Interfacial engineering of ZIF-8/MXene membranes with hydrophilic–hydrophobic channels: CO2 nanobubble-mediated microalgal carbon fixation

Microalgal carbon sequestration offers a promising pathway for CO 2 mitigation, yet its efficiency is largely constrained by inherently low gas-liquid mass transfer. Herein, we report an interfacial engineering strategy to construct a ZIF-8/MXene composite membrane via pressure-assisted filtration. The membrane features unique hydrophilic–hydrophobic channels, wherein hydrophilic MXene nanosheets and hydrophobic ZIF-8 nanosheets act synergistically to effectively decouple bubble refinement from mass transfer resistance. This structural design enables the stable generation of monodisperse CO 2 nanobubbles with a mode diameter of 118.2 nm and the concentration of 1.62 × 10 9 particles mL −1 . The potential electrostatic adsorption facilitated by natural divalent cations in the BG-11 medium significantly shortens the mass transfer distance. Consequently, this promotes the formation of a localized CO 2 pseudo supersaturated microenvironment around the microalgae. This localized CO 2 enrichment potentially downregulates the carbon-concentrating mechanism, suggesting a strategic reallocation of cellular energy toward accelerated biomass accumulation. Consequently, the integrated system achieves an unprecedented biomass productivity of 0.76 g L −1 , offering an innovative material-biological paradigm for light-driven carbon capture and utilization.