Multi-Responsive Luminescent Sensors Based on Two-Dimensional Lanthanide-Metal Organic Frameworks for Highly Selective and Sensitive Detection of Cr(III) and Cr(VI) Ions and Benzaldehyde

Four new isostructural two-dimensional lanthanide(III)metal organic frameworks (MOFs), namely, [Ln(L)(HCOO)(H2O)](n) (Ln = Eu 1, Gd 2, Ho 3, and Tb 4, H2L = 5-((2'-cyano-[1,1'-biphenyl]-4-yl)methoxy)isophthalic acid), with a uninodal {4(4).6(2)}-sql topology have been successfully isolated. Compounds 1 and 4 exhibit excellent applications as luminescent sensors for sensing benzaldehyde in methanol and Cr3+, CrO42-, and Cr2O72- in water with high sensitivity and selectivity based on luminescence quenching effects. Interestingly, 1 and 4 display excellent recyclable behaviors and can be recycled at least five times for sensing benzaldehyde, Cr(III) and Cr(VI) ions. These two compounds are the first multifunctional Ln-MOFs sensors for detecting benzaldehyde, Cr(III) and Cr(VI) ions, simultaneously. Therefore, these two materials may be excellent multifunctional recyclable luminescent sensors.