Enhancing CO₂ dissolution and inorganic carbon conversion by metal-organic frameworks improves microalgal growth and...

Carbon supplementation strategies still have certain practical application constraints. Zn/Fe-based metal-organic frameworks (MOFs) nanoparticles that which are not toxic to Scenedesmus obliquus were successfully introduced into microalgal solutions to overcome low CO₂ solubility. The maximum specific surface area of MOFs reached 342.94 m²·g^-1 at a Zn/Fe molar ratio of 10/1. Under the optimal MOFs concentrations of 2.5 mg·L^-1, the conversion of inorganic carbon increased by 2.6-fold. When S. obliquuswas cultured in a MOFs-modified medium with 1.50 % CO₂ at 25 °C, the CO₂ mass transfer coefficient and mixing time reached 9.01 × 10^-3 min^-1 and 55 s, respectively. The maximum chlorophyll-a content, biomass productivity, and CO₂ fixation efficiency reached 32.57 mg·L^-1, 0.240 g·L^-1·d^-1 and 21.6 %, respectively. Enriching CO₂ for ribulose-1,5-bisphosphate carboxylase/oxygenase carboxylation by MOFs may be the key to improving the photosynthetic efficiency of microalgae. This strategy could serve as a reference for improving the microalgal CO₂ fixation efficiency.