Interface-engineered iron single-atom biohybrids for efficient CO₂-to-bioplastic conversion

A hybrid system combining water electrolysis and H₂ autotrophic microorganism enables sustainable CO₂ valorization, but is hindered by low H₂ bioavailability and sluggish hydrogenase kinetics. Here, we report an interface-engineered inorganic-biological biohybrid, constructed by covalently anchoring iron single-atom catalysts (ISA) onto Cupriavidus necator (C.N@ISA) via click chemistry. The ISA anchored interface generates a localized H₂-rich microenvironment, accelerates H₂ dissociation, while the synergy between ISA and polyethylene glycol-phenylboronate linker stabilizes the inorganic-biological hybrid interface and promotes electron/proton transfer across microbial membrane. These coupled effects boost reduced form of nicotinamide adenine dinucleotide (NADH) regeneration and adenosine triphosphate (ATP) synthesis. In addition, ISA exhibits nanozyme-like activity, scavenging reactive oxygen species to protect cell viability. As a result, C.N@ISA achieves CO₂-to-bioplastic poly-β-hydroxybutyrate production of 1058.8 mg L^-1 with a Faradaic efficiency of 42.0%. Integrating theoretical calculations, electrochemical analysis, and transcriptomics confirms that ISA simultaneously enriches and activates H₂ while reinforcing intracellular metabolism, offering a generalizable strategy for carbon-negative biomanufacturing.