Synthesis, spectroscopic study and carbofuran adsorption of mixed metal (Co, Cu)@Ca-BTC frameworks aimed at wastewater cleaning

Abstract

The extensive use of insecticides raises a great risk to humans because these compounds are human carcinogens and their agricultural application causes contamination of natural free water. One of the most applied insecticide is carbofuran, and the present study aims at removing it from water using novel mixed metal–metal-organic frameworks (M−MOFs) based on Ca-benzene-1,3,5-tricarboxylic acid (Ca-BTC). Different “guest” metal ions (M = Mn, Ni, Co, Cu; each at 20 %) and Ca (at 80 %) were mixed together with the organic linker BTC to produce Ca-M−BTC. Different geometrical shapes of Ca-M−BTC were observed depending on the type of the added “guest” metal ion. The EPR spectrum of both Ca-Cu-BTC and Ca-Co-BTC shows a doublet peak with line-broadening at g_// = 2.34 and a broad peak at g ∼ 2.1, respectively, and the narrow peak provided information about the chelating atoms of the paramagnetic Cu²⁺ atom. Carbofuran adsorption follows the second order model and a Langmuir isotherm. The adsorption capacity of carbofuran reached 627.26 and 736.31 mg/g onto Ca-Co-BTC and Ca-Cu-BTC, respectively. Efficient carbofuran adsorption on these Ca-M−BTCs, hence removal from water, can be proceeded via both of physical deposition in pores and chemical interaction via H-bonding, coordination and π – π interaction.