(678d) Phosphorus-Substituted Zirconium Metal-Organic Frameworks with Bronsted Acidity and Their Versatility for Biomass Catalysis

The conversion of biomass feedstocks to produce platform chemicals is an important alternative to petroleum-based resources. Dienes are high-volume chemicals used as precursors in the productions of polymers. They also find applications as surfactants and lubricants. Synthesizing dienes by dehydra-decyclization of saturated furans using Bronsted acid catalysts appear as a promising strategy. Phosphorus-modified materials have been reported to have Bronsted acidity with exciting applications for catalysis of biomass, including phosphorus-supported zeolites and oxides. MOF-derived solid acids have also been applied in catalysis and separations. In this work, zirconium metal-organic frameworks with the UiO-66 topology with high stability were synthesized. We report the introduction of phosphonate and phosphonic acid moieties to both 1,4-benzenedicarboxylate (BDC) linker and biphenyl-4,4’-dicarboxylate (BPDC) synthesized by organic chemistry protocols to form UiO-66-PO₃H₂ and UiO-67-PO₃H₂ by a post-synthesis modification method_. The samples had their physicochemical properties characterized by different methods. While the P-MOFs retained crystallinity, porosity, morphology, and stability of the parent materials, phosphorus was successfully incorporated into the framework. Bronsted acidity was characterized by isopropanol dehydration and Hoffman elimination of amines. Catalytic activity was probed in the gas phase dehydra-decyclization of furans. The synthesized MOFs showed activity and selectivity to dienes, indicating their potential application as heterogeneous acid catalysts.