Covalent/Metal-organic framework (COF/MOF) is a 2D/3D network compound of organic molecules (linkages) connected by linker molecules. This material possesses a set of flat bands (at least in a tight-binding level).  Typical examples of the linker network are Kagome/Pyrochlore lattices in 2D/3D. Based on the idea of the molecule orbital construction of the flat band systems, their flat band energies and wave-functions are explicitly obtained just by solving electronic states of an isolated linkage molecule. This method is applicable for series of (virtual) materials in any spatial dimension. It has been appeared in “Flat-band solutions in
D-dimensional decorated diamond and pyrochlore lattices: Reduction to molecular problem”,  by Tomonari Mizoguchi, Hosho Katsura, Isao Maruyama, and Yasuhiro Hatsugai, Phys. Rev. B 104, 035155 – Published 27 July 2021. See also arXiv:2103.14355.