Bridging Capture Chemistry to Low-Energy Bio-Integrated CO2-to-Methane

Anthropogenic CO2 emissions from flue gases pose a gigaton-scale challenge, which incremental improvements to conventional CO2 capture technologies alone cannot address. Bio-integrated carbon capture and utilization (BICCU) rethinks classical absorption-based CO2 capture by directly coupling chemical CO2 capture with bio-mediated conversion, eliminating the energy-intensive thermal desorption of conventional CO2 capture. However, the success of coupling capture agents with archaeal biocatalysts is constrained by incompatibility, as most capture agents exhibit antimicrobial properties. Herein, a design framework was developed to integrate capture chemistry with CO2-based biotechnology by combining abiotic CO2 loading, biotic assays, and kinetic modeling to correlate these processes with the physicochemical properties of a broad library of agents. Octanol-water partitioning, topological polar surface area, and hydrophilic groups were identified as key parameters for tuning capture agents toward biocompatibility, as these molecular traits influence hydrophobicity and membrane permeability. Guided by these discoveries, new capture agents can be discovered, as demonstrated by the synthesis of (diethanolamine)3triazine with a standardized biocompatibility of 1078 mMCO2, which is a 6.4-fold increase compared to conventional agents such as melamine of merely 168 mMCO2. These principles establish a blueprint for designing next-generation agents, unlocking bio-mediated CO2 valorization for scalable, low-energy methane production from diluted CO2 sources.