Conjugated Microporous Polymers Bearing Poly(Acrylic Acid) Brushes: Site-Specific Rhodium Immobilization for Efficient and Enzyme-Compatible Photocatalytic NADH Regeneration.

Photocatalytic NADH regeneration is limited by poor recovery of the rhodium mediator (Rh*) and enzyme deactivation caused by free Rh* species and photogenerated holes. In this study, we introduce poly(acrylic acid) brushes grafted onto conjugated microporous polymers (CMPs) to anchor Rh* complexes (cPTT-P-Rh*). The negatively charged brushes ensure excellent dispersibility and prevent Rh* leaching via electrostatic interactions. They also serve as a conductive pathway for internal electron transfer from the photocatalyst to the anchored Rh*, which is more efficient than intermolecular transfer. Moreover, the brushes physically shield photogenerated holes, protecting the enzyme from both free Rh* and hole-induced damage. Using a low-power 10 W 460 nm LED light, this system achieves 87.7% NADH regeneration (with exclusive 1,4-NADH production) within 15 min with a turnover frequency (TOF) of 93.3 h-1, comparable to the highest reported values in the literature. Notably, the enzyme retains 76.8% activity after photocatalysis, and circular dichroism confirms no damage to protein secondary structure. The catalyst maintains 61.1% activity after seven cycles. This brush design uniquely integrates immobilization, electron transfer, and protection for efficient photobiocatalysis.