1. Upon M atom doping, for both M-BP1 and M-BP2 systems (Figs. 7 and S22), the electronic states at the E F of Sc, Ti, Co, Ni, and Zn atoms are predominantly from d orbitals, with Fe also showing minor s orbital contributions, indicating bonding mainly involves s and d orbitals of M dopants. Moreover, C N atom's electronic states at the E F are primarily from p orbitals after M doping, suggesting d(M)-p(C N ) interactions for Sc, Ti, Co, Ni, and Zn doped BP systems, while the ds(Fe)-p(C N ) interaction is more appropriate to describe the bonding between Fe and C N atoms. Upon CO adsorption, in the case of CO-Sc-BP1 (Fig. 8a), the overlap between the p orbitals of carbon in CO and the d orbitals of Sc atom within the -2.5 to 3 eV range signifies hybridization and an enhanced interaction with the Sc-BP1 matrix. This is consistent with the strong E ads results of 5.207 eV (Fig. 2b) and supports the notion that CO is strongly adsorbed onto the Sc-BP1 matrix. Similar hybridization patterns are observed in other CO-M-BP1 (Figs. 8b-8f) and CO-M-BP2 (Fig. S23) systems, implying robust interactions between the M-BP matrix and CO, thereby affirming the stabilities of the CO-M-BP systems;The same type of orbital hybridization is apparent in other M-BP1 (Figs. 7b-7f) and M-BP2 systems (Fig. S22)
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