The open-framework iron phosphate IIIII21.543FeFe(PO) was hydrothermally synthesized and characterized by elemental analysis, IR, EPR, XPS and single crystal X-ray diffraction analysis. The title compound crystallized in the triclinic, space group P1with a=0.64724(4) nm, b=0.79651(6) nm, c=0.94229(5) nm, =104.447(2)? =108.919(4)? =101.741(4)? V=0.42302(5) nm3, Z=1 and R1 (wR2)=0.0307 (0.0793). Crystal data were collected on a Rigaku R-AXIS RAPID IP diffractometer with Mo K?(=0.071073 nm) at 293(2) K in the range of 2.43埃迹?7.46? The structure of 1 consists of 19 non-hydrogen atoms including three and a half crystallographically in-dependent Fe and three P atoms. Fe(1) connects its symmetrical Fe(1A) through bridging oxygen forming a dimer and the dimers are connected by Fe(4) forming an infinite staircase-like chain. Fe(2) and Fe(3) connect the infinite chains into a layer with bridging oxygen. Layers are interconnected via Fe(4) forming the six-membered and eight-membered channel systems. The open-framework iron phosphate IIIII21.543FeFe (PO) was hydrothermally synthesized and characterized by elemental analysis, IR, EPR, XPS and single crystal X-ray diffraction analysis. The title compound crystallized in the triclinic, space group P1with a = 0.64724 (4) = 108.919 (4)? = 101.741 (4)? V = 0.42302 (5) nm3, Z = 1 and R1 (wR2) = 0.0307 (0.0793). Crystal data were collected on a Rigaku R-AXIS RAPID IP diffractometer with Mo K? (= 0.071073 nm) at 293 (2) K in the range of 2.43 of 1 consisting of 19 non-hydrogen atoms including three and a half crystallographically in-dependent Fe and three P atoms. Fe (1) connects its symmetrical Fe (1A) through bridging oxygen forming a dimer and the dimers are connected by Fe (4 Fe (2) and Fe (3) connect the infinite chains into a layer with bridging oxygen. Layers are interconnected via Fe (4) forming the six-membered and eight-membered channels ystems.