Selective Identification and Encapsulation of Biohazardous m-Xylene among a Pool of Its Other Constitutional C8 Alkyl Isomers by Luminescent d10 MOFs: A Combined Theoretical and Experimental Study.

Separation of C8 alkyl-aromatics (o-xylene, m-xylene, and p-xylene) remains one of the most challenging tasks to date due to their similar physical and chemical properties. Cd2+- and Zn2+-based luminescent metal-organic frameworks (MOFs) have been synthesized for the selective identification of m-xylene in a pool of other isomers by fluorometric methods. Inhibition of the photoinduced electron transfer process is the prime reason for fluorescence enhancement, owing to the comparable molecular orbital energies for m-xylene in comparison with o- and p-xylene. Density functional theory calculations signify that the extraordinary selectivity is mainly due to the high dipole moment of m-xylene that might enhance the ring current, leading to a strong π-π interaction with the MOF's co-ligand. As a practical application, fluorometric sensing could be used for the estimation of m-xylene in different solvent media. Moreover, X-ray structural analysis reveals that the Zn2+-MOF can encapsulate m-xylene selectively within its framework among other constitutional isomers, which also emphasizes its capability for practical implementation.