Synthesis, structure and host-guest properties of (Et4N)2[SnIVCaII(chloranilate)4], a new type of robust microporous coordination polymer with a 2D square grid structure

Reaction of chloranilic acid with SnCl4, Ca(NO3)(2) and Et4NBF4 in aqueous acetone yields (Et4N)(2)[(SnCaII)-Ca-IV(can)(4)]. 2 Me2CO which contains 2D coordination polymer sheets of composition [(SnCaII)-Ca-IV(can)(4)](2-). Both metals are 8-coordinate and act as 4-connecting nodes to form a square grid containing "square" holes. The anionic sheets are electrostatically bound together by Et4N+ cations, which align the sheets so that holes are arranged directly above and below each other, generating channels perpendicular to the sheets. The acetone is easily removed, after which single crystal character is retained. Crystallographic studies indicate that (Et4N)(2)[(SnCaII)-Ca-IV(can)(4)] is able to sorb one molecule per square hole of either acetonitrile, or CS2. Gas sorption measurements indicate that at a pressure of 2000 kPa each square cavity sorbs two CO2 molecules at 273 K, approximately one molecule of N-2 at 195 K and approximately 2.4 molecules of H-2 at 77 K.