We show that metal-organic frameworks,based on tetrahedral pyridyl ligands,can be used as a morphological and structural template to form a series of isostructural crystals having different metal ions and properties.An iterative crystal-to-crystal conversion has been demonstrated by consecutive cation exchanges.The primary manganese-based crystals are characterized by an uncommon space group(P622).The packing includes chiral channels that can mediate the cation exchange,as indicated by energy-dispersive X-ray spectroscopy on microtome-sectioned crystals.The observed cation exchange is in excellent agreement with the Irving-Williams series(MnZn)associated with the relative stability of the resulting coordination nodes.Furthermore,we demonstrate how the metal cation controls the optical and magnetic properties.The crystals maintain their morphology,allowing a quantitative comparison of their properties at both the ensemble and single-crystal level.
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