Enhancing the catalytic performance of POM@MOF composite materials by controlled thermal modification

A novel and straightforward thermal activation strategy to enhance the catalytic performance of a polyoxometalate (POM)–metal–organic framework (MOF) composite in oxidative desulfurization (ODS) was developed and reported. A Keggin-type phosphomolybdic anion ([PMo₁₂O₄₀]³⁻, PMo₁₂) was successfully incorporated into the ZIF-67 framework to form the composite materials PMo₁₂@ZIF-67, which unexpectedly exhibited negligible catalytic activity under mild ODS conditions. Upon post-synthetic thermal treatment at just below the point of complete structural degradation (500 °C) under inert atmosphere, the resulting material (PMo₁₂@ZIF-67_500) underwent substantial textural and structural changes, including a fourfold increase in surface area, and a fivefold increase in micropore volume. These modifications translated into a dramatic improvement in catalytic performance, achieving up to 94 % sulfur removal from a multicomponent model diesel in only 2 h. The catalyst also demonstrated excellent reusability over four consecutive cycles without loss of activity or POM leaching. This work introduces for the first time a controlled thermal treatment route as an effective post-synthetic modification to activate otherwise inactive POM@MOF composites, paving the way for the development of robust and sustainable heterogeneous catalysts for fuel purification. • PM O12 @ZIF-67 composite material was prepared by a straightforward synthetic route. • Suitable post-synthetic thermal treatment induced effective structural modifications. • Thermally modified material at 500ºC was an efficient and sustainable catalyst for oxidative desulfurization reaction. • Promising strategy to develop much more efficient POM@MOF-based catalysts.