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 (Mn < Fe < Co < Ni < Cu > Zn) 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.

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 (Mn < Fe < Co < Ni < Cu > Zn) 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.

Predicting crystal morphologies …… is challenging because of the many factors influencing their growth. Dan Oron, Michal Lahav, Milko E. van der Boom, and co-workers demonstrate in their Research Article (e202205238) how metal cation exchange in metal-organic frameworks (MOFs) results in a series of chiral crystals having a similar morphology, packing, and a rare space group (P622). The fact that the crystals maintain their morphology facilitates a quantitative comparison of their optical and magnetic properties. The metal cation exchange is likely to be mediated by differently sized nanochannels.

Crystals are among the most challenging materials to design, both at the molecular and macroscopic levels. We show here that metal-organic frameworks, based on tetrahedral pyridyl ligands, can be used as a morpho-logical and structural mold to form a series of other isostructural crystals having different metal ions. The cati-on exchange is versatile, based on the use of diverse first-row metals; it occurs with retention of the morpholo-gy. Different morphologies were obtained by a direct reaction between the ligand and metal salts. An iterative crystal-to-crystal conversion has also been demonstrated by two consecutive cation exchange processes. The primary manganese-based crystals have a complex connectivity characterized by a rare space group (P622). The molecular structure generates two types of homochiral channels that span longitudinally the entire hex-agonal prism. These channels mediate the cation exchange, as indicated by energy-dispersive X-ray spectros-copy combined with scanning electron microscopy measurements on microtome-sectioned crystals. The occur-rence of the observed cation exchange is in excellent agreement with the Irving-Williams series (Mn < Fe < Co < Ni < Cu > Zn) that are associated with the relative stability of the resulting coordination nodes. The overall approach allows for the predictability of the structural properties of rare metal-organic frameworks based on tetrahedral pyridyl ligands at different hierarchies: from elemental composition, molecular packing, and mor-phology to the bulk properties.

Crystals are among the most challenging materials to design, both at the molecular and macroscopic levels. We show here that metal-organic frameworks, based on tetrahedral pyridyl ligands, can be used as a morpho-logical and structural mold to form a series of other isostructural crystals having different metal ions. The cati-on exchange is versatile, based on the use of diverse first-row metals; it occurs with retention of the morpholo-gy. Different morphologies were obtained by a direct reaction between the ligand and metal salts. An iterative crystal-to-crystal conversion has also been demonstrated by two consecutive cation exchange processes. The primary manganese-based crystals have a complex connectivity characterized by a rare space group (P622). The molecular structure generates two types of homochiral channels that span longitudinally the entire hex-agonal prism. These channels mediate the cation exchange, as indicated by energy-dispersive X-ray spectros-copy combined with scanning electron microscopy measurements on microtome-sectioned crystals. The occur-rence of the observed cation exchange is in excellent agreement with the Irving-Williams series (Mn < Fe < Co < Ni < Cu > Zn) that are associated with the relative stability of the resulting coordination nodes. The overall approach allows for the predictability of the structural properties of rare metal-organic frameworks based on tetrahedral pyridyl ligands at different hierarchies: from elemental composition, molecular packing, and mor-phology to the bulk properties.