New three-dimensional open-framework zinc phosphite and manganese phosphite-oxalate, H 2 dah·Zn 3 (HPO 3 ) 4 (1) and H 2 dab·Mn 2 (HPO 3 ) 2 (C 2 O 4 )(H 2 O) 2 (2), were prepared in a flux of phosphorous acid without the addition of water as a solvent (dah=1,7-diaminoheptane, dab=1,4-diaminobutane). Compound 1 is constructed from strictly alternating ZnO 4 tetrahedra and HPO 3 pseudo pyramids, and has zigzag 12-ring channels running along the [001] direction. Compound 2 consists of neutral manganese phosphites layers, which are pillared by oxalate ligands to form a three-dimensional hybrid framework with 12-ring channels running along the [010] direction. Magnetic susceptibility measurements demonstrate the existence of antiferromagnetic interaction in 2. Crystal data: 1, orthorhombic, Pbcn, a=9.9096(8)Å, b=15.6780(6)Å, c=13.8022(6)Å, V=2144.3(2)Å 3 , Z=4; 2, monoclinic, P2 1 /n, a=5.616(3)Å, b=15.431(3)Å, c=9.445(3)Å, β=91.72(2)°, V=818.2(5)Å 3 , Z=2.