Aluminum‐based Metal‐Organic Framework as Water‐tolerant Lewis Acid Catalyst for Selective Dihydroxyacetone Isomerization to Lactic Acid

Lactic acid is a renewable and versatile chemical for food, pharmaceuticals, cosmetics, and other chemicals. Lactic acid can be produced from biomass‐derived dihydroxyacetone. However, selective and recyclable water‐tolerant acid catalysts need to be developed for the specific production of lactic acid. Here we show that the MIL‐101(Al)−NH2 metal‐organic framework (MOF) is a water‐tolerant and selective solid Lewis acid catalyst for dihydroxyacetone isomerization to lactic acid. The Lewis acidic MIL‐101(Al)−NH2 catalyst promoted a high lactic acid selectivity of 91 % at 96 % dihydroxyacetone conversion at 120 °C in water. The reaction proceeded by temperature and/or MIL‐101(Al)−NH2 MOFs mediated dihydroxyacetone dehydration to pyruvaldehyde. Subsequently, the MIL‐101(Al)−NH2 facilitated rehydration of the pyruvaldehyde to lactic acid. The Lewis acidic MIL‐101(Al)−NH2 catalyst was stable and reusable four times without any decrease in catalytic performance.