Self-Supported ZIF-Based nanozymes with high catalytic activity and enhanced stability for CO2 capture

In the field of CO₂ capture from industrial flue gases via organic amine absorption process, utilizing metal–organic frameworks (MOFs) as biomimetic enzymes to mimic the catalytic activity of natural carbonic anhydrase (CA) for CO₂ hydration reaction represents a promising strategy. However, overcoming their inherent limitations, such as low catalytic activity and recyclability issues arising from their nanoscale dimensions, is essential for practical application. This study proposes key enhancements to zeolitic imidazolate frameworks (ZIFs) reported in the literature to improve CO₂ processing efficiency. Drawing inspiration from natural enzyme immobilization strategies, a series of self-supported ZIF-based nanozymes were synthesized using various methods, including catalytic site modulation, carrier immobilization, surfactant regulation and metal ion doping. These approaches enabled the fabrication diverse self-supported ZIF-based nanozymes with tunable structures. Starting with TiO₂, a range of self-supported biomimetic CA were synthesized with a carrier size of approximately 2 μm by substituting ZIF-8 and ZIF-67 carriers and introducing metal doping, aiming to leverage nanomaterial size effects to maximize catalytic performance while ensuring recyclability. The pristine ZIF-8 exhibited an esterase activity of 0.10 U·mg⁻¹, whereas the optimal self-supported ZIF-based nanozyme reached 0.23 U·mg⁻¹ at 25 °C and 2.75 U·mg⁻¹ at 80 °C. Notably, the self-supported nanozyme mitigated agglomeration issues and demonstrated superior activity, stability and recyclability in representative absorption systems.