Construction of 2D Zinc(II) MOFs with Tricarboxylate and N-donor Mixed Ligands for Multiresponsive Luminescence Sensors and CO Adsorption

The solvothermal reactions of ZnCl·6HO, benzene-1,3,5-tribenzoic acid (Hbtb), and N-heterocyclic ancillary imidazole (Im) or aminopyrimidine (a mp) ligands led to the creation of two-dimensional (2D) zinc(II) based metal-organic frameworks (MOFs), (MeNH)[Zn(btb)(Im)]·2DMF·3MeOH (1) and (MeNH)[Zn(btb)(amp)]·HO·2DMF·MeOH (2). The btb ligands in 1 and 2 form an anionic 2D layered structure with a (6) honeycomb (hcb) topology by linking to Zn(II) centres through their carboxylate groups. The incorporation of N-heterocyclic auxiliary ligands Im and amp into the hcb nets resulted in the formation of a 2D hydrogen-bonded and covalently pillared bilayer structure featuring two-fold interpenetrating networks. Each of these networks consists of small channels that are occupied by MeNH cations and solvent molecules. Both 1 and 2 emit blue luminescence emissions in the solid state at room temperature and exhibit a great selectivity and sensitivity for the detection of acetone and multiple heavy metal ions including Hg, Cu, Fe, Pb, Cr, and Fe ions. At 1 bar, activated 1 and 2 demonstrate moderate capacities for adsorbing CO at room temperature, with a preference for CO over N. Notably, at higher pressures (up to 20 bar), their activated samples 1 and 2 show a temperature-dependent enhancement of CO uptake while retaining good stability.