Two nanocage anionic metal-organic frameworks with rht topology and {[M(H2O)6]6}(12+) charge aggregation for rapid and selective adsorption of cationic dyes.

Two rht anionic metal-organic frameworks were synthesized. There are six [M(H2O)6](2+) ions held together by a super-strong H-bond and arranged in a regular octahedron in each medium cage. Dye adsorption studies revealed a rapid and selective adsorption of cationic dyes and the adsorbed dyes can be released in saturated NaCl aqueous solution.