Role of boron-containing ionic liquid in the synthesis of manganese borophosphate with extra-large 16-ring pore openings

摘要

An open-framework manganese borophosphate (NH(4))(7)Mn(4)(H(2)O)[B(2)P(4)O(15)(OH)(2)](2)[H(2)PO(4)][HPO(4)] (1) has been synthesized by using 1-butyl-3-methyl-imidazolium bis(oxalato)borate ([C(4)mim][BOB]) ionic liquid as a boron source, and characterized by X-ray powder diffraction (XRD), inductively coupled plasma (ICP), element analysis, thermogravimetric analysis and differential scanning calorimetry (TG-DSC). Single-crystal X-ray diffraction analysis shows that compound 1 crystallizes in orthorhombic space group Pnma (No. 62), a = 17.102(2) angstrom, b = 10.7195(15) angstrom, c = 22.283(3) angstrom, V = 4085.0(10) angstrom(3) and Z = 4. Its structure features an interrupted three-dimensional (3D) open-framework structure built up from [B(2)P(4)O(15)(OH)(2)](6-) borophosphate anions, Mn(2)O(10) dimers and H(x)PW(4)(3-x) (x = 1, 2) groups, where peanut shaped extra-large 16-ring channels can be found extending along the [0 1 0] direction. Protonated NH(3) molecules locate in the void space to balance the negative charges of the inorganic framework. Magnetic measurements indicate that antiferromagnetic interactions exist between Mn(2+) ions with a negative Weiss constant of -18.2 K. The synthesis condition and various impact factors were studied carefully, which indicates that [BOB] anion of ionic liquid and acidity of the system are two important keys for the formation of the title compound. (C) 2011 Elsevier Inc. All rights reserved.