The divalent and trivalent metal silicates [1], carboxylates [2–4]
and phosphates [5,6] constituted the major families of inorganic
framework compounds in the past few decades. And in recent
studies, the synthesis and properties of some new inorganic
open-architecture compounds have been widely investigated
(formed by other oxyanions such as selenates [7], sulfates [8]
and selenites [9]). Thus, a variety of new layered frameworks of
oxyanion with the kagome structure have been prepared and characterized