title: Tracking the evolution and differences between guest-induced phases of Ga-MIL-53 via ultra-wideline69/71Ga solid-state NMR spectroscopy.
abstract: Ga-MIL-53 is a metal-organic framework (MOF) that exhibits a "breathing effect," in which the pore size and overall MOF topology can be influenced by temperature, pressure, and host-guest interactions. The phase control afforded by this flexible framework renders Ga-MIL-53 a promising material for guest storage and sensing applications. In this work, the structure and behavior of four Ga-MIL-53 phases (as, ht, enp and lt), along with CO2adsorbed within Ga-MIL-53 at various loading levels, has been investigated using69/71Ga solid-state NMR (SSNMR) experiments at 21.1T and 9.4T.69/71Ga SSNMR spectra are observed to be very sensitive to distortions in the octahedral GaO6secondary building units within Ga-MIL-53; by extension, Ga NMR parameters are indicative of the particular crystallographic phase of Ga-MIL-53. The evolution of Ga NMR parameters with CO2loading levels in Ga-MIL-53 reveals that the specific CO2loading level offers a profound degree of control over the MOF phase, and the data also suggests that a re-entrant phase transition is present. Adsorption of various organic compounds within Ga-MIL-53 has been investigated using a combination of thermal gravimetric analysis (TGA), powder X-ray diffraction (pXRD) and69/71Ga SSNMR experiments. Notably, pXRD experiments reveal that guest adsorption and host-guest interactions trigger unambiguous changes in the long-range structure of Ga-MIL-53, while69/71Ga SSNMR parameters yield valuable information regarding the effect of the organic adsorbates on the local GaO6environments. This approach shows promise for the ultra-wideline investigation of other quadrupolar metal nuclei in MIL-53 (e.g., In-MIL-53) and MOFs in general, particularly in regards to adsorption-related applications.
authors.affiliation: Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7.
authors.forename: Bryan E G
authors.initials: BEG
authors.lastname: Lucier
authors.affiliation: Department of Chemistry, University of Ottawa, Ottawa, Ontario, Canada K1N 6N5.
authors.forename: Victor V
authors.initials: VV
authors.lastname: Terskikh
authors.affiliation: Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7.
authors.forename: Renlong
authors.initials: R
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 5B7. Electronic address: yhuang@uwo.ca.
authors.forename: Yining
authors.initials: Y
authors.lastname: Huang