Aquivion‐Based Spray Freeze‐Dried Composite Materials for the Cascade Production of γ‐Valerolactone

The development of multifunctional catalysts is a necessary step to effectively carry out one‐pot cascade reactions, such as that from furfural to γ‐valerolactone. This research effort faces the challenge posed by the intrinsic limit of how many kinds of catalytic sites a single material can bear. In this work, the application of Spray‐Freeze Drying (SFD) as a synthetic technique for the preparation of a wide range of innovative composite multi‐functional catalysts is reported. Herein we show that by the proper combination of Aquivion as a highly active Brønsted acid catalyst and metal oxides as both support materials and Lewis acids (LAS) enable to achieve highly unique efficient and effective dual acid composite catalysts that are able to carry out the cascade reaction from furfural to γ‐valerolactone. The dual catalytic system comprised of Aq/ZrO2 with 30 % polymer content prepared via spray‐freeze drying exhibited GVL yields of 25 % after only 2 h at 180 °C and a remarkably high productivity of 4470 μmolGVL gCat−1 h−1, one of the highest reported results. Mechanistic studies based on experimental and advanced characterisation and spectroscopic techniques, such as, SEM, TEM, 15N MAS NMR and 19F MAS NMR indicate that activity arises from the proper tuning of BAS/LAS (Brønsted Acid Site/Lewis Acid Site) acidic properties. Spray‐Freeze Drying synthesis allows the preparation of Aquivion‐based composite with highly accessible and tuned acidic properties. MAS NMR after 15N‐Pyridine adsorption revealed the role and abundance of the different acid sites. Aquivion/Zirconia catalysts showed, for the first time for this class of hybrid materials, the right combination of acid sites to promote the cascade synthesis of GVL, achieving highly competitive productivities.