Interaction of intractable gaseous SO2 with new adsorbent—Metal organic frameworks: M-MOF-74 (M = Co, Ni, Zn).

The nature of adsorption between MOF absorbent and SO 2 remains a challenging issue due to the difficulty in understanding their interaction force and dynamic behavior on molecular level. Herein, a new series of M-MOF-74 (M = Co, Ni, Zn) with high SO 2 adsorption performance were synthesized through an improved solvothermal method. The interaction between M-MOF-74 (M = Co, Ni, Zn) and SO 2 was revealed by combining in-situ infrared spectroscopy and density functional theory (DFT) calculations. It was found that Zn-MOF-74 shows excellent SO 2 uptakes (8.16 mmol g−1), significantly higher than that of Co-MOF (6.11 mmol/g) and Ni-MOF (6.36 mmol/g). These results were consistent with SO 2 binding energies calculated at optimal adsorption sites, which were −11.1 kcal/mol, −12.2 kcal/mol, −18.2 kcal/mol for M-MOF-74 (M = Co, Ni, Zn), respectively. The specific adsorption behavior of Zn-MOF-74 towards SO 2 is attributed to its higher negative attraction of electrostatic potential(∼48.2 kcal/mol)and van der Waals pulling forces (∼−2.6 kcal/mol). The higher interaction force between Zn-MOF-74 and SO 2 was elucidated not only by their strong dominant dispersion interactions, but also by the formation of hydrogen bonding between SO 2 and benzene ring, as demonstrated by independent gradient model (IGM) and infrared analysis. What's more, a unique radial SO 2 movement with high speed of 323 p.m.2/ps, which was much higher than that of traditional molecular sieve (∼240 p.m.2/ps) adsorbent, were observed towards Zn-MOF-74 framework wall. Then the pore size of MOF-74 and SO 2 motion trajectory was analyzed by Molecular Dynamics. This work gives insight into mechanisms on SO 2 adsorption in MOFs. [Display omitted] • Synthesis of M-MOF-74 (M = Co, Ni, Zn) with high SO 2 adsorption performance via an improved solvothermal method. • Zn-MOF-74 shows excellent SO 2 uptakes significantly higher than that of Co-MOF and Ni-MOF. • The adsorption results were consistent with SO 2 binding energies calculated at optimal adsorption sites. • The high interaction force was elucidated by strong dominant dispersion interactions and hydrogen bonding formation. • A unique radial SO 2 movement with high speed which was much higher than that of molecular sieve were observed. [ABSTRACT FROM AUTHOR]