Macroscopic Magnetic Anisotropy Induced by the Combined Control of Size, Shape and Organization of NiFe Prussian Blue Analog Nanoparticles in an Ordered Mesoporous Silica Monolith

Integration of coordination polymers and metal–organic frameworks into real applications requires a processing step at the nanoscale. However, their synthesis in the form of nanoparticles with controlled size, shape and organization remains a challenge faced by diverse scientific communities. Ordered mesoporous silica monolith with 2D-hexagonal structure of the mesopores is used to form ferromagnetic NiFe Prussian blue analog (PBA) nanoparticles with anisotropic shape. The PBA nanowires formed within the nanochannels of the monolith are made of single chains of nanocrystals. Furthermore, when using an ordered mesoporous silica monolith instead of the more frequently used mesoporous powders a parallel organization of the pores is achieved over whole macroscopic fragments of the monolith. A 1×1×1 mm3 fragment of monolith exhibits a remarkably strong anisotropy in its magnetic properties, arising from unprecedented magnetic dipolar interaction along the chains of coordination nanocrystals, which is spread to the macroscopic scale thanks to the long-range organization of the pores. As various confined chemistries can be developed within the ordered porosity of such monolith, this tool opens up new opportunities for the development of original nanostructured materials exhibiting anisotropy in their properties at the macroscopic scale.