Computational Design of 3D Lantern Organic Framework

This study employed a computational approach, particularly Density Functional Theory at B3LYP-D3/6-31+G(d) level to design two new classes of three-dimensional (3D) Lantern Organic Frameworks (LOFs) materials based on trisilasumanene and porphyrin core building units. Particularly, we detail strategies for transitioning from 1D-LOF nanowires to extended 3D structures: first by connecting planar-molecule base units of trisilasumanene or porphyrin using benzene-based linkers, and then connecting silicon anchoring atoms on the bases with other bases that are vertically stacked by sp³-hydrocarbon chains. The 3D-LOF structures are designed to have different pore sizes through the use of various bases, bridges, and linkers. Comparisons of electronic properties of these 3D structures lead to one designing rule. That is, the gap between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the 3D materials depends only on its base and is nearly independent of the stack size or the length of the sp³-hydrocarbon bridges. Additionally, connecting base units with linkers also extends π-electron conjugation system leading to a reduction in HOMO-LUMO gap. For instance, linking two trisilasumanene molecules significantly narrows HOMO-LUMO gap by 1.75 eV while stacking these bases vertically and connecting them by linear pentane-based bridges yield insignificant change to the gap.