies showed that their structural dimensionalities varying from 1‐D zigzag chain, 2‐D 44‐sql network to 3‐D 4,6‐connected coordination framework are strongly governed by the ionic radii and coordination geometries of the metal cations. For the first time, the alkali‐metal‐based coordination polymers were demonstrated to be effective catalysts for the solvent‐free ring‐opening polymerization (ROP) of ϵ‐caprolactone. The catalytic activity of complexes 1–3 depends on the metal cations, increasing in the order Li+ < Na+ < K+.