An uncommon 3D 3,3,4,8-c Cd(ii) metal–organic framework for highly efficient luminescent sensing and organic dye adsorption: experimental and theoretical insight

Abstract

A new Cd(II) based metal–organic framework (MOF), having formula {(CH₃)₂NH₂)₆[Cd₅(L)₄]·H₂O·3DMF}_n (1), has been synthesized based on a rigid tetracarboxylate ligand of terphenyl-3,3′′,5,5′′-tetracarboxylic acid (H₄L). 1 shows a complicated 3D tetranodal 3,3,4,8-c network with uncoordinated –COO⁻ groups. The highly selective luminescent sensing of 2,4-dinitrophenol (2,4-DNP), 2,4,6-trinitrophenol (TNP) and ferric ions was studied for 1 through the alleviation in its fluorescence intensity. The detection limit of 2,4-DNP was found to be 0.84 ppm, which is 20 times higher than that of 1,3,5-trimethylbenzene, demonstrating greater and selective quenching ability. The possible mechanism associated with the decrease in fluorescence intensity of 1 in the presence of nitroaromatics (NACs) has been addressed by theoretical calculations. Furthermore, 1 displays excellent capacity to adsorb methylene blue (MB) with high selectivity, and it maintains an almost identical adsorption performance after being recycled five times.