Sun Lei, Hendon Christopher H, Park Sarah S, Tulchinsky Yuri, Wan Ruomeng, Wang Fang, Walsh Aron, Dincă Mircea
Department of Chemistry , Massachusetts Institute of Technology , Cambridge , MA 02139 , USA . Email:
Department of Materials , Imperial College London , London SW7 2AZ , UK.
Chem Sci. 2017 Jun 1;8(6):4450-4457. doi: 10.1039/c7sc00647k. Epub 2017 Apr 20.
Identifying the metal ions that optimize charge transport and charge density in metal-organic frameworks is critical for systematic improvements in the electrical conductivity in these materials. In this work, we measure the electrical conductivity and activation energy for twenty different MOFs pertaining to four distinct structural families: M(DOBDC)(DMF) (M = Mg, Mn, Fe, Co, Ni, Cu, Zn); HDOBDC = 2,5-dihydroxybenzene-1,4-dicarboxylic acid; DMF = ,-dimethylformamide), M(DSBDC)(DMF) (M = Mn, Fe; HDSBDC = 2,5-disulfhydrylbenzene-1,4-dicarboxylic acid), MCl(BTDD)(DMF) (M = Mn, Fe, Co, Ni; HBTDD = bis(1-1,2,3-triazolo[4,5-b],[4',5'-]dibenzo[1,4]dioxin), and M(1,2,3-triazolate) (M = Mg, Mn, Fe, Co, Cu, Zn, Cd). This comprehensive study allows us to single-out iron as the metal ion that leads to the best electrical properties. The iron-based MOFs exhibit at least five orders of magnitude higher electrical conductivity and significantly smaller charge activation energies across all different MOF families studied here and stand out materials made from all other metal ions considered here. We attribute the unique electrical properties of iron-based MOFs to the high-energy valence electrons of Fe and the Fe mixed valency. These results reveal that incorporating Fe in the charge transport pathways of MOFs and introducing mixed valency are valuable strategies for improving electrical conductivity in this important class of porous materials.
确定能优化金属有机框架中电荷传输和电荷密度的金属离子，对于系统性提高这些材料的电导率至关重要。在这项工作中，我们测量了属于四个不同结构家族的二十种不同金属有机框架的电导率和活化能：M(DOBDC)(DMF)（M = 镁、锰、铁、钴、镍、铜、锌；HDOBDC = 2,5 - 二羟基苯 - 1,4 - 二羧酸；DMF = N,N - 二甲基甲酰胺）、M(DSBDC)(DMF)（M = 锰、铁；HDSBDC = 2,5 - 二巯基苯 - 1,4 - 二羧酸）、MCl(BTDD)(DMF)（M = 锰、铁、钴、镍；HBTDD = 双(1,2,3 - 三唑并[4,5 - b],[4',5'-]二苯并[1,4]二恶英）以及M(1,2,3 - 三唑酸盐)（M = 镁、锰、铁、钴、铜、锌、镉）。这项全面的研究使我们能够选出铁作为导致最佳电学性能的金属离子。在此研究的所有不同金属有机框架家族中，铁基金属有机框架的电导率至少高五个数量级，且电荷活化能显著更小，在所有考虑的其他金属离子制成的材料中脱颖而出。我们将铁基金属有机框架独特的电学性能归因于铁的高能价电子和铁的混合价态。这些结果表明，在金属有机框架的电荷传输途径中引入铁并引入混合价态，是提高这类重要多孔材料电导率的有价值策略。
