Mn-based catalysts derived from the alkaline hydrolysis-calcination treatment of Mn-BTC for efficiently catalytic toluene combustion

Green two-step alkaline hydrolysis–calcination yields hollow MnO x spheres from Mn-BTC. • H 3 BTC is efficiently recovered and reused, yielding high atom economy. • MBN 1.0 –500 hosts a MnO 2 /Mn 5 O 8 biphasic heterostructure with O vacancies. • MBN 1.0 –500 achieves low-temperature toluene oxidation: T 90  = 196 °C and E a  = 29.4 kJ mol −1 . • DFT and in situ DRIFTS show the interface lowers vacancy energy, boosts toluene activation. Tuning the oxygen species reactivity of manganese-based catalysts is critical for the efficient catalytic oxidation of volatile organic compounds (VOCs). Herein, a series of hollow spherical manganese oxide catalysts (MBN₁.₀-T) were synthesized via a two-step alkaline hydrolysis-calcination strategy using Mn-BTC as the precursor. Notably, the organic ligand trimesic acid (H₃BTC) can be efficiently recovered and reused after alkaline treatment, endowing the synthesis route with excellent atom economy. Among the obtained catalysts, MBN₁.₀-500, featuring a MnO₂/Mn₅O₈ biphasic heterostructure, delivers outstanding low-temperature catalytic performance for toluene oxidation with T₉₀ as low as 196 °C and an apparent activation energy of 29.4 kJ mol −1 . Comprehensive characterizations combined with DFT calculations reveal that the abundant heterointerfaces between MnO₂ and Mn₅O₈ significantly reduce the oxygen vacancy formation energy and enhance toluene adsorption and activation, thereby promoting the generation of reactive oxygen species and accelerating lattice oxygen mobility. In situ DRIFTS confirms that the degradation pathway of toluene proceeds as toluene → benzyl alcohol → benzaldehyde → benzoate → maleic anhydride → CO₂ and H₂O. This work not only provides a sustainable strategy for constructing high-performance MnOₓ catalysts with abundant oxygen vacancies, but also highlights the great potential of ligand recovery for industrial application. Download: Download high-res image (120KB) Download: Download full-size image