Patent ID: 7973109

Claim:
A crosslinked type layered metal phosphonate compound in which (a) the crosslinked type layered metal phosphonate compound has a two dimensional layered structure in which metal oxide octahedrons having a hexacoordinate metal atom as a central atom (M) and phosphonic acid tetrahedrons are connected by sharing oxygen atoms, (b) the crosslinked type layered metal phosphonate compound contains at least one organic diphosphonic acid ingredient in which both ends thereof are connected respectively with different hexacoordinate metal atoms in different layered structures by way of at least one P—O-M bond, (c) the crosslinked type layered metal phosphonate compound contains at least one monophosphonic acid ingredient that is bonded with a different hexacoordinate metal atom in the layered structure by way of at least one P—O-M bond, (d) one of the organic diphosphonic acid ingredient and the monophosphonic acid ingredient has a sulfonic group or a group that can be converted into the sulfonic group and the rest of them has no such group, (e) the average molecular cross sectional area for the substituent of the organic diphosphonic acid ingredient and the monophosphonic acid ingredient contained in the crosslinked type layered metal phosphonate compound is equal with or less than the free area of one surface phosphonic acid of the two dimensional layered structure, and (f) the crosslinked type layered metal phosphonate compound does not contain a fluorine atom bonded with the central atom (M).