Regulating ROS for highly efficient conversion of furfural to valuable organic acids in CoZnO catalyst

In pursuit of global carbon neutrality goals, catalytic upgrading of bio-based platform molecules like furfural has emerged as a crucial pathway for renewable chemical production. To address the issue of low selectivity in furfural oxidation due to over-oxidation, a CoZnO solid solution catalyst was developed by hydrothermally doping Co 2 + into ZnO in this study. The lattice distortion and oxygen vacancies in CoZnO not only provide a high surface area (62.15 m 2 /g) but also disperse Co sites for selectively activating peroxymonosulfate (PMS) to generate singlet oxygen ( 1 O 2 ). The high-rate selective oxidation was carried out at room temperature. Under optimized conditions (7 g/L PMS, 1.5 mol/L NaOH, 2.5 g/L catalyst), 99.3 % furfural conversion with 34.9 % furoic acid and 27.1 % maleic acid yields are achieved in 10 min. Quenching experiments and EPR analysis revealed that 1 O 2 , derived from the self-decomposition of PMS via electron transfer on Co sites, selectively oxidizes the aldehyde group of furfural while suppressing C-C bond cleavage. This contrasts with conventional radical-dominated pathways that cause over-oxidation. DFT calculations revealed that Co doping Sin ZnO, indicated by shifts in d-band centers and increased spin polarization, enhances PMS adsorption and singlet oxygen generation. The proposed oxidation pathway (furfural → furoic acid → 5-hydroxy-furan-2(5 H)-one → maleic anhydride → maleic acid) is supported by HPLC-MS identification of key intermediates. This work provides a ROS-regulation strategy for biomass valorization, with broad applicability to furan derivatives under mild aqueous conditions. • CoZnO catalyst with lattice distortion enhances PMS activation and ¹O₂ generation. • 99.3 % furfural conversion achieved with high yields of furoic acid (34.9 %) and maleic acid (27.1 %) in 10 min. • Singlet oxygen (¹O₂) selectively oxidizes furfural by suppressing over-oxidation and C-C bond cleavage. • DFT and HPLC-MS validate a furfural oxidation pathway driven by Co-doped ZnO and ROS regulation.