1：Experimental Design and Method Selection:

A facile two-step hydrothermal method was used to synthesize ZnNi MOF@ZnO nanowires array. ZnO nanowires were first synthesized hydrothermally, then coated with MOF-5 via immersion in a solution containing 1,4-benzenedicarboxylate, followed by ion exchange with Ni2+ ions to form ZnNi MOF.

2：Sample Selection and Data Sources:

Samples included bare ZnO nanowires array, MOF-5@ZnO, and ZnNi MOF@ZnO on FTO substrates. Data were obtained from characterization techniques and PEC measurements.

3：List of Experimental Equipment and Materials:

Equipment included SEM (JEOL-6700F), TEM (JEOL JEM-2010), XPS (VG ESCALAB 250), XRD (Philip X'Pert Pro MPP diffractometer), and electrochemical workstation (CHI 700E). Materials included zinc acetate dihydrate, KOH, zinc nitrate hexahydrate, hexamethylenetetramine, 1,4-benzenedicarboxylate, N,N-dimethylformamide, triethylamine, nickel nitrate, and sodium sulfate electrolyte.

4：Experimental Procedures and Operational Workflow:

ZnO nanowires were grown on FTO via hydrothermal synthesis. MOF-5 coating was achieved by immersing in a DMF/water/triethylamine solution with BDC at 60°C for 2h. Ion exchange was done by soaking in Ni(NO3)2 solution at 120°C for 3h. PEC measurements were conducted in a three-electrode cell with 0.5 M Na2SO4 electrolyte, using a 300 W Xenon lamp with AM 1.5 G filter as light source.

5：2h. Ion exchange was done by soaking in Ni(NO3)2 solution at 120°C for 3h. PEC measurements were conducted in a three-electrode cell with 5 M Na2SO4 electrolyte, using a 300 W Xenon lamp with AM 5 G filter as light source. Data Analysis Methods:

5. Data Analysis Methods: Data were analyzed using techniques such as SEM/TEM for morphology, XRD for structure, XPS for composition, and linear sweep voltammetry for PEC performance. Electrochemical impedance spectroscopy was used to study charge transfer.