## 3 Results and Discussion
The results of XPS and XAF show that the strong interaction between these 3d metal ions in the heterojunction can synergistically  
Figure 3: (**a**) Total XPS spectra of Ni-MOF, ZIF-L and Ni-MOF@ZIF-L. (**b**) N 1s XPS spectra of ZIF-L and Ni-MOF@ZIF-L. (**c**) O 1s XPS spectra of Ni-MOF and Ni-MOF@ZIF-L. (**d**) Bond energies of Ni-MOF, ZIF-L, and Ni-MOF@ZIF-L. (**e**) Ni 2p XPS of Ni-MOF and heterojunction. (**f**) Co 2p XPS of ZIF-L and heterojunction. regulate the electronic structure, which is crucial for the high electronic conductivity and activity in the electrocatalytic CO\({}_{2}\)RR. Furthermore, periodic DFT calculations are also carried out to understand the interfacial electronic properties and chemical interactions of the Ni-MOF@ZIF-L heterojunction. Figure 5a shows the optimized heterojunction model structure. At the interface, the imidazole groups of ZIF-L directly interact with the exposed Ni and O atoms of the Ni-MOF surface. The calculated interfacial NH\(\cdots\)Ni and NH\(\cdots\)O distances are 12.2 A and 6.9 A at the PBE level, respectively, indicating no chemical bond formation between ZIF-L and Ni-MOF surfaces. Nevertheless, these two surfaces exhibit strong interaction, with an adsorption energy of 18.4 eV at the PBE level. Electronic structure analysis reveals significant electron transfer at the interface upon heterojunction formation compared to isolated ZIF-L and Ni-MOF surfaces. Charge difference analysis clearly shows approximately 1.9 \(\mid\)e\(\mid\) transferred from ZIF-L to Ni-MOF at the interface (evident from blue to yellow regions in Figure 5b). The charge reduction region is mainly located on the imidazole groups of the ZIF-L surface, while the charge accumulation is located on the Ni atoms of the Ni-MOF surface. Figure 5c further shows the plane-averaged charge density difference along the z direction, which is normal to the heterostructure. It is clear that the charge accumulation sharply takes place at the first layer of the Ni-MOF surface, though there is some small contribution at the second layer. In contrast, charge reduction occurs across a broader z-direction region. Further decomposition of the charge difference into the specific atoms reveals more interesting results, as shown in Figure 5d. The charge reduction mainly arises from the C, H, and O atoms of ZIF-L's imidazole groups, with Co atoms also contributing slightly. However, the charge accumulation preferentially localizes on the Ni atoms in the first layer of the Ni-MOF surface. These theoretical results are consistent with the XPS and EXAFS experimental data discussed previously. Moreover, we investigated the adsorption energies of CO\({}_{2}\) and H\({}_{2}\)O molecules on this optimized structure to reveal its competitive adsorption capability. The heterojunction shows a markedly enhanced CO\({}_{2}\) adsorption energy of 4.22 eV, significantly higher than the 0.34 eV of pure Ni-MOF. Notably, CO\({}_{2}\) molecules preferentially adsorb on the ZIF-L side, in agreement with N\({}_{2}\) adsorption results, which effectively increases CO\({}_{2}\) concentration around the Co-active sites and promotes CO\({}_{2}\) activation. Although the H\({}_{2}\)O adsorption energy on the heterojunction surface also increases substantially (from 1.86 eV to 5.99 eV), hydrogen bonding between H\({}_{2}\)O and the Ni-MOF surface causes H\({}_{2}\)O to accumulate predominantly on the Ni-MOF side. These results demonstrate that the heterojunction possesses both strong electron transfer capability and optimized chemical interactions with CO\({}_{2}\) and H\({}_{2}\)O molecules. Figure 4: (**a**) Ni/Co K-edge XANES spectra of Ni-MOF/ZIF-L and heterojunction. (**b**) Ni/Co K-edge EXAFS spectra of Ni-MOF/ZIF-L and heterojunction. The catalytic performance of the synthesized catalysts was evaluated in a neutral electrolyte using an H-type cell. As shown in Figure 6a, the apparent cathodic currents of these catalysts remain very small in the potential range of 0 to \(-\)0.5 V, suggesting negligible CO\({}_{2}\)RR activity.