New-fashioned MnOx/g-C3N4@ZIF-8 catalyst for the liquid-phase selective oxidation of toluene in the absence of solvent or additives†

A new-fashioned MnO_x/g-C₃N₄@ZIF-8 catalyst was synthesized by a co-precipitation method. It exhibited good catalytic performance in the liquid-phase selective oxidation of toluene in the absence of solvent or additives. Series characterization confirmed the doping of Mn in the catalyst and large specific surface area, which resulted in high catalytic activity and high target product selectivity. The optimal reaction was conducted at 180 °C for 2.0 h, with 0.1 g of catalyst and oxygen pressure of 1.0 MPa. The toluene conversion was 4.7%, the selectivity to benzaldehyde and benzyl alcohol (BAL + BOL), and benzoic acid (BAC) was 74.3%, and 18.2%, respectively. In addition, a possible oxidation reaction pathway was postulated. The catalyst has low cost and high selectivity to BAL + BOL, which is of great industrial importance for the highly selective production of BAL and BOL from toluene.