Three Cd(II) MOFs with Different Functional Groups: Selective CO₂ Capture and Metal Ions Detection

Abstract

Three Cd(II) iso-frameworks {[Cd(BIPA)(IPA)]·DMF} _n (1), {[Cd(BIPA)(HIPA)]·DMF} _n (2), and {[Cd(BIPA)(NIPA)]·2H₂O} _n (3) were synthesized from the self-assembly of the BIPA ligand (BIPA = bis(4-(1 H-imidazol-1-yl)phenyl)amine) and different carboxylic ligands (H₂IPA = isophthalic acid, H₂HIPA = 5-hydroxyisophthalic acid, H₂NIPA = 5-nitroisophthalic acid) with Cd(II), which have amino groups, amino and phenolic hydroxyl groups, and amino and nitro groups, respectively. Both 1 and 2 exhibit CO₂ uptakes of more than 20 wt %, indicating that amino and phenolic hydroxyl functionalized groups are beneficial to CO₂ adsorption. Their applications and mechanisms in detecting metal ions were researched. The results exhibit that 1 and 2 are dual-responsive photoluminescent sensors for Hg²⁺ and Pb²⁺ ions with low detection concentration and high quenching constant. Besides, like most MOFs, 3 can detect a trace quantity of Fe³⁺ and Cu²⁺.