Synthesizing and Investigating the Exotic Electronic Properties of Two-Dimensional Metal-Organic Frameworks

Project Information

EMOF

Grant agreement ID: 839242

DOI

10.3030/839242

Project closed

EC signature date 10 April 2019

Start date 1 September 2020

End date 31 August 2022

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 190 680,96

EU contribution

€ 190 680,96

Coordinated by

AALTO KORKEAKOULUSAATIO SR
Finland

Periodic Reporting for period 1 - EMOF (Synthesizing and Investigating the Exotic Electronic Properties of Two-Dimensional Metal-Organic Frameworks)

Reporting period: 2020-09-01 to 2022-08-31

Summary of the context and overall objectives of the project

The overall objective of this project is to synthesize novel organic materials and investigate their exotic electronic properties. Organic electronics are more environmentally friendly throughout the product lifecycle, from raw materials to disposal. Furthermore, organic materials have the added advantages of low cost, easy fabrication, and mechanical flexibility.
In this project, we have fabricated several novel organic materials under ultra-high vacuum (UHV) conditions and used low-temperature scanning tunneling microscopy (lt-STM) with non-contact atomic force microscopy (nc-AFM) to characterize their structural and electronic properties.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We have successfully synthesized an ultraflat biphenylene carbon sheet consisting of sp2-hybridized carbon atoms forming four-, six-, and eight-membered rings through an on-surface interpolymer dehydrofluorination (HF-zipping) reaction. Scanning tunneling spectroscopy revealed that this carbon allotrope is metallic. This work is published in Science (2021, 372, 852).
We managed to fabricate 2D monolayer Cu-dicyanoanthracene(DCA) metal-organic frameworks (MOF) with long-range order on an epitaxial graphene surface. The ordered DCA3Cu2 network shows a structure combining a honeycomb lattice of Cu atoms with a kagome lattice of DCA molecules and is predicted to be a 2D topological insulator. We confirm that a kagome band structure is formed in the 2D MOF near the Fermi level. In addition, we found that multiple molecular charge states can be generated and modified through the tip-induced local electric fields. This work is published in Advanced Functional Materials (2021, 31, 2100519).
We further extend the synthesis and electronic tunability of 2D MOFs beyond the electronically less relevant metal and semiconducting surfaces to superconducting substrates. Monolayer 2D Cu-DCA MOF has been well-grown on a 2D van der Waals NbSe2 superconducting substrate. This work allows us to follow the formation of the kagome band structure of the 2D MOF from the Star of David-shaped building blocks. This work is published in ACS Nano (2021, 15, 11, 17813).
These works attracted widespread attention within and even beyond the academic community. Relevant achievements have been reported by many academic media and cited in many important review articles and academic monographs.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

We expect the interpolymer HF-zipping strategy could be applied to synthesize other nonbenzenoid carbon allotropes. The combination of 2D materials into vertical heterostructures has emerged as a promising path to designer quantum materials with exotic properties. We extend this concept from inorganic 2D materials to 2D MOFs that offer additional flexibility in realizing designer heterostructures.
The research outputs have attracted broad attention in related fields. The exotic electronic properties of these organic materials encouraged cooperation between chemists and organic synthesis with physicists working on transport measurements. The findings of the project will have a long-term impact with potential applications of novel organic materials in dissipationless electronics, molecular electronics, and spintronics.

synthesis strategies, structural and electronic properties of biphenylene sheet

2D MOFs on epitaxial graphene and NbSe2 surface