Rational engineering of MgNiP 2 O 7 and MgCoP 2 O 7 bimetallic pyrophosphate catalysts: selective activation of lignocellulosic cellulose for the sustainable production of levulinic acid

This study reports the synthesis of MgNiP₂O₇ and MgCoP₂O₇ via a conventional solid-state route with heat treatment up to 800 °C. The materials were characterised by XRD, FTIR and UV–vis spectroscopy, confirming the formation of pure monoclinic crystalline phases. UV–vis spectra reveal distinct electronic features associated with transition-metal d–d transitions, while FTIR analysis highlights characteristic pyrophosphate vibrational modes influenced by metal identity. The catalysts were evaluated for the conversion of Juncus effusus - derived cellulose to levulinic acid. MgCoP₂O₇ exhibited superior performance, achieving an optimal yield of 87.5% at 90 °C after 5 h, compared to 56.6% for MgNiP₂O₇. This enhanced activity is attributed to the favourable redox behaviour of the Co²+/Co³+ couple and efficient hydroxyl radical generation through a Fenton-type mechanism. Selectivity decreases under harsher conditions, indicating the need for further optimisation and detailed surface characterisation.