Constructing a photo-enzymatic cascade reaction and its in situ monitoring: enzymes hierarchically trapped in titania meso-porous MOFs as a new photosynthesis platform

Abstract

A photocatalysis-enzyme coupled system represents a most promising approach towards artificial photosynthesis and a direct use of solar energy for the synthesis of specific organic molecules or fuel. In contrast to extensively explored semiconductor photocatalysts, studies that successfully combine photocatalytic and enzymatic reactions are rare. In the present work we describe a photocatalyst–enzyme coupled approach that relies on the in situ synthesis of a hierarchically porous (hp) metal–organic framework (here using titania-based MIL-125) formed in the nanochannels of a TiO₂ membrane. By engineering the nm-scale pore size in the MOF we achieve trapping of active cytochrome C (CytC). Benefiting from the intrinsic photocatalytic activity of the MOF [MIL-125 (Ti)] we develop a functional photocatalyst–enzyme system that is active under visible light. Moreover, the membrane-based architecture allows for in situ triggering and monitoring of the enzymatic reaction. Therefore, the platform represents not only a nanoscale photocatalytic reactor or device but also allows to monitor and understand photocatalytically coupled enzyme reactions.