Two New Nonaborates with {B(9)} Cluster Open-Frameworks and Short Cutoff Edges

Two new nonaborates, Na(2)Ba(0.5)[B(9)O(15)]·H(2)O (1) and Na(4)Ca(1.5)[B(9)O(16)(OH)(2)] (2), have been solvothermally made with mixed alkali and alkaline-earth metal cationic templates. 1 and 2 are constructed by two different types of nonaborate clusters. In 1, the [B(9)O(19)](11−) cluster is composed of three corner-sharing [B(3)O(7)](5−) clusters, of which two of them interconnect to the 1D B(3)O(7)-based chains and are further bridged to the 3D framework with 7 types of 10-MR channels by another [B(3)O(7)](5−) bridging cluster. The [B(9)O(18)(OH)(2)](11−) cluster in 2 is made of four BO(4)-sharing [B(3)O(8)](7−) clusters. As a 4-connected node, the interconnections of [B(9)O(18)(OH)(2)](11−) construct the unpreceded 2D layer with large 14-MR windows, which are further joined by H-bonds to the 3D supramolecular framework. UV–Vis absorption spectra reveal that both 1 and 2 have short cutoff edges below 190 nm, exhibiting bandgaps of 6.31 and 6.39 eV, respectively, indicating their potential applications in deep UV (DUV) regions.