Photolytic C–O Bond Cleavage with Quantum Dots

Abstract

Quantum dots are used as photoredox catalysts to drive bond cleavage in lignin model substrates. Cadmium selenide quantum dots selectively cleave C–O bonds with yields comparable to the best transition-metal-based molecular photocatalysts, thereby emulating depolymerization of the β-O-4 linkages that account for 45–60% of all linkers in native lignin. Compared to their molecular catalyst counterparts, the quantum dots demonstrate higher turnover frequencies, higher surface tunability for solvent versatility, and lower catalyst loading under mild, ambient temperature reaction conditions. The robust nature and solvent versatility of these quantum dot photoredox catalysts enable a direct, single-vessel route to convert benzylic alcohols (a majority of species in native and processed lignin) into high-value guaiacols and acetophenones without any prerequisite filtration, purification, or solvent change.