Following the strategy of using polyfunctional phosphonic acids for the synthesis of open-framework metal phosphonates, 3-amino-1-hydroxypropylidene-1, 1-bisphosphonic acid was used in the synthesis of a new calcium phosphonate. The compound, calcium-3-amino-1-hydroxypropylidene-1,1-bisphosphonic acid [Ca 0.5{(H 3N +CH 2CH 2)C(OH)- (PO 3H -)(PO 2H -)} 2].H 2O (1) is a three-dimensional framework prepared by nonhydrothermal synthesis route.

The asymmetric unit contains one independent Ca atoms, two chelating and bridging phosphonic ligands and one lattice water molecule. The structure of 1 is built up from CaO 6 polyhedra forming CaO chains connected to a three-dimensional metaloxygen-metal framework with ammonium propyl groups pointing into the space between these layers. There are empty pore within the layers along the 'c' direction. 

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