Developing a Bifunctional Copper-Organic Framework for Fluorescence Turn-on Hg²⁺ Sensing and Catalyzing CO₂ Cycloaddition Reaction

Abstract

Metal−organic frameworks attract great attention because they show great potential for applications such as catalysis and luminescence sensing. Herein, a novel copper−organic framework, [Cu 2.5 (OH)(nia) 2 (Bibt) 1.5 ] n , known as CuBN, was hydrothermally prepared based on the self-assembly of 4,7-bis(1H-imidazole-1-yl) benzo-[2,1,3]thiadiazole (Bibt), 5-(1,8naphthalimido)-isophthalic acid (H 2 nia), and CuCl 2 •2H 2 O. CuBN exhibited a 4, 8-connected sqc 3D porous framework with a binuclear copper oxygen cluster unit and the point symbol of {3 4 4 8 5 12 6 4 }{3 2 4 2 5 2 }. CuBN can work as an efficient luminescent sensor for Hg 2+ via a turn-on fluorescence change. Fluorescent data shows that CuBN has high selectivity to Hg 2+ among various metal ions, and the detection limit is low, down to 9.52 nM. The turn-on sensing behavior can be mainly attributed to the Hg 2+promoted framework collapsing and subsequent binding to the ligand Bibt. In addition, CuBN exhibits the capability of promoting the chemical fixation of CO 2 to cyclic carbonates under mild conditions (0.1 mol % catalyst loading, 2 mol % TBAB, 1 atm of CO 2 , 24 h, 80 °C and without solvent) with up to 97% yield and good reusability.