Two new metal phosphite-oxalates, CN3H6·Co(H2PO3)(C2O4) (1) and (CN3H6)2·Mn2.5(HPO3)(C2O4)2.5(H2O)·H2O (2), have been prepared under solvent-free conditions. The two open-framework compounds have diamondoid and pillared-layered structures, respectively. Their photoluminescence and magnetic properties were also investigated.