Wenjiao Li, Shupeng Guo, Heqin Guo, Yaqiong Su, Yong Xiao, Minggui Lin, Litao Jia, Debao Li
High Resolution Image Download MS PowerPoint Slide The selective oxidation of n -butane to maleic anhydride (MA) over the vanadium phosphorus oxide (VPO) catalyst stands as a prominent example of industrial selective alkane functionalization. Despite its commercial maturity, the ambiguous relationship between the catalytic performance and vanadium valence states (V ox ) or surface lattice oxygen (O S-L ) persists in generating debate and uncertainty regarding the identity of the active sites in VPO catalysts. Herein, we reconcile this debate by demonstrating that the catalytic efficiency is governed by valence-state-dependent O S-L rather than by merely the O S-L content. Using time-resolved H 2 -TPR experiments, we successfully distinguished two distinct types of valence-state-dependent O S-L: V 5+ -O S-L (O S-L related to the V 5+ phase) and V 4+ -O S-L (O S-L related to the V 4+ phase). Their specific functions were then elucidated through a combination of in situ reactant-specific H 2 -TPR experiments (utilizing n -butane, 1,3-butadiene, or propylene as probes) and 18 O-isotopic labeling studies. The results clearly demonstrate that V 5+ -O S-L is identified as the site for the initial hydrogen abstraction from n -butane, while V 4+ -O S-L facilitates the crucial epoxidation step to form MA. Furthermore, by employing CeO 2 as a modulator, we precisely tune the V 5+ -O S-L /V 4+ -O S-L ratio through the formation of Ce–O–V bonds, as evidenced by the X-ray absorption near edge (XANES) and extended X-ray absorption fine structure (EXAFS) analysis. An optimal V 5+ -O S-L /V 4+ -O S-L ratio for MA synthesis is 2.22–2.82; otherwise, it would be more conducive to a nonselective reaction. This work introduces a novel design paradigm for the development of high-performance VPO catalysts, offering a comprehensive framework for the rational design of heterogeneous oxidation catalysts via precise control of valence-specific oxygen chemistry.