Pd/DUT-5 for mild and selective hydrogenation of nitrile butadiene rubber

Pd/DUT-5 is an efficient catalyst for NBR hydrogenation to HNBR. • High hydrogenation activity was achieved under mild conditions. • Metal-support interactions stabilize electron-enriched Pd δ+ species. • Pd δ+ species enhance catalytic activity and chemoselectivity. • DFT reveals low-barrier heterolytic H 2 activation at Pd δ+ –μ 2 O - sites. Hydrogenated nitrile butadiene rubber (HNBR), produced via the selective hydrogenation of nitrile butadiene rubber (NBR), has attracted considerable interest because of its excellent overall performance. However, the development of efficient and selective catalytic systems for NBR hydrogenation under mild conditions remains challenging, particularly when both activity and cost-effectiveness are required. Herein, Pd nanoparticles were immobilized on the Al-based metal-organic framework DUT-5, and the influences of Pd precursor salts and pretreatment conditions on catalytic hydrogenation performance were systematically investigated. The results show that using Pd(OAc) 2 as the precursor in combination with relatively low reduction temperatures promotes the formation and stabilization of electron-enriched Pd δ+ species through metal-support interactions, leading to excellent low-temperature activity and good reusability, with the hydrogenation degree remaining 94.5% after three cycles. Density functional theory calculations using C 2 H 4 as a model substrate further reveal that Pd δ+ sites cooperatively interact with μ 2 O - moieties to facilitate H 2 activation and subsequent hydrogen transfer through a heterolytic cleavage pathway with reduced energy barriers. These results provide a mechanistic basis for the efficient hydrogenation of NBR under mild conditions. Overall, this work demonstrates an effective and economical strategy for HNBR production and offers new insights into the design of highly active and chemoselective catalysts for NBR hydrogenation. Download: Download high-res image (205KB) Download: Download full-size image