Environmentally friendly and innovative design of ZIF-67 and lignin modified composites for efficient catalytic transfer hydrodeoxygenation of lignin-related phenols†

Exploring lignin depolymerization and modification can yield high-value chemicals and liquid fuels, thereby enhancing resource utilization efficiency and alleviating pressure caused by energy shortages. In this paper, lignin-based carbon materials (Co-ZIF@KL-1 and Co-ZIF@KL-2) loaded with a metal–organic framework (ZIF-67) on kraft lignin biochar (KL) were prepared using two different methods (In situ method and traditional immersion method). In addition, catalysts with Co metal loaded on KL biochar (Co@KL) and ZIF-67 catalyst were also prepared for comparison with the above two different Co-ZIF@KL-1 and Co-ZIF@KL-2 catalysts. These catalysts were all applied to the hydrodeoxygenation (HDO) of guaiacol. Among them, the Co-ZIF@KL-1 catalyst exhibited the highest catalytic activity with 94.53% conversion of guaiacol and 83.86% selectivity of cyclohexanol under the optimal reaction conditions of 240 °C, 2.0 MPa N₂, and 4 h. The superior catalytic performance can be attributed to its high surface area, strong stability, and appropriate acidic sites. Based on the distribution of catalytic products, pathways for the guaiacol HDO reaction are hypothesized. In general, ZIF materials and lignin composites offer substantial value for advancing biomass catalytic conversion in the future.