Electron delocalization and charge mobility as a function of reduction in a metal–organic framework

Aubrey, M. L.; Wiers, B. M.; Andrews, S. C.; Sakurai, T.; Reyes-Lillo, S. E.; Hamed, S. M.; Yu, C.-J.; Darago, L. E.; Mason, J. A.; Baeg, J.-O.; Grandjean, F.; Long, G. J.; Seki, S.; Neaton J. B.; Yang P.; Long, J. R. Nature Materials 2018, 17, 625.


Conductive metal–organic frameworks are an emerging class of three-dimensional architectures with degrees of modularity, synthetic flexibility and structural predictability that are unprecedented in other porous materials. However, engendering long-range charge delocalization and establishing synthetic strategies that are broadly applicable to the diverse range of structures encountered for this class of materials remain challenging. Here, we report the synthesis of KxFe2(BDP)3 (0 ≤ x ≤ 2; BDP2− = 1,4-benzenedipyrazolate), which exhibits full charge delocalization within the parent framework and charge mobilities comparable to technologically relevant polymers and ceramics. Through a battery of spectroscopic methods, computational techniques and single-microcrystal field-effect transistor measurements, we demonstrate that fractional reduction of Fe2(BDP)3 results in a metal–organic framework that displays a nearly 10,000-fold enhancement in conductivity along a single crystallographic axis. The attainment of such properties in a KxFe2(BDP)3 field-effect transistor represents the realization of a general synthetic strategy for the creation of new porous conductor-based devices.

  1. Biggins, N.; Ziebel, M. E.; Gonzalez, M.; Long, J. R. Crystallographic Characterization of the Metal-Organic Framework Fe2(BDP)3 upon Reductive Cation Insertion Chem. Sci. 2020, 11, 8196.
  2. Jaffe, A.; Ziebel, M. E.; Halat, D. M.; Biggins, N.; Murphy, R. A.; Chakarawet, K.; Reimer, J. A.; Long, J. R. Selective, High-Temperature O2 Adsorption in Chemically Reduced, Redox-Active Iron-Pyrazolate Metal–Organic Frameworks J. Am. Chem. Soc. 2020, 142, 14627–14637.
  3. Xie, L. S.; Sun, L.; Wan, R.; Park, S. S.; DeGayner, J.; Hendon, C. H.; Dincă, M. Tunable Mixed-Valence Doping towards Record Electrical Conductivity in a Three-Dimensional Metal–Organic Framework J. Am. Chem. Soc. 2018, 140, 7411-7414.
  4. Herm, Z. R.; Wiers, B. M.; Mason, J. A.; van Baten, J. M.; Hudson, M. R.; Zajdel, P.; Brown, C. M.; Masciocchi, N.; Krishna, R.; Long, J. R. Separation of Hexane Isomers in a Metal-Organic Framework with Triangular Channels Science Science 2013, 340, 960–964.