The catalyst materials 0N-Cu-MOF, 1N-Cu-MOF, and 2N-Cu-MOF were successfully synthesized usinga solvothermal method, and using different concentrations of nitrogen-modified Cu organic frameworks (xN-Cu-MOF). Characterizations using X-ray diffraction (XRD), scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) surface area analysis showed that 1N-Cu-MOF had the largest SSA and pore size among the three materials synthesized. 1N-Cu-MOF exhibited the largest pore size and specific surface area among the three materials, which had a decisive effect on CO2 reduction. In addition, stability and CO2 reduction reaction (CO2RR) activity were evaluated by linear sweep voltmeter, cyclic voltmeter, electrochemical impedance spectroscopy, and time flow tests. Faradaic efficiency (FE) was determined by product analysis. Among the three catalyst materials, 1N-Cu-MOF showed the best catalytic performance at 50 mA･cm-2 (maximum current density). The charge transfer resistance was 8.23 Ω, the average current density was 19.9 mA･cm-2, and the FE of methane (CH4) production showed a high efficiency of 70.45 % when tested for 12 h at an overpotential of -0.35 V (to-RHE).

Abstract
1. Introduction
2. Experimental Procedure
    2.1. Chemicals
    2.2. Synthesis of 0N-Cu-MOF
    2.3. Synthesis of 1N-Cu-MOF
    2.4. Synthesis of 2N-Cu-MOF
    2.5. Characterization techniques
    2.6. Development of the working electrode
3. Results and Discussion
    3.1. Characterization
    3.2. Electrochemical Efficiency
4. Conclusion
References
Author Information

• Haixia Wang(Applied Technology College of Soochow University, Suzhou 215009, China)
• Yilei Sun(School of Chemistry and Life Sciences, Suzhou University of Science and Technology, Suzhou 215009, China)
• Yao Liu(School of Chemistry and Life Sciences, Suzhou University of Science and Technology, Suzhou 215009, China)
• Zeda Meng(School of Chemistry and Life Sciences, Suzhou University of Science and Technology, Suzhou 215009, China) Corresponding author
• Kunjie Li(Dong yang guang UACJ Fine Aluminum Foil Co., Ltd., Ruyuan, Guangdong, 512700, China)
• Won-Chun Oh(Department of Advanced Materials Science and Engineering, Hanseo University, Seosan 31962, Republic of Korea) Corresponding author