The capture and conversion of CO₂ into valuable chemicals such as methanol (CH₃OH)
represents a promising strategy for mitigating industrial carbon emissions, particularly in hard�to-decarbonise sectors. The most well-developed systems for CO2 upgrading to CH3OH, while effective, face challenges relating to cost and sustainability. Enzyme-based catalysis, with the addition of carbonic anhydrase (CA) to enhance CO2 sequestration, offers a greener alternative due to its ability to enhance CO₂ hydration rates. For industrial application, enzyme recovery and reusability are crucial, and immobilisation is a common solution for this issue.
Porous frameworks are particularly popular, since they offer higher surface area (SA) for
enzyme loading. This study investigates two potential porous frameworks, biochar and
bioinspired silica (BIS), for their suitability in CA immobilisation.
A meta-analysis of biochar synthesis parameters (pyrolysis temperature, feedstock, and
activation treatment) revealed significant variability in porosity characteristics. No biochar
candidates met the minimum requirements for pore diameter (PD), pore volume (PV), and SA necessary for effective enzyme immobilisation and activity.
Subsequently, a recently developed BIS synthesis method was used to [redacted] frameworks, engineered to meet ideal porosity conditions. Porosity analyses confirmed that [redacted] samples exhibited suitable PV (>0.3 cm³ g-1) and SA (50 – 500 m² g-1), with [redacted] showing enhanced SA at higher reactant concentrations. CA was immobilised via entrapment and adsorption methods. While adsorption resulted in limited enzyme loading and activity, some [redacted] entrapped CA samples exhibited comparable activity to the free enzyme, indicating some potential as an industrial application but further rigorous development would be required.
Overall, this study highlights BIS as a promising, tunable platform for enzyme immobilisation, although further optimisation is needed to improve consistency and performance for industrial CO₂ capture and conversion applications.
