To deduce the reason for the regioselective, strong adsorption, we analyzed the electronic structures using multiple methods. We start discussing the HOMA values (Figure ) and Hirshfeld-I partial charges (Figure ). The HOMA value (Figure ) is a geometric indicator for aromaticity which has been used successfully for investigating the aromaticity change of the adsorbate upon surface adsorption in the past. Here, we extend the indicator to understand the aromaticity change in the substrate upon adsorption. From the 6-rings to the 8-rings and 4-rings, decreasing aromaticity is observed with HOMA values of 0.49 (6-rings ), 0.37 (8-rings) to -0.47 (4-rings), respectively (Figure ).