Na2PbB6O10SO4 and Ca2.58Pb0.42B6O11SO4: First Borate-Sulfates Featuring 3D Porous Borate Anionic Frameworks

Abstract

This study presents two new borate-sulfate compounds, Na2PbB6O10SO4 (I) and Ca2.58Pb0.42B6O11SO4 (II). Both crystals form unique three-dimensional (3D) porous frameworks 3[B6O10]∞ and 3[B7O13]∞, composed by fundamental building blocks [B6O13] and [B7O17], respectively, with [SO4] units embedded within the pores. These examples represent the first observation of 3D borate frameworks in borate-sulfates, thus expanding the structural diversity of borate-sulfate compounds. The relationship between structure and birefringence was studied using first-principles calculations. This study uncovers new insights into the connectivity and structural properties of borate-sulfates.