Enhancing CO dissolution and inorganic carbon conversion by metal-organic frameworks improves microalgal growth and carbon fixation efficiency.

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 CO solubility. The maximum specific surface area of MOFs reached 342.94 m·g at a Zn/Fe molar ratio of 10/1. Under the optimal MOFs concentrations of 2.5 mg·L, the conversion of inorganic carbon increased by 2.6-fold. When S. obliquuswas cultured in a MOFs-modified medium with 1.50 % CO at 25 °C, the CO mass transfer coefficient and mixing time reached 9.01 × 10 min and 55 s, respectively. The maximum chlorophyll-a content, biomass productivity, and CO fixation efficiency reached 32.57 mg·L, 0.240 g·L·d and 21.6 %, respectively. Enriching CO 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 CO fixation efficiency.