Dye-encapsulated nanocage-based metal-organic frameworks as luminescent dual-emitting sensors for selective detection of inorganic ions

A novel manganese-based metal-organic framework (Mn-MOF) with nanocage has been successfully synthesized by pore space partition (PSP) strategy. Benefiting from the ternary inorganic secondary building units (SBUs) of mononuclear, trinuclear, and rare tetranuclear bi-paddlewheel, the material possesses good stability and abundant open metal sites (OMSs). As far as the organic SBU, the uncoordinated pyridine groups promote the formation of Lewis basic sites (LBSs). The multiple SBUs construct the overall framework with three types of cages which exhibits novel topology. Furthermore, the anionic framework provides the impetus to encapsulate cationic dyes, which facilitates the construction of dual-emitting luminescent RhB@Mn-MOF material with self-calibrating sensing abilities. The composite material features prominent selective detection performance to Fe (III), which is obviously superior to the parent material. Additionally, a Zn-MOF with similar structure to Mn-MOF shows selective detection ability to Cu (II) and P2R@Zn-MOF prepared by dye-encapsulated has enhanced performance. However, the Mn-based materials prepared by PSP provide appropriate cage and more active sites enable them obtain better detection ability. Therefore, the synergistic effect of PSP and dye-encapsulated strategy is beneficial to improve the selective detection performance of the materials to inorganic ions.