Copper-containing porphyrin aluminum MOF, sorption of diethyl sulfide in air, its kinetics, mechanism, and the stoichiometric adsorption complex

Abstract

Metal-organic frameworks (MOFs) are 3-dimensional coordination polymers which contain metals and organic linkers. MOFs are of strong interest in the fields of separation, catalysis, chemo-sensing, and pollution remediation. MOFs are highly desired, which have complex and controlled composition, structure and functional properties. Here, we report the copper porphyrin aluminum MOF (actAl-MOF-TCPPCu) denoted compound 4, and mechanistic and kinetic studies of adsorption of volatile organic sulfur compound, diethyl sulfide (DES) by it. The characterization is conducted by qualitative and quantitative methods, structural analysis with the Rietveld crystal lattice refinement, and complementary microscopy and spectroscopy. Then a comprehensive study of mechanism and kinetics of DES sorption is presented, under the dynamic conditions in the flow of air. The latter is conducted by a novel method of in-situ time-dependent ATR-FTIR spectroscopy in the controlled environment. The binding sites of DES include the µ(O–H), the COO⁻ group, phenyl and pyrrole groups and they are ranked by the strengths of bonding. The kinetics of sorption obeys the Langmuir model of the pseudo-first order rate law with effective rate constant k_eff = 0.95 ± 0.05 min^− 1. Moreover, the linear dependence of kinetic rate constant on concentration of DES suggests that the sorption is diffusion limited. The sorption of DES in the static equilibrium conditions results in the binary stochiometric adsorption complex with formula (Al-MOF-TCPPCu)₂(DES)₇. Finally, a facile regeneration of the adsorption complex was achieved, without using chemicals. The copper-containing porphyrin aluminum MOF and related materials are promising for the removal of volatile organic sulfur compounds from air.