Behavior of Microporous Nitroprussides in Presence of Ammonia

摘要

The behavior of microporous nitroprussides in the presence of ammonia, both in anhydrous and hydrated states, was studied using ammonia adsorption isotherms and IR, Moessbauer and XRD techniques. In their anhydrous state these materials behave as a zeolite for ammonia adsorption, however when structural water is present a decomposition process was observed. The crystallization or adsorbed water is used by ammonia to form NH_4~+ and OH~-, creating basic conditions where the structural building unit [Fe(CN)_5NO] loses the NO group to form a pentacyano complex. This leads to the formation of mixed salts, M(NH_4)[Fe(CN)_5]·xH_2O. For ferrous nitroprusside the formed OH~- ion competes with the complex anion for the iron(2+) cation which is removed, then oxidized and finally observed as a ferric oxyhydroxide, FeOOH.