Strategies for Perfect Confinement of POM@MOF and Its Applications in Producing Defect-Rich Electrocatalyst

Polyoxometalate encapsulated by metal–organic framework (POM@MOF) hybrid is an ideal precursor for electrocatalysts because it provides a homogeneous catalyst system with a flexible synergistic effect. However, controlling its fine structures to activate the derived catalyst after pyrolysis remains a challenge. The uniformly distributed carbon-defect tungsten oxides on the 3D carbon matrix were synthesized by using phospho-tungstic acid confined in HKUST-1 (PA@HKUST-1) as the precursor. By choosing ethanol as the solvent, the framework of PA@HKUST-1 was retained integrally and each pore of HKUST-1 kept intact even with holding the PA molecule inside. The well-organized structure of PA@HKUST-1 facilitated to offer a highly distributed metal source, and further transform into defect-rich catalyst. The average size of the resulting WO_xC_y/C catalysts was 1.5 nm, which was similar to a single molecule of PA. The WO_xC_y/C catalysts exhibited superior activity in the methanol oxidation reaction after being platinized due to the enhanced resistance to CO poisoning, which is also confirmed by DFT. This finding suggests a new route to design and achieve the defect-rich catalyst with controllable size.