Metagenomic insights into the improvement of CO2/H2 biomethanation or biogas upgrading using zirconium metal organic frameworks

The inefficient conversion of carbon dioxide (CO 2 ) to methane often restricts the advancement of CO 2 biomethanation technologies . This study explored the degrading performance, microbial community compositions, and functional gene abundance to examine the impact of zirconium metal-organic frameworks (Zr-MOFs) on the CO 2 biomethanation process. The results showed that the maximum utilization rates of CO 2 and H 2 increased by 2.77 times and 2.36 times after the addition of Zr-MOFs, respectively, and the corresponding conversion rate of CO 2 to methane also increased by 57.53%. Additionally, Zr-MOFs enhanced the COD removal efficiency and hydrolysis of tryptophan-like proteins and humic acid-like substances, resulting in more volatile organic compounds, such as tetradecane, 2-pentanone, and hexadecanoic acid. The analysis of microbial community structure revealed that the relative abundance of Methanothrix and Metanobacterium increased by 24.40% and 36.02% after the addition of Zr-MOFs, respectively. The methane metabolism revealed that Metanobacterium was a member of the same aceticlastic methanogenic pathway as Metanothrix , which encodes acetyl-CoA synthetase to catalyze the synthesis of acetyl-CoA from acetate, and Zr-MOFs also increased the relative abundance of genes that encode the enzyme responsible for converting intermediates to methane. Finally, Zr-MOFs improved the biogenesis and utilization of acetate and hydrogen (H 2 ) by enhancing the activity of enzymes, thereby providing more nutrients for methanogenesis . This study provided thorough explanations for the application and improvement of Zr-MOFs in CO 2 biomethanation technology.