Orderly Layered Zr-Benzylphosphonate Nanohybrids for Efficient Acid-Base-Mediated Bifunctional/Cascade Catalysis

The development of functional metal-organic materials that are robust and active for bifunctional/cascade catalysis is of great significance. Herein, a series of mesoporous and orderly layered nanohybrids were synthesized for the first time through simple and template-free assembly of ortho-, meta-, or para-xylylenediphosphonates (o-, p-, or m-PhP) containing zirconium. It was found that m-PhPZr nanoparticles (20-50 nm) with mesopores centered at 7.9 nm and high Lewis acid-base site ratio (1:0.7) showed excellent performance under mild conditions (as low as 82 degrees C) in transfer hydrogenation of carbonyl compounds, including bioaldehydes and alcohols, with near quantitative yields and little Zr leaching. Isotopic labeling studies indicated the occurrence of direct hydrogen transfer rather than metal hydride route by bifunctional catalysis. Lewis acidic (Zr) and basic (PO3) centers of the heterogeneous catalyst were further revealed to play a synergistic role in one-pot cascade transformations, for example, of ethyl levulinate to g-valerolactone and glucose to 5-hydroxymethylfurfural.