Micellar-Colloidal Iron Oxyhydroxide-Integrated Hybrid-Composites Photocatalysts for Orthogonal Rhodium/Cobalt-Mediated NAD⁺/NADH Cycling and Mediator-Free Boronic Acid Hydroxylation

Abstract

The development of visible-light-driven photocatalysts that enable sustainable cofactor regeneration and concurrent organic transformations remains a significant challenge. We report iron oxyhydroxide-integrated composite frameworks; Btc/M and Btc/M-FeOOH, synthesized via a micelle-assisted strategy. Structural analyses confirmed moderate crystallinity, interparticle porosity, and effective incorporation of FeOOH (goethite), thereby enhancing π-conjugation and charge transfer. Under visible-light irradiation, both composite frameworks promoted orthogonal photo-regeneration of 1,4-NADH through a two-electron mediator cycle. Comparative studies using rhodium- and cobalt-based mediators (Rh-C and Co-C) revealed distinct regeneration efficiencies: Rhodium-based mediator (Rh-C) achieved efficiencies of 62.37% (TON = 2.06, TOF = 1.03 h⁻¹) for Btc/M and 95.49% (TON = 2.11, TOF = 1.05 h⁻¹) for Btc/M-FeOOH. The cobalt-based mediator (Co-C), a sustainable alternative, delivered 35.58% (TON = 1.37, TOF = 0.68 h⁻¹) and 78.18% (TON = 2.08, TOF = 1.04 h⁻¹), respectively. Beyond cofactor recycling, both composite frameworks enabled mediator-free hydroxylation of arylboronic acids to phenols with >97% conversion. This dual-function platform highlights composite-metal oxide organic-inorganic hybrid frameworks as efficient, sustainable photocatalysts for integrated biocatalytic and synthetic applications.