Low-Temperature Synthesis of Metal–Organic Coordination Polymers Based on Oxo-centered Iron Complexes: Magnetic and Adsorption Properties

A low-temperature approach is described for preparing mesoporous metal–organic frameworks using nontoxic solvents and pre-synthesized polynuclear iron complexes as secondary building units. The obtained compounds are characterized via IR and Mössbauer spectroscopy, X-ray powder diffraction analysis, thermogravimetric analysis, and differential scanning calorimetry. The specific surface of the obtained compounds and their adsorption capacity for organic dyes methylene blue and Congo red are determined. Particular attention is given to dependences M ( T ) and M ( H ) of the magnetic moment of the obtained samples on temperature and strength of the magnetic field, respectively. The dyes’ adsorption characteristics and efficiency of sorption are determined by varying such factors as period of contact, amount of adsorbent, and temperature. The removal of dye at a concentration above 90% is observed as early as 20–30 min after the beginning of adsorption. Langmuir and Freundlich isotherms are used to describe the experimental data. It is shown that the process of adsorption at the initial concentration of the dye is described most accurately by the Langmuir adsorption isotherm. The rate constants of adsorption are calculated using pseudo-second order kinetic equations.