Active site imprinting on Ti oxocluster metal–organic frameworks for photocatalytic hydrogen release from formic acid

Abstract

On-board hydrogen release from liquid organic carriers is a process that can make feasible the use of H₂ as a transportation fuel. Formic acid is considered as one of the most convenient liquid hydrogen organic carriers, and since it can be easily obtained from CO₂, it is water soluble which makes it unnecessary to recover the H₂-depleted byproducts. Compared to the more conventional thermal catalytic decomposition of formic acid, the use of light in combination with a photocatalyst has been much less explored. Herein, we report a new paradigm in MOF photocatalysis with the use of a microporous titanium oxocluster based metal–organic framework (Ti-MOF) endowed with formate-imprinted active sites, namely MIP-177-LT (MIP stands for Materials from Institute of Porous Materials of Paris, LT for Low Temperature), as a highly efficient photocatalyst for H₂ release from formic acid without the need to neutralize acidity or use sacrificial agents or noble metals. Noteworthily, a quantum efficiency of 22% has been determined for the photocatalytic H₂ release that is highly remarkable for a non-toxic noble metal-free photocatalyst.