Structures of dehydrated microporous copper silicate CuSH-6Na, an in situ single crystal X-ray study

Abstract

Abstract The dehydration behavior of the microporous copper silicate Na2(Cu2Si5O13)·3H2O conventionally denoted as CuSH-6Na was studied using single crystal X-ray data collected at temperatures –150, 25, 40, 50, 60, 70 and 120 °C. Reversible dehydration of CuSH-6Na starts at ambient temperatures under dry nitrogen flow and is complete at 70 °C. The water molecules initially present in both ordered and disordered sites were simultaneously driven out beginning at ambient temperature. The dehydration is accompanied by a negative thermal expansion of the crystal caused by a slight progressive narrowing of the channels along the direction perpendicular to the silicate layers. The fully dehydrated structure has framework copper metal sites with open coordination spheres directly exposed to the space inside the accessible channels.