A luminescent zinc(ii) coordination polymer with unusual (3,4,4)-coordinated self-catenated 3D network for selective detection of nitroaromatics and ferric and chromate ions: a versatile luminescent sensor

Abstract

A zinc(II) coordination polymer {[Zn₃(mtrb)₃(btc)₂]·3H₂O}_n (1) was synthesized and characterized (mtrb = 1,3-bis(1,2,4-triazole-4-ylmethyl)benzene, btc = 1,3,5-benzenetricarboxylate). The polymer 1 shows an unusual (3,4,4)-coordinated self-catenated 3D network with the point symbol of {6³}₂{6²·8²·10²}{6⁴·8²}₂. The polymer 1 is the first luminescent sensor for the detection of 2-amino-4-nitrophenol (ANP). The polymer 1 is also a good luminescence sensor for detection of TNP, 2,4-DNP, 4-NP, ANP and 2-NP in MeOH, particularly for TNP. The order of detection efficiency is TNP > 2,4-DNP > 4-NP > ANP > 2-NP. The polymer 1 also exhibits high sensitivity and selectivity as a luminescence sensor for the detection of Fe³⁺, Cr₂O₇²⁻ and CrO₄²⁻ in aqueous solution. Our experiments showed that the presence of interfering ions had no significant effect on the sensing of Fe³⁺, Cr₂O₇²⁻ or CrO₄²⁻ ions. The detection limits for TNP, ANP, Fe³⁺, Cr₂O₇²⁻ and CrO₄²⁻ are 0.22 μM, 4.12 μM, 1.78 μM, 2.83 μM, and 4.52 μM, respectively. The luminescence sensor is stable and can be recycled for detection at least five times. The possible quenching mechanisms are discussed. The polymer 1 is also an effective photocatalyst for degradation of methylene blue (MB) under visible or UV light irradiation.