Semiartificial CO₂ Fixation Using Metal-Dependent Formate Dehydrogenase

Semiartificial photosynthesis exploits synergies between synthetic light absorbers and biological catalysts, offering a promising strategy for solar chemistry. Unlike conventional synthetic catalysts for carbon dioxide (CO₂) fixation, biological systems employ enzymes, most notably formate dehydrogenases (Fdhs), to catalyze the interconversion between CO₂, protons and electrons into formate, a central hub molecule in energy and carbon metabolism. This review focuses on the deployment of metal-dependent Fdhs in semiartificial photosynthesis, with an emphasis on molybdenum- and tungsten-dependent enzymes directly wired to electrodes and synthetic light absorbers. We first examine the structural, mechanistic, and redox properties of relevant Fdhs in vivo and in vitro, highlighting reaction pathways and inherent challenges. Subsequent sections discuss the central role of biotic-abiotic interfaces in constructing functional biohybrid systems, highlighting how advanced interfacial characterization techniques inform enzyme loading, charge carrier dynamics, and reaction intermediates. We then summarize progress and challenges in (photo)electrochemical and photochemical systems leveraging Fdhs unique properties as a model catalyst for CO₂-to-formate conversion. This review aims to clarify the current state of the semiartificial photosynthesis field employing metal-dependent Fdhs in vitro, and guide future research at the interface of enzymology, photo(electro)chemistry, and materials science.