The preparation of DyGd-L1L2 MOFs and the luminescent sensing properties for pH value

A series of bimetallic-organic frameworks (MOFs), Dy x Gd 1-x -L 1 L 2 (x=0.005, 0.01, 0.015, 1), have been synthesized via solvent-thermal method using Gd 3+ as the matrix ion, Dy 3+ as the emission center, 1,10-phenanthroline(L 1 ) and 2-aminoterephthalic acid(L 2 ) as organic ligands, DMF and methanol as solvents. The XRD and FT-IR patterns indicated the concentration of Dy 3+ did not change the crystal structure and bonding, and the SEM morphologies demonstrated the MOFs as irregular flake-like particles. The PL spectra revealed two characteristic peaks of Dy 3+ (481 nm and 575 nm) arisen from transition of 4 F 9/2 → 6 H 15/2 and 4 F 9/2 → 6 H 13/2 appeared, with the highest intensity at x=0.01. Notably, the emission intensity of Dy 0.01 Gd 0.99 -L 1 L 2 increased linearly with the increase of pH within a range of 3.4-8.8, and the acidity coefficient (pKa) was calculated as 3.69, implying a good sensing for pH value, combined with a good cyclic stability and anti-interference, which was deduced from protonation/deprotonation with the variation of pH value.