Open-framework transition metal fluorophosphates with one-dimensional antiferromagnetic chains

Abstract Two open frameworks fluorophosphates materials (NH4)2M2F2(PO4)(PO3F)OH (M ​= ​Fe and V) have been synthesized via fluoride-rich hydrothermal routes at 493 ​K. The two isostructural compounds revealed three-dimensional (3D) frameworks, composed of trans-MO4F2, cis-MO4F2, trans-MO2F2(OH)2 octahedra, and PO4, PO3F and NH4 tetrahedra. The anionic backbone of (NH4)2M2F2(PO4)(PO3F)OH consists of a series of parallel zigzag [M2F2O7OH] chains cross-connected with each other, bridged by PO4 tetrahedra within two-dimensional (2D) layer, and bridged by PO3F groups vertical to 2D layer. It generates a three 3D open framework. The XPS spectra revealed the valence of Fe and V are III in the corresponding compounds. The isostructural compounds feature transition metal zigzag chains, which promotes robust antiferromagnetic (AFM) interactions in (NH4)2Fe2F2(PO4)(PO3F)OH in contrast to weak AFM in (NH4)2V2F2(PO4)(PO3F)OH.