Loading Ultrafine PdIr Clusters on Amine-Functionalized ZEO-1 Zeolite to Boost Catalytic Activity for Formic Acid Dehydrogenation at Room Temperature

Anchoring and stabilizing finely dispersed Pd-based alloy nanoparticles on porous substrates holds a highly promising strategy for developing efficient heterogeneous catalysts for hydrogen release from formic acid (FA, HCOOH), a unique liquid organic hydrogen carrier due to its high hydrogen content, low toxicity, ambient stability, and versatile obtainability. Herein, an extra-large-pore zeolite, ZEO-1, was synthesized and subsequently amine-functionalized using 3-aminopropyltriethoxysilane to obtain an NH2-ZEO-1 substrate. Ultrafine bimetallic PdIr clusters were then immobilized on its surface via a facile coreduction method. The as-prepared PdIr/NH2-ZEO-1 features abundant surface-exposed active sites, enhanced CO resistance, favorable FA adsorption ability, and improved H2 desorption kinetics in the FA dehydrogenation reaction. As a result, optimized Pd0.9Ir0.1/NH2-ZEO-1 exhibits an initial turnover frequency of 2610 h–1 at 298 K. Kinetic isotope effect measurements demonstrate that C–H bond cleavage is the rate-determining step, and isotopic labeling confirms the participatory role of H2O in the catalytic cycle. Further mechanistic studies identify HCOO* as a dominant surface intermediate over both Pd/NH2-ZEO-1 and PdIr/NH2-ZEO-1 catalysts.