A stable nitrogen-rich zinc-based metal organic framework to investigate the structural similarity effect on the sorption efficiency of nitrogen-containing compounds

Abstract

A stable porous zinc-based metal organic framework (MOF) containing nitrogen-rich bis-tetrazolate ligand was synthesized to study the role of similar structures concerning both extractive phase and the desired solutes to achieve greater sorption efficiency. With implementing a dispersive micro-solid phase extraction (d-µ-SPE) methodology, the sorption capability and influencing structural parameters i.e., porosity, surface area and interactions types were investigated for the synthesized zinc-bis-tetrazolate (ZnBT) MOF and compared with some synthesized sorbents such as MIL-101, MIL-101-NH2, cadmium naphthalene dicarboxylic acid dimethyl formamide [Cd(NDC)(DMF)], polyaniline and LiChrolut® EN. The sorption trends for triazines, as nitrogen-containing analytes, and benzene homologs, as nitrogen-free compounds, were evaluated. Accordingly, the synthesized ZnBT nanostructure was significantly dominant for the isolation of triazines. Moreover, the observed moderate sorption efficiency of nitrogen-rich MOF toward BTEX verifies the significant role of similar nitrogen-rich structure between MOF and triazines. Eventually, ZnBT was employed as the desired extractive phase for d-µ-SPE of triazines from environmental water samples followed by gas chromatography-mass spectrometric quantification. Under the optimized conditions, limits of detection (S/N = 3) and limits of quantification (S/N = 10) were in the ranges of 2–10 and 6–30 ng L−1, respectively. Also, the linear dynamic range (6–1000 ng L−1) and intra-day (3.3–5.2%) and inter-day (5.5–6.8%) relative standard deviations were comparable with other relevant reports. Among the selected triazines, a quantity of 51 ng L−1 of atrazine was quantified in the paddy water sample B. The obtained relative recovery values of 89–98% at 50 and 500 ng L−1 levels, confirmed the insignificant matrix effect.