Catalytic activity of Microcystis aeruginosa in Fe-Co-MOFs system for efficient CO2 fixation and high-value conversion

The enrichment efficiency during the high-value conversion of carbon dioxide still presents certain limitations in practical applications. Iron-cobalt-based metal-organic framework (MOF) nanoparticles, which exhibit lower toxicity to Microcystis aeruginosa , have been successfully introduced into microalgae solutions to address the issue of low CO 2 concentration in interfacial reactions. When 1,4-naphthalenedicarboxylic acid was employed as an organic ligand under synthesis conditions of 130°C, pH 3.5, and a reaction time of 15 h, the resulting MOF exhibited a CH₄ yield of 92.6 μmol g⁻¹ h⁻¹ in the photocatalytic system at room temperature (25°C). The combination of Microcystis aeruginosa with the optimal Fe-Co-MOFs system achieved a selectivity of up to 96.1 % in converting CO 2 into CH 4 . When Microcystis aeruginosa was cultured in a modified medium with a pH of 6.78 and 5 mg of NDC-T130 at 25°C for 12 h, an OD 600 of 0.192 ± 0.01 was observed. The CH₄ yield from the Microcystis aeruginosa -NDC-T130 co-culture composite system was 1.46 times that of the Fe-Co-MOFs. Density-functional theory calculations indicate that carbon dioxide molecules preferentially adsorb on the crystal surfaces of (CoFe 2 )O 4 (113) and (Co 0.457 Fe 0.543 )(Co 1.543 Fe 0.457 )O 4 (311), with the Co site being more likely to serve as the reactive site for CO 2 photoreduction to CH 4 within the Fe-Co-MOFs. Transcriptome analysis demonstrates that MOFs enhance the dark reactions of microalgae and facilitate further CO 2 fixation for photosynthesis and electron transfer, which are crucial for improving the high-value CO 2 conversion efficiency of this system. This strategy provides both experimental and theoretical support for iron-based MOFs as photocatalytic materials, regardless of CO 2 concentration.