Three d10 based metal-organic frameworks constructed from 2-(3′,4′-dicarboxylphenoxy) isophthalic acid: Dual-functional sensors for Cu2+, Fe3+ cations and Aspartic acid

A series of d(10) based metal-organic frameworks (MOFs), namely, [Cd-2(dpc)(biPY)(H2O3)(3)](n) (I), {[Cd-2(dpc)(bib)(H2O)]center dot H2O}(n) (II), {[Cd-2(dpc)(bitb)(1.5)(H2O)(2)]center dot H2O}(n) (III) (H(4)dpc = 2-(3',4'-dicarboxylphenoxY) isophthalic acid, bipy = 4,4'-dipyridyl, bib = 1,4-bis (1-imidazolyl)benzene, bitb = 1,4-bis (imidazol-1-ylmethyl)benzene) have been designed and successfully synthesized using a flexible tetrabasic carboxylic acid along with three ancillary ligands under hydrothermal conditions, which exhibit structural diversities of targeted Cd-MOFs. Single-crystal X-ray diffraction analysis reveals that they contain building units of {CdN1O6} and {CdN1O5} (for I), {CdN1O5} (for II), as well as {CdN2O4} and {CdN5O1} (for In), based on which to assemble microporous three-dimensional (3D) frameworks via covalent bonds and/or hydrogen bonds using multiple coordination modes of H(4)dpc ligand and auxiliary linkers. The solid-state luminescence performances of these Cd-MOFs were investigated at ambient temperature. Furthermore, luminescent sensing responses of to amino acids and metal cations were systematically explored. Notably, I and II may act as potential dual-functional luminescent sensors for Aspartic acid and Cu2+ cations as well as Aspartic acid and Fe3+ cations with high selectivity and sensitivity in aqueous solutions, respectively. The mechanisms of the quenching effect and sensing properties of the as synthesized Cd-MOFs have also been discussed in this report.