Large Breathing Effect Induced by Water Sorption in the Exceptionally Stable Nonporous Non-MOF Crystalline Material

Abstract

We report a non-MOF crystalline material {[Mn(imH)]2[Mo(CN)8]}n (imH = imidazole) with exceptional water sorption properties and a very large breathing effect accompanied by an outstanding stability and cyclability – properties that are absolutely unique for this class of compounds (Prussian Blue Analogs). Some previously published PBAs indeed show some sorption properties, but their cyclability is extremely limited - usually 1-3 cycles - followed by significant decomposition/amorphization. Our compound can be cycled more than 50 times without any fatigue and the sorption/desorption proceeds through four different crystal phases, which we have fully characterized structurally enabling the complete understanding of the sorption and breathing mechanism in this material - an achievement rarely reported for MOFs or PBAs. <br>The unique structure of {[Mn(imH)]2[Mo(CN)8]}n enables very strong coupling of its exceptional water sorption performance with the magnetic and photomagnetic properties of the framework, e.g. the sorption process can be followed by in-situ EPR spectroscopy with huge changes in the EPR signal intensity depending on the hydration level.<br><br>

Magnetic interactions controlled by light in the family of Fe(ii)–M(iv) (M = Mo, W, Nb) hybrid organic–inorganic frameworks

“…The complex magnetic behaviour of Fe 2 Nb results most probably from the hybrid organic-inorganic architecture of this compound with the antiferromagnetic Fe II -NC-Nb IV interactions giving rise to the long-range ferrimagnetic correlation along the inorganic chains, which are further antiferromagnetically coupled to yield a complex 3D magnetic structure. This is in line with our previous studies of Mo IV /W IV photomagnetic assemblies 55,56…”

“…This indicates that octacyanidotungstate(IV) either shows better reversibility of the photo-induced transition or undergoes thermal relaxation in lower temperature range than the octacyanidomolybdate(IV), which is in line with similar previous observations for {[Mn II (imH)] 2 [M IV (CN) 8 ]} n (M = Mo, W) compounds. 55,56…”