The lignin-first biorefinery strategy could produce bio-based phenols from the extraction and depolymerization of native lignin in lignocellulosic biomass. Herein, we report an effective Lewis acid-promoted delignification and production of monophenolic compounds in birch sawdust assisted by microwave heating without external hydrogen for the first time. The screening of different metal triflates revealed that Fe(OTf)₃ was best for the delignification and depolymerization of birch sawdust. Without the addition of a Lewis acid, the yield of monophenolic compounds was 10.5 wt% (based on the lignin content in birch sawdust), while it increased significantly to 32.9 wt% with the addition of Fe(OTf)₃ (0.0276 g) under the identical conditions (190 °C, 1 h), which demonstrated the catalytic COC bond scission promoted by Fe(OTf)₃. Simultaneously, the delignification degree also rose sharply from 32.6 wt% to 47.5 wt%. This work demonstrated the efficient Fe(OTf)₃-induced delignification and depolymerization of lignin in birch sawdust to obtain a high yield of monophenolic compounds without external hydrogen assisted by microwave heating, representing a novel advance in the “lignin-first” biorefinery field.

木质素优先生物精炼策略可以通过木质纤维素生物质中天然木质素的提取和解聚生产生物基酚。在此，我们首次报道了在没有外部氢的情况下借助微波加热辅助的桦木锯末中有效的路易斯酸促进的去木质作用和单酚类化合物的生产。对不同金属三氟甲磺酸酯的筛选表明，Fe（OTf）₃最适合桦木锯末的脱木质素和解聚反应。在不添加路易斯酸的情况下，单酚类化合物的产率为10.5 wt％（基于桦木锯末中木质素的含量），而在添加Fe（OTf）_{3的情况下}，单酚类化合物的收率显着提高至32.9 wt％。（0.0276克）的相同的条件（190℃，1个小时），这表明催化℃在Ò被Fe（OTF）促进C键断裂₃。同时，脱木素度也从32.6重量％急剧上升至47.5重量％。这项工作证明了由Fe（OTf）₃诱导的桦木锯末中木质素的脱木质素和解聚反应可实现高产率的单酚类化合物，而无需借助微波加热而获得外部氢气，这代表了“木质素优先”生物精炼领域的一项新进展。