Insights into the roles of metallic and coordinatively unsaturated cobalt sites in efficient 1,5-pentanediol production

Herein, the conversion of tetrahydrofurfuryl alcohol (THFA) and furfuryl alcohol (FAL)—hydrogenation products of furfural (FUR)—to 1,5-pentanediol (1,5-PDO) is investigated using a mixed metal oxide catalytic system composed of CoO x , MgO, and Al 2 O 3 . Different types of active sites are analyzed to establish correlations between catalyst structure and performance. Upon reduction, CoO forms the metallic species Co 0 and coordinatively unsaturated Co 2+ near O vacancies (OVs). These Co 2+ Lewis acid sites adsorb ether and hydroxyl O atoms from FAL and THFA, thereby weakening or cleaving the C2–O1 bond via coordination interactions. Simultaneously, H activated at the Co 0 sites undergoes spillover to the adsorbed intermediates, promoting hydrogenolysis and 1,5-PDO generation. At higher reduction temperatures, catalytic activities for both FAL and THFA transformations are enhanced due to the increase in the number and proximity of Co 2+ /OV sites, which favor strong dual-site adsorption via the η 2 -(O1, O2) coordination mode. In the case of FAL, this higher concentration of Co 2+ /OV sites also promotes higher selectivity toward 1,5-PDO. MgO provides basic sites that enhance strong reactive molecule adsorption probably via deprotonation, whereas Al 2 O 3 increases surface area and thus catalytic activity. Although the use of FAL as the reactant results in significantly higher productivity as compared to the case of THFA (FAL: 30.6 mmol 1,5-PDO g cat. −1 h −1 vs. THFA: 0.3 mmol 1,5-PDO g cat. −1 h −1 ), this higher productivity is achieved with the loss of 1,5-PDO selectivity, which is considerably lower (selectivity from FAL: 45.9 % vs. selectivity from THFA: 81.8 %). • Upon reduction, CoO forms Co 0 and coordinatively unsaturated Co 2+ near O vacancies. • Higher number of Co 2+ /O vacancy sites enhance both activity and selectivity. • DRIFTS reveals dual-site FAL/THFA binding and geometry-dependent activation. • Increased Co 0 content improves the hydrogenation capacity of the catalyst. • MgO enhances adsorption strength; Al₂O₃ increases catalyst surface area.