(36b) Materials Exhibiting Biomimetic Carbon Fixation and Self-Repair: A Reaction Engineering Analysis of Carbon Fixing Materials

Recently, we introduced carbon fixing materials as a new class of self-healing, self-reinforcing materials for room temperature polymerization driven by atmospheric CO2. These materials consist of a photoabsorber and photocatalyst capable of converting atmospheric CO2 into an active, polymerizable monomer which is designed to automatically react with an existing, growing polymer backbone within the material, increasing its mass and mechanical properties, and repairing the matrix. This class of materials can utilize biological or non-biological photocatalysts and support a wide range of potential backbone chemistries. However, there is no analysis to date that describes their fundamental limits in terms of chemical kinetics and mass transfer.

In this work, we have developed a general analytical framework for the evaluation and benchmarking of any carbon fixing material. We employ a reaction engineering, and materials science analysis to answer basic questions about the maximum growth rate, photocatalytic requirements and limits of applicable materials. A Damköhler analysis is conducted to establish benchmarks for the photocatalytic reduction, polymerization rate, and CO₂ adsorption capacity beyond which the presented system is able to grow solid mass from atmospheric carbon dioxide. We have identified formaldehyde as a key C1 intermediate for polymerization, around which polymerization chemistries can be arranged to polymers. As a case study, we evaluated CO₂ reduction to formaldehyde and further polymerization to polyoxymethylene using the kinetic data reported in the literature for these reaction networks. This reaction engineering analysis introduces benchmarks for carbon fixing materials with respect to achievable rates of photocatalysis, mass transport, and polymerization. We determine ranges of catalytic activity and CO₂ adsorption capacity that will allow for maximum polyoxymethylene growth from atmospheric CO₂.