Developing O2-selective adsorbents that can produce high-purity oxygen from air remains a significant challenge. Here, we show that chemically reduced metal-organic framework materials of the type AxFe2(bdp)3 (A = Na+, K+; bdp2- = 1,4-benzenedipyrazolate; 0 < x ≤ 2), which feature coordinatively saturated iron centers, are capable of strong and selective adsorption of O2 over N2 at ambient (25 °C) or even elevated (200 °C) temperature. A combination of gas adsorption analysis, single-crystal X-ray diffraction, magnetic susceptibility measurements, and a range of spectroscopic methods, including 23Na solid-state NMR, Mössbauer, and X-ray photoelectron spectroscopies, are employed as probes of O2 uptake. Significantly, the results support a selective adsorption mechanism involving outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations that reside in the one-dimensional triangular pores of the structure. We further demonstrate O2 uptake behavior similar to that of AxFe2(bdp)3 in an expanded-pore framework analogue and thereby gain additional insight into the O2 adsorption mechanism. The chemical reduction of a robust metal-organic framework to render it capable of binding O2 through such an outer-sphere electron transfer mechanism represents a promising and underexplored strategy for the design of next-generation O2 adsorbents.
Developing O2-selective adsorbents that can produce high-purity n class="Chemical">oxygen from air remains a significant challenge. Here, we show that chemically reduced metal-organic framework materials of the type AxFe2(bdp)3 (A = Na+, K+; bdp2- = 1,4-benzenedipyrazolate; 0 < x ≤ 2), which feature coordinatively saturated iron centers, are capable of strong and selective adsorption of O2 over N2 at ambient (25 °C) or even elevated (200 °C) temperature. A combination of gas adsorption analysis, single-crystal X-ray diffraction, magnetic susceptibility measurements, and a range of spectroscopic methods, including 23Na solid-state NMR, Mössbauer, and X-ray photoelectron spectroscopies, are employed as probes of O2 uptake. Significantly, the results support a selective adsorption mechanism involving outer-sphere electron transfer from the framework to form superoxide species, which are subsequently stabilized by intercalated alkali metal cations that reside in the one-dimensional triangular pores of the structure. We further demonstrate O2 uptake behavior similar to that of AxFe2(bdp)3 in an expanded-pore framework analogue and thereby gain additional insight into the O2 adsorption mechanism. The chemical reduction of a robust metal-organic framework to render it capable of binding O2 through such an outer-sphere electron transfer mechanism represents a promising and underexplored strategy for the design of next-generation O2 adsorbents.
Authors: Peter D Southon; David J Price; Pia K Nielsen; Christine J McKenzie; Cameron J Kepert Journal: J Am Chem Soc Date: 2011-06-28 Impact factor: 15.419
Authors: Eric D Bloch; Leslie J Murray; Wendy L Queen; Sachin Chavan; Sergey N Maximoff; Julian P Bigi; Rajamani Krishna; Vanessa K Peterson; Fernande Grandjean; Gary J Long; Berend Smit; Silvia Bordiga; Craig M Brown; Jeffrey R Long Journal: J Am Chem Soc Date: 2011-08-26 Impact factor: 15.419
Authors: Natalia M Padial; Elsa Quartapelle Procopio; Carmen Montoro; Elena López; J Enrique Oltra; Valentina Colombo; Angelo Maspero; Norberto Masciocchi; Simona Galli; Irena Senkovska; Stefan Kaskel; Elisa Barea; Jorge A R Navarro Journal: Angew Chem Int Ed Engl Date: 2013-06-26 Impact factor: 15.336
Authors: Kurtis M Carsch; Andrei Iliescu; Ryan D McGillicuddy; Jarad A Mason; Theodore A Betley Journal: J Am Chem Soc Date: 2021-10-21 Impact factor: 16.383