We estimate that the smallest SWCNTs in our experiments have a diameter of ~2 nm. To model the SWCNT, we use a large C116H28 graphitic sheet with curvature matching that of a SWCNT with 2 nm diameter (Supplementary Fig. and); the 116 C atoms provide ample surface area for coordinating CoPc. We then placed a flat CoPc catalyst within van der Waals distance of the outside of the SWCNT. With the H atoms of the SWCNT frozen, we optimized the geometry of the CoPc when near the outside of the SWCNT wall. The MD simulation shows that the CoPc curves around the C116H28 such that the curvature of the catalyst and the CNT are equal. Additionally, the curved plane of the catalyst lies ~3.11 Å from the wall of the SWCNT, indicating significant p-p stacking between the catalyst and the SWCNT. We also explored how CoPc interacts with a large, flat sheet of carbon, which represents the MWCNT. In this case, the CoPc plane remained parallel to the flat C116H28 sheet with the distance between the two planes being ~3.37 Å. The predicted structures agree well with our XANES and EXAFS analyses.