Design and Synthesis of a Single-Layer Ferromagnetic Metal–Organic Framework with Topological Nontrivial Gaps

Abstract

We report on the design and synthesis of a twodimensional metal−organic framework Fe 3 (HITP) 2 which comprises of a Kagome sublattice of Fe atoms. Density-functional theory calculations reveal that this framework has a ferromagnetic ground state with several topological nontrivial gaps opened due to the spin−orbit coupling, signifying quantum anomalous Hall features. Experimentally, we synthesize this structure by means of on-surface coordination self-assembly on an Au(111) substrate. We resolve its structure at a single-molecule resolution using scanning tunneling microscopy and confirm that the on-surface structure is nearly identical to the free-standing framework. We use scanning tunneling spectroscopy to study its electronic properties. A zero-bias resonance localized at the Fe atoms indicates that a magnetic moment is present at the Kagome lattice. Our results demonstrate the viability of realizing 2D organic quantum anomalous Hall systems.

Searching for kagome multi-bands and edge states in a predicted organic topological insulator

“…We discard its origin as a discrete molecular orbital 43,44 since no trace of such state exists at this energy when the molecules are uncoordinated with the Cu metal centers. 38,45 Instead, this broad state is the expected kagome multi-band of a 2D-MOF, [8][9][10][11][12][13][14][15][16][17][18] which (to the best of our knowledge) is experimentally reported here for the first time. Even though this MHK lattice is not covalently bonded, the conjugated band manifold is of comparable quality to the one recently reported for a 2D-COF.…”

“…[8][9][10][11][12] These are well-ordered, free standing 2D metal-organic frameworks (2D-MOFs), displaying a combination of kagome and honeycomb structures, where the metal centers provide the necessary SOC to the system to generate the topologically nontrivial edge states. Many examples can be found in the literature of such mixed honeycomb-kagome (MHK) lattices which are prone to exhibit interesting electronic properties, [13][14][15][16][17][18] however, their electronic conjugation is still debatable.…”

Two-Dimensional Metal–Organic Framework on Superconducting NbSe2

“…2D MOFs have been synthesized on metal surfaces by following the concepts of supramolecular coordination chemistry. , So far, most of the 2D MOFs are made on coinage metal surfaces, − where the interaction with the metal substrate strongly masks the intrinsic electronic properties of the MOF. This can be overcome by using weakly interacting substrates (such as graphene and hBN) that allow probing of the intrinsic exotic electronic properties of 2D MOFs. − However, to realize the exciting prospect of truly designer materials, it is important to demonstrate MOF synthesis on other 2D substrates.…”

Correlation-induced magnetism in substrate-supported 2D metal-organic frameworks

“…Substrates support, template, and enable the bottom-up synthesis of 2D MOFs [10][11][12] . These substrates can facilitate new functionalities via effects such as charge doping 24,25 , hybridisation [26][27][28] , strain 29 , symmetry breaking 30 , rearrangement of bonds facilitating magnetism 31 , and the Kondo effect [32][33][34][35][36][37] . Substrates are sometimes deleterious, such as through excessive hybridisation or unfavourable symmetry breaking 30 , and sometimes beneficial, such as through mediating magnetic interactions 34,38 or favourable charge transfer 39 .…”