Copper Oxygen Cluster-Based Metal–Organic Framework for Logical Fe3+ and Cr3+ Sensing and Chemical Fixation of CO2

Abstract

Metal–organic frameworks (MOFs) exhibit attractive performance in fields such as luminescence sensors and catalysis. We here developed a new MOF ({Cu₂(DPQ)₂(OBPBI)}_n), briefly named Cu-MOF, which has been facilely obtained through the self-assembly of 4, 4′-(quinoxaline-2, 3-diyl)dibenzoic acid (H₂DPQ), 1, 1′-[oxybis(4, 1-phenylene)]bis(1H-imidazole) (OBPBI), and CuCl₂·2H₂O under solvothermal conditions. Cu-MOF contains a paddle-wheel and binuclear copper oxygen cluster unit and forms a 2, 2, 6-connected two-dimensional (2D) net with the point symbol of {4²·8⁸·12⁵}{4}₂{8}. Luminescence investigations indicate that Cu-MOF has a selective fluorescent response to Fe³⁺ and Cr³⁺ ions in water, with detection limits low to 10^–8 M, at least three times reusability, and a wide pH applicable scope. A combined logic gate INHIBIT has been built based on the different signal inputs of Fe³⁺ and Cr³⁺ ions and emission intensity signal outputs, providing great potential for distinguishing Fe³⁺ and Cr³⁺ ions. Moreover, Cu-MOF has been successfully applied for the catalytical conversion of CO₂ to cyclic carbonates under solvent-free and mild conditions (0.1 mol % Cu-MOF, 3 mol % TBAB, 1 atm of CO₂, 15 h, 85 °C), with up to 98% yield, 99% selectivity, and three times reusability.