  The combination of two-dimensional (2D) materials into vertical
heterostructures has emerged as a promising path to designer quantum materials
with exotic properties. Here, we extend this concept from inorganic 2D
materials to 2D metal-organic frameworks (MOFs) that offer additional
flexibility in realizing designer heterostructures. We successfully fabricate a
monolayer 2D Cu-dicyanoanthracene MOF on a 2D van der Waals NbSe$_2$
superconducting substrate. The structural and electronic properties of two
different phases of the 2D MOF are characterized by low-temperature scanning
tunneling microscopy (STM) and spectroscopy (STS), complemented by
density-functional theory (DFT) calculations. These experiments allow us to
follow the formation of the kagome bandstructure from Star of David -shaped
building blocks. This work extends the synthesis and electronic tuneability of
2D MOFs beyond the electronically less relevant metal and semiconducting
surfaces to superconducting substrates, which are needed for the development of
emerging quantum materials such as topological superconductors.
