A rhombus channel metal–organic framework comprised of Sr2+ and thiophene-2, 5-dicarboxylic acid exhibiting novel dielectric bistability

Abstract

A metal–organic framework (MOF) compound, comprised of Sr²⁺ and thiophene-2,5-dicarboxylic acid (H₂TDA) with a formula of Sr(TDA)(DMF), was prepared via the solvothermal method, this MOF compound crystallizes in the monoclinic space group P2₁/c with unit cell parameters a = 6.0078(4) Å, b = 16.9401(12) Å, c = 13.0061(8) Å, β = 116.158(3)° and V = 1188.10(14) ų. The spaces of rhombus channels in the MOF crystal are occupied by the disordered DMF molecules. The striking structural feature is that the connectivity between inorganic hendecahedron units of SrO₇ and TDA²⁻ ligands gives rise to the uncommon I¹O² type 3-D framework of 1. The dielectric relaxation and novel dielectric bistability behaviors were observed for this MOF compound in the lower frequency regime (f < 10³ Hz) and the higher temperature (T > 160 °C), which originated from the orientation motion of the disordered polar DMF molecules under an ac electric field. This study suggested the possibility of dielectric bistability in the designed MOFs with pores or channels.