Synthesis and Characterization of Tungstophosphoric Acid/Pentaethylenehexamine/ZrSBA-15 and Its Use in the Selective Oxidation of Benzyl Alcohol under Solvent-Free Conditions

A layer‐by‐layer deposition strategy was employed for the immobilization of tungstophosphoric acid (HPW) onto a pentaethylenehexamine (PEHA)‐grafted ZrSBA‐15 framework to a give HPW/PEHA/ZrSBA‐15 composite. The resulting composite was characterized by XRD, SEM, TEM, FTIR, thermogravimetric analysis, N2 sorption, and X‐ray photoelectron spectroscopy, and these methods showed that the composite was stable in polar environments. These properties were attributed to the method of preparation, which ensured that a dense and stable array of HPW was encapsulated within the pores of PEHA‐modified ZrSBA‐15. In the H2O2‐mediated oxidation of benzyl alcohol, the 25 % HPW/PEHA/ZrSBA‐15 catalyst exhibited high selectivity (>99 %) for benzaldehyde. Moreover, the oxidation reaction was performed under solvent‐free conditions, and the catalyst was recycled several times with negligible loss in selectivity and conversion. This HPW‐based catalyst was also efficient at selectively oxidizing other benzylic and alkyl alcohols to the corresponding aldehydes. A layer‐by‐layer deposition strategy was used for the preparation of a tungstophosphoric acid/pentaethylenehexamine/ZrSBA‐15 composite. This recyclable material was stable at high temperatures and in polar solvents, and it exhibited excellent catalytic properties (84.7 % conversion, >99 % selectivity) in the selective oxidation of benzyl alcohol (BnOH) to benzaldehyde (BzH).