Construction of Mesoporous Frameworks with Vanadoborate Clusters

Abstract

A new porous vanadoborate was synthesized by employing the scale chemistry theory with the vanadoborate cluster V 10 B 28 . The twofold interpenetrated lvt network was assembled with zinc-containing elliptical vanadoborate clusters and Zn polyhedra. The single lvt framework contains a three-dimensional 38 38 20 ring channel system with the pore size (24.7 12.7 ) reaching the mesoscale, thus indicating the possibility of constructing 3D ordered mesopores with vanadoborate clusters. The porosity of the SUT-7 structure was confirmed by CO 2 adsorption of the as-synthesized materials.Crystalline inorganic materials including micro-or/and mesopores are of great importance because of their diverse channel systems and wide applications in adsorption, catalysis, and separation. [1][2][3][4] Mesoporous crystalline materials with a channel size above 2 nm are of special interest as the enlargement of the pores can enhance the diffusion of large organic molecules into the pores when the materials are used as catalysts or supports. However, there are only a few inorganic examples reported with such mesopores, such as ITQ-43[5] (a 28-ring germanium silicate), SU-M, [6] JLG-12 [7] (a 30-ring germanate), ITQ-37 [8] (a 30-ring germanium silicate), and NTHU-13, [9] a series of gallium zincophosphites with ring sizes from 24-ring to 72-ring. Compared to the metal-organic frameworks (MOFs), where the pore size can be expanded and designed in a more rational way through reticular chemistry [4,10] or modular chemistry, [11,12] the expansion of the pore size in the inorganic crystalline materials is much slower. Several strategies [9,13] have been proposed to circumvent this challenge. Müller et al. [14] and Khan [15] introduced linkages between isolated cluster compounds to create porosity, while FØrey [16,17] proposed the scale chemistry method and predicted that the larger the structure building unit (SBU), the larger the pores. Very recently, Wang and coworkers [9] demonstrated that the channels in the phosphate framework can be successfully expanded by using templates with longer carbon chains. Of these three strategies, the first two are very successful with cluster-based building units, such as the germanates. [7,18] Vanadoborates are interesting compounds assembled from vanadoborate clusters. Four types of vanadoborate clusters and their derivatives with different connections of VO 5 and BO 3 /BO 4 polyhedra are mainly reported: V 6 B 20 , [19,20] V 10 B 28 , [21,22] V 12 B 18 , [23][24][25] and V 12 B 16 [23, 26, 27] ( Figure 1). Although these clusters were discovered decades ago, few 3D framework structures have been reported in which they were used as building units. [27,28] In our previous study, we succeeded in linking V 12 B 18 to form the 3D framework SUT-6.[29] The V 12 B 18 cluster in SUT-6 has D 3d point-group symmetry and prefers a six-coordinated net (hxg in SUT-6). This high coordination number of V 12 B 18 makes its surround-

Structural and Electronic Properties of Polyoxovanadoborates Containing the [V12B18O60] Core in Different Mixed Valence States

“…(22), (23), (27), (32), (33), (34), (35), (36), and (37) contain alkaline ions and protonated amine ions with different degrees of protonation. Sodium cations are present in the crystalline lattices of (22), (27), and (32) (36), and 2.140(2) to 3.090(7) Å for (37). The crystalline lattice of the abovementioned systems ( (33)- (37)) is stabilized by the coordination of the potassium cations to the polyoxometalate anions, and by the different modes of hydrogen bonds (unidirectional, bifurcated, and trifurcated) between the protonated amine molecules and the VBO clusters.…”

Application of X-ray Diffraction and Electron Crystallography for Solving Complex Structure Problems

“…). , Single-crystal X-ray diffraction (SCXRD) is the most common technique for structure determination of crystalline materials, as the reflections are separated with very accurate intensities and the phases can be retrieved by the above mentioned algorithms. Several new open framework structures have been determined by SCXRD. − However, SCXRD can only be used for large, high-quality single crystals without mass disorder/defects . When SCXRD fails, powder X-ray diffraction (PXRD) is a standard method for structure determination and phase identification, which provides kinematic and complete data sets that can be collected simply and fast.…”