A cationic metal-organic framework consisting of nanoscale cages: capture, separation, and luminescent probing of Cr(2)O7(2-) through a single-crystal to single-crystal process.

Dichromate capture: A 3D cationic metal-organic framework consisting of distorted octahedral and tetrahedral cages was constructed by using Ag(I) and 4,4'-bis(1,2,4-triazole). The complex exhibits fast exchange, high trapping capacity, and good selectivity for Cr2 O7 (2-) through single-crystal to single-crystal transformation. The complex also features a bluish violet luminescence that is distinctly quenched after Cr2 O7 (2-) exchange.