(NH4)6[Mn3B6P9O36(OH)3]·4H2O: A new open-framework manganese borophosphate synthesized by using boric acid flux method

Abstract

A new three-dimensional (3-D) open-framework manganese borophosphate, (NH₄)₆[Mn₃B₆P₉O₃₆(OH)₃]·4H₂O (denoted as MnBPO-CJ31), has been synthesized by using boric acid flux method. Its anionic framework structure is constructed by the connection of MnO₆ octahedra and BO₄, PO₄ and PO₃(OH) tetrahedra. It contains 12-ring channels along the [001] direction with a pore diameter of 7.1 Å. It is the first borophosphate featuring a 3-D anionic partial structure with a B/P ratio of 2/3 and an unprecedented fifteen mer tetrahedral fundamental building unit (FBU) [B₆P₉O₃₆(OH)₃] exists in this compound. NH₄⁺ ions locate in the void space to balance the negative charge of the inorganic framework. The compound is further characterized by powder XRD, ICP, CHN, TGA and IR analyses. Magnetic study reveals that MnBPO-CJ31 shows interesting canted antiferromagnetic behaviour at low temperature.