Compartmentalized Encapsulation of Rhodium-Alginate Conjugate in Hybrid Hydrogen-Bonded Organic Frameworks for <i>In Situ</i> Cofactor Recycling and Biocatalysis

Sustainable enzymatic reactions with nicotinamide adenine dinucleotide (phosphate) (NAD(P))-dependent oxidoreductases need cofactor regeneration, and a pentamethylcyclopentadienyl rhodium (Rh) bipyridine complex has been recognized as a promising chemical catalyst for this purpose. However, efficient cofactor recycling using Rh catalysts faces challenges in preventing the mutual inactivation of Rh and enzymes and simultaneously enhancing the Rh catalyst stability. Herein, we find that sodium alginate (A) is compatible with Rh, thereby enabling the fabrication of a Rh-alginate conjugate (Rh-A) that protects the Rh activity. Moreover, Rh-A is encapsulated into a hydrogen-bonded organic framework (BioHOF-1), and Rh-A@BioHOF-1 exhibits outstanding stability. Then, the compartmentalized encapsulation of Rh-A@BioHOF-1 onto phenylacetone monooxygenase (PAMO) plus NADPH (N) in BioHOF-1 (Rh-A@HOF-on-PAMO&N@PAH-HOF) is achieved, where PAMO and N are coencapsulated in the interior with the assistance of poly(allylamine hydrochloride) (PAH). The composite nanoreactor allows for sustainable in situ cofactor regeneration and efficient biocatalysis, and it maintains excellent structural stability and reusability, retaining 72.7% of the biocatalytic activity in 10 cycles. The results collectively demonstrate the success of the Rh-alginate conjugation and hybrid HOF-based compartmentalization for integrating cofactor-regenerating chemoenzymatic systems in sustainable biomanufacturing.