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Fast and Selective Heavy Metal Removal by a Novel Metal‐Organic Framework Designed with In‐Situ Ligand Building Block Fabrication Bearing Free Nitrogen
Author(s) -
Rouhani Farzaneh,
Morsali Ali
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201706016
Subject(s) - adsorption , metal organic framework , aqueous solution , chemistry , ligand (biochemistry) , metal ions in aqueous solution , nitrogen , supramolecular chemistry , metal , langmuir adsorption model , fourier transform infrared spectroscopy , inorganic chemistry , nuclear chemistry , chemical engineering , organic chemistry , molecule , biochemistry , receptor , engineering
Fast and effective adsorbents for the selective removal of Hg II and Pb II ions were prepared by the reaction of Zn(NO 3 ) 2 ⋅ 6H 2 O, H 2 BDC, and N 1 ,N 2 ‐bis(pyridin‐4‐ylmethylene) ethane‐1,2‐diamine (L) that yields an unprecedented two‐dimensional layer‐based supramolecular framework, {Zn(BDC)(L*)} ⋅ DMF (TMU‐40), by solvothermal reaction. The formation of this framework involved an in situ C=C coupling of L to L* [L*=5,6‐di(pyridin‐4‐yl)‐1,2,3,4‐tetrahydropyrazine]. As L* contains free nitrogen atoms, direct reaction of L* and metals led to metallated products. Post‐synthetic modification of this novel MOF (TMU‐40) with H 2 O 2 gives a new framework (O‐TMU‐40) by same structure and different ligand, which also bears free nitrogen atoms. FTIR spectra, TGA analysis, X‐ray diffraction, Zeta Potential analysis and 1 H NMR spectroscopy were used to characterize the prepared frameworks. The TMU‐40 and O‐TMU‐40 frameworks were used for heavy‐metal removal from aqueous solutions. Maximum adsorption values of 269 mg g −1 for Hg II with TMU‐40 and 215 mg g −1 for Pb II with O‐TMU‐40 were achieved in 10 min at 298 Kwithout changes in the pH of the adsorption medium with pseudo‐second order kinetics based on the Langmuir model. The extremely fast kinetics of TMU‐40 means this adsorbent can reduce heavily contaminated water containing Hg II concentrations of 40 ppm down to the acceptable limit of 2 ppb.