Examples of hydrothermal titration and real time X-ray diffraction in the synthesis of open frameworks

Hydrothermal titration (HTT) techniques represent a new synthetic strategy for the production of open frameworks. As an example, initial digestion of amorphous GeS₂ in the presence of tetraethyl ammonium hydroxide (TEAOH) at 100 °C is followed by injection of Ag⁺ into this mixture to condense the [Ge₄S₁₀]^4- clusters and form a framework consisting of 8-ring channels bounded by alternating GeS-clusters and Ag⁺. The rational use of this apparatus depends upon determining the timing of injection. Insight into the changes occurring during reactant digestion is provided by real time synchrotron X-ray powder diffraction. Changes in the system dimethylamine-Sb-S have been followed in real time at different temperatures. The transformation from mixtures of DMA, Sb and S to the known open phase DMA-SbS-SB8 was followed by observing monochromatic X-ray scattering detected on an imaging plates over a 8 hr period with one continuous exposure.