Analysis by synchrotron X-ray scattering of the kinetics of formation of an Fe-based metal-organic framework with high CO2 adsorption

Abstract

Understanding the mechanism of assembly and function of metal-organic frameworks (MOFs) is important for the development of practical materials. Herein, we report a time-resolved diffraction analysis of the kinetics of formation of a robust MOF, MFM-300(Fe), which shows high adsorption capacity for CO2 (9.55 mmol g−1 at 293 K and 20 bar). Applying the Avrami-Erofe’ev and the two-step kinetic Finke-Watzky models to in situ high-energy synchrotron X-ray powder diffraction data obtained during the synthesis of MFM-300(Fe) enables determination of the overall activation energy of formation (50.9 kJ mol−1), the average energy of nucleation (56.7 kJ mol−1), and the average energy of autocatalytic growth (50.7 kJ mol−1). The synthesis of MFM-300(Fe) has been scaled up 1000-fold, enabling the successful breakthrough separations of the CO2/N2 mixture in a packed-bed with a selectivity for CO2/N2 of 21.6. This study gives an overall understanding for the intrinsic behaviors of this MOF system, and we have determined directly the binding domains and dynamics for adsorbed CO2 molecules within the pores of MFM-300(Fe).

Tunable Strategies Involving Flexibility and Angularity of Dual Linkers for a 3D Metal–Organic Framework Capable of Multimedia Iodine Capture

“… − ,,− An apparent weight loss of 42.6% (excluding the lattice solvent molecules) in the temperature range of 30–200 °C shows that there are four iodine molecules captured per formula unit of 1 (Figure S17). The results are in corroboration with the fact that the incorporation of heteroatoms and π electron-rich aromatic systems in solid sorbents is an efficient way to increase the sorption capacity of the system. , The presence of immensely available π cloud of the pyridyl, phenyl, and oxadiazole rings allow the iodine molecules to be channeled and be restricted in regulated limits in the pores of 1 causing n → σ* charge transfer. , Similar to adsorption of polar gases where intermolecular interactions between the guests become predominant at higher loadings, iodine molecules undergo self-aggregation due to confinement in the narrow channels of the host molecule. , …”

“…23,58 Similar to adsorption of polar gases where intermolecular interactions between the guests become predominant at higher loadings, iodine molecules undergo self-aggregation due to confinement in the narrow channels of the host molecule. 60,61 Iodine Removal from Organic Solution Phase. In addition to vapor sorption, iodine removal from cyclohexane solution is also studied under ambient conditions.…”

In Situ Investigation of Multicomponent MOF Crystallization during Rapid Continuous Flow Synthesis

“…In addition to monitoring phase transitions, the kinetics of nucleation and growth have been obtained for single-component MOFs such as Cu-BTC, ZIF-8, Zr-Fum, and MIL-53­(Fe). ,− The growth of these MOFs has been modeled using Avrami–Erofe’ev as a base model and also either the Gualtieri or Finke–Watzky model. − These models describe the formation mechanisms, with previous findings showing that the formation mechanism of these MOFs typically varies between nucleation rate limited or phase boundary (surface reaction) rate limited …”