Two-Dimensional Lanthanide Metal-Organic Frameworks As a Platform for Sensing Pollutant and Nitrophenols Reduction.

The discharge of harmful and toxicpollutants in water is destroyingthe ecosystem balance and human being health at an alarming rate.Therefore, the detection and removal of water pollutants by usingstable and efficient materials are significant but challenging. Herein,three novel lanthanide metal-organic frameworks (Ln-MOFs),[La(L)(DMF)(2)(H2O)(2)]& BULL;H2O (LCUH-104), [Nd(L)(DMF)(2)(H2O)(2)]& BULL;H2O (LCUH-105), and [Pr(L)(DMF)(2)(H2O)(2)]& BULL;H2O (LCUH-106) [H3L = 5-(4-(tetrazol-5-yl)phenyl)isophthalic acid (H(3)TZI)] were solvothermally constructed and structurally characterized.In the three Ln-MOFs, dinuclear metallic clusters {Ln(2)}were connected by deprotonated tetrazol-containing dicarboxylate TZI(3-) to obtain a 2D layered framework with a point symbolof {4(2)& BULL;8(4)}& BULL;{4(6)}. Theirexcellent chemical and thermal stabilities were beneficial to carryout fluorescence sensing and achieve the catalytic nitrophenols (NPs)reduction. Especially, the incorporation of the nitrogen-rich tetrazolering into their 2D layered frameworks enables the fabrication of Pdnanocatalysts (Pd NPs@LCUH-104/105/106) and have dramaticallyenhanced catalytic activity by using the unique metal-supportinteractions between three Ln-MOFs and the encapsulating palladiumnanoparticles (Pd NPs). Specifically, the reduction of NPs (2-NP,3-NP, and 4-NP) in aqueous solution by Pd NPs@LCUH-104 exhibits exceptional conversion efficiency, remarkable rate constants(k), and outstanding cycling stability. The catalyticrate of Pd NPs@LCUH-104 for 4-NP is nearly 8.5 timesmore than that of Pd/C (wt 5%) and its turnover frequency value is0.051 s(-1), which indicate its excellent catalyticactivity. Meanwhile, LCUH-105, as a multifunctional fluorescencesensor, exhibited excellent fluorescence detection of norfloxacin(NFX) (turn on) and Cr2O7 (2-) (turn off) with high selectivity and sensitivity at a low concentration,and the corresponding fluorescence enhancement/quenching mechanismhas also been systematically investigated through various detectionmeans and theoretical calculations. Threenovel two-dimensional Ln-MOFs (LCUH-104/105/106) havebeen successfully obtained. The nitrogen-rich ligands andtwo-dimensional layered structures make them become excellent carriersfor Pd nanoparticles and finally obtained Pd@LCUH-104/105/106, which can rapidly and efficiently catalyze the reduction of nitrophenols.Meanwhile, fluorescence sensing tests confirmed that LCUH-104/105/106 is a reliable multifunctional fluorescence sensor with excellentselectivity and high sensitivity for the low concentration of norfloxacin(turn on) and Cr2O7 (2-) (turnoff).