Laccase-engineered HOF-102 for pH-resilient photoelectrochemical biosensing

Immobilization on suitable supports has become an effective strategy to enhance enzymes' stability, reusability, and environmental adaptability under non-physiological or harsh conditions. In this work, we developed a one-pot self-assembly strategy to synthesize palladium nanoparticles (PdNPs)-decorated laccase (Lac) encapsulated within a hydrogen-bonded organic framework (HOF-102), denoted as Lac/PdNPs@HOF-102, through an in-situ photo-reduction and enzyme-triggered HOF-102 formation process. Specifically, the amino groups on the Lac surface initiated the rapid nucleation of H 4 TNAPy, followed by self-assembly to construct the HOF-102 framework. Simultaneously, Pd 2+ ions were photoreduced in situ to form PdNPs confined within the HOF-102 pores, yielding a multifunctional HOF composite with embedded Lac. The encapsulated Lac maintained stable catalytic performance within pH range of 2–7.4 and retained over 60% of its activity within pH range of 8–10, whereas free enzymes rapidly lost their activity under both conditions. It attributed to the highly ordered three-dimensional structure of HOF-102, which effectively immobilizes enzyme molecules and provides a protective microenvironment that shields the active center from external fluctuations. Using PdNPs@HOF-102 as the photoactive material and Lac as the recognition element, a photoelectrochemical (PEC) sensor was constructed for the detection of catechol. The resulting sensor exhibited a wide linear range (1 μM–900 μM) and a low detection limit (0.72 μM, S/N = 3). This work not only establishes a versatile HOF-based PEC biosensing platform but also demonstrates that the broadened pH tolerance of Lac/PdNPs@HOF-102 significantly expands the operational scope of enzyme-based systems, enabling their application in complex environments.