Rapid in situ encapsulation of [NiFe]-hydrogenase into covalent organic frameworks for robust hydrogen oxidation and evolution

Abstract

[NiFe] hydrogenases are highly efficient metalloenzymes capable of reversibly converting hydrogen gas into protons and electrons, positioning them as valuable catalysts for sustainable hydrogen production and bioenergy systems. However, their practical deployment is limited by poor stability and the difficulty of integrating them into solid supports without compromising activity. Covalent organic frameworks (COFs) offer a promising platform for enzyme immobilization due to their high surface area, adjustable pore environments, and robust chemical stability. These features can improve enzyme loading, protect structural integrity, and enhance overall catalytic performance. Here, we report a rapid in-situ encapsulation strategy that embeds [NiFe] hydrogenase directly into the network of a 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa) β-ketoenamine COF (denoted MBH@TpPa) within 10 minutes. This approach bypasses multistep post-synthetic procedures typically required for enzyme immobilization and preserves the intrinsic activity of the enzyme. The resulting MBH@TpPa biohybrid exhibits outstanding photocatalytic hydrogen evolution activity, achieving 2.59 mmol g^-1 h^-1, a 43-fold enhancement over the pristine COF and more than triple the performance of Pt-loaded TpPa. In addition, MBH@TpPa catalyzes hydrogen oxidation, a more demanding transformation, demonstrating its bidirectional reactivity. These results establish MBH@TpPa as a versatile and robust biohybrid catalyst with significant potential for solar-driven and renewable energy applications.