Magnetic semiconducting 2D MOF

Metal-organic frameworks (MOFs) so far have been highlighted for their potential roles in catalysis, gas storage and separation. However, the realization of high electrical conductivity (>10-3 S/cm) and magnetic ordering in MOFs will afford them new functions for spintronics, which remains relatively unexplored. 

The groups from cfaed/TUD/HZDR/MPICPS/IKTS/XJTU demonstrate the synthesis of a two-dimensional MOF (2D MOF) by solvothermal methods using perthiolated coronene, namely 1,2,3,4,5,6,7,8,9,10,11,12-perthiolated coronene (PTC, reported by the same group (J. Am. Chem. Soc., 2017, 139, 2168-2171)), as a ligand and planar iron-bis(dithiolene) as linkages enabling a full p-d conjugation. Thus, such 2D MOF is featured with hexagonal lattices and van der Waals layer-stacking structure. Van der Pauw electrical measurement reveals the room temperature conductivity value of ~10 S/cm for bulk compressed pallet. A variable-temperature conductivity measurement displays a non-linear increase of conductivity with temperature, indicating a typical semiconducting behavior. A density functional theory (DFT) calculation is carried out to estimate the band gap as ~0.2 eV for a monolayer MOF. A variable-temperature magnetic susceptibility measurement as well as 57Fe Mössbauer spectra demonstrated that the PTC-Fe exhibit ferromagnetic ordering within nanoscale magnetic clusters at low temperatures (below ~20 K), thus evidencing exchange interactions between the intermediate spin iron(III) centers via the delocalized p electrons. Our work highlights conjugated 2D MOFs as a class of conductive materials exhibiting ferromagnetic and semiconducting features for potential spintronics application.

This work was financially supported by the ERC Grant on 2DMATER, EU Graphene Flagship, SPP 1928 (COORNET) and the German Science Council. We acknowledge the cfaed (Center for Advancing Electronics Dresden). We also thank Beamline BL14W1 at the Shanghai Synchrotron Radiation Facility (SSRF) for providing the beamtimes to carry out the XAS measurements. We acknowledge Dresden Center for Nanoanalysis (DCN) at TUD and Dr. Petr Formanek (Leibniz Institute for Polymer Research, IPF, Dresden) for the use of facilities, and we like to appreciate Prof. Stuart Parkin, Dr. Binghai Yan, Dr. Reinhard Berger and Mr. Chi Xu for the helpful discussion.

Reference:
Renhao Dong, Zhitao Zhang, Diana C. Tranca, Shengqiang Zhou, Mingchao Wang, Peter Adler, Zhongquan Liao, Feng Liu, Yan Sun, Wujun Shi, Zhe Zhang, Ehrenfried Zschech, Stefan C.B. Mannsfeld, Claudia Felser & Xinliang Feng*, A coronene-based semiconducting two-dimensional metal-organic framework with ferromagnetic behavior. Nat. Commun. 2018, DOI: 10.1038/s41467-018-05141-4.

Nature Communications