Site‐Selective Functionalization of Periodic Mesoporous Organosilica (PMO) with Macrocyclic Host for Specific and Reversible Recognition of Heavy Metal

A novel kind of macrocyclic‐host‐functionalized periodic mesoporous organosilica (PMO) with excellent and reversible recognition of Pb^II was developed. The macrocyclic host molecule cis‐dicyclohexano18]crown‐6, with strong affinity to Pb^II, was carefully modified as a bridged precursor to build the PMO material. To break down the limit of the functionalization degree for PMOs incorporated with large‐sized moieties, a site‐selective post‐functionalization method was proposed to further decorate the external surface of the PMO material. The selective recognition ability of the upgraded PMO material towards Pb^II was remarkably enhanced without destroying the mesoporous ordering. Solid‐state ¹³C and ²⁹Si NMR spectroscopy, X‐ray photoelectron spectroscopy (XPS), XRD, TEM, and nitrogen adsorption–desorption isotherm measurements were utilized for a full characterization of the structure, micromorphology, and surface properties. Reversible binding of Pb^II was realized in the binding–elution cycle experiments. The mechanism of the supramolecular interaction between the macrocyclic host and metal ion was discussed. The synthetic strategy can be considered a general way to optimize the properties of PMOs as binding materials for practical use while preserving the mesostructure.