Nanobiomineralization of Carbon Dioxide by Molecularly Engineered Metal-Histidine Complex Nanozymes

Next-generation carbon capture, utilization, and storage (CCUS) technologies will be indispensable elements of global decarbonization efforts. In this context, permanent and rapid sequestration of carbon dioxide (CO₂) at high capacities will impact their utility broadly. CO₂ mineralization into solid inorganic carbonates is an appealing CCUS approach, which requires fast CO₂ hydration for effective implementation. The carbonic anhydrases (CAs) have, thus, gained considerable attention as rate promoters for CO₂ hydration. Nevertheless, the poor stability and high cost of CAs limit their practical application prospects. Here, we demonstrate that the molecular size control of histidine-based bolaamphiphiles (HisBolas) is a viable strategy for forming robust nanoarchitectures with unusual CA-like catalytic activity. HisBola molecules self-assemble into nanoparticles (∼40 nm) that fuse into globules in water, and the metal coordination of these supramolecular nanoassemblies results in nanozymes. The developed bioinspired nanozymes boost the CO₂ hydration kinetics, thus efficiently catalyzing the mineralization process. Systematically studying the alkyl chain length of HisBolas (HisBola5, 7, and 10), we optimized the catalytic activity of the nanozymes. The nanozyme with the optimum structure, zinc-coordinated HisBola5, showed the highest esterase activity [k_cat/K_m of ∼33.44 M^-1·s^-1 and Michaelis constant (K_m) of ∼0.29 mM] and CO₂ hydration kinetics (k_cat.hyd/K_m.hyd of ∼30,300 M^-1·s^-1 and K_m.hyd of ∼14 mM) among all metal-coordinated HisBolas screened. Overall, low-molecular-weight HisBolas offer a promising platform for designing metal-coordinated nanozymes with high catalytic activity, outstanding thermal stability, and rapid catalytic CO₂ hydration ability for CO₂ mineralization. We argue that the alkyl unit-controlled performance manipulation of produced nanozymes offers a new path for engineering supramolecular CA mimics, which share a common trait with proteinaceous enzymes, that is, the supporting role of noncatalytic units in catalytic activity.