Facile Fabrication of a Multifunctional Metal–Organic Framework-based Sensor Exhibiting Exclusive Solvochromic Behaviors toward Ketone Molecules

To
probe the efficient strategy for preparing a multifunctional sensing
material, the facile synthesis strategies and successful examples
are urgently required. Through the utilization of a hexadentate ligand
derived from cyclotriphosphazene, which displays spiral configurations
and multiple connection modes, a novel metal–organic framework
(MOF) was constructed via one-step synthesis from low-cost raw materials.
The presence of multiple interaction sites decorating the helical
channels of the reported MOF gives rise to exclusive solvochromic-sensing
behavior for small ketone molecules such as acetone, acetophenone,
and 2,5-diketohexane. Additionally, the helical structure of a manganese-carboxylate
chain allows for the pore volume not only be available for the adsorption
of large organic molecules but also enables the enantiopure selective
separation of 1-phenylethanol (ee 35.99 %). Furthermore, the structural
analysis of the acetophenone-encapsulated sample allowed the solvochromic
mechanism to be elucidated, which should be ascribed to the strong
hydrogen-bonding interaction between the guest molecules and specific
sites on a host matrix. The experimental results have not only clearly
manifested the vital role of starting materials of MOFs, including
the connection modes and spatial configuration, but also have provided
very valuable insight for the future assembly of novel multifunctional
sensing materials.