Synthesis and Single Crystal X-ray Structure of the Monoclinic Sodium Copper Borate (Na2Cu2B12O21)

Abstract

Sodium copper borate, Na 2 Cu 2 B 12 O 21 , is a member of the Na 2 M 2 B 12 O 21 (M(II) = Ni, Cu and Co) structure type. It has been synthesized by a solid-state reaction. Single-crystal XRD analysis showed that it crystallizes in the monoclinic system, I 2/a space-group with a = 17.353(1), b = 4.671(1), c = 19.672(1)Å, ß= 101.42(1)°, Z = 4. The new anhydrous borate shows a 3-D framework crystal structure. It contains a discernible tunnel structure constructed from BO 4 tetrahedra, BO 3 trigonal units and CuO 6 octahedra. Seven-coordinate Na + cations lie in the large tunnels that extend along the b axis. This structural model is validated by the charge distribution (CD) analysis.

Thermodynamic properties of two microporous materials for Na 2 [M 2 B 12 O 21 ] (M = Co 2+ , Cu 2+ )

“…b Standard uncertainties u are u (T) = 0.001 K, u (p) = 2 kPa, and u (m) = 0.01 mg. c Expanded uncertainty U, which was estimated as twice the standard deviation of the mean with 0.95 level of confidence. À262.08 ± 0.60 [13] (4) 2Na + (aq) + 2Cl À (aq) + 12H 3 À262.08 ± 0.60 [13] (4) 2Na + (aq) + 2Cl À (aq) + 12H 3 À992.70 ± 0.60 [17] (7) 2CuCl 2 Á2H 2 O(s) = 2Cu(s) + 2Cl 2 (g) + 4H 2 (g) + 2O 2 (g)…”

“…The microporous crystal samples were synthesized referring to literature [2,3] by using high temperature solid-state reactions. All reagents used in the synthesis were of analytic grade.…”

“…Until now, the boron atom has been introduced in several frameworks of microporous material systems, such as B-O-M (transition metal) system. Many transition metal borates have been synthesized, some of which possessed three-dimensional open framework structures and might be used as microporous materials, such as two transition metal borates with microporous structures, Na 2 Co 2 B 12 O 21 [2] and Na 2 Cu 2 B 12 O 21 [3].…”