Confinement of ultrasmall Pd nanoparticles by layered covalent triazine frameworks for semihydrogenation of acetylene

Highlights: • The ultrasmall Pd NP were synthesized via the pore confinement effect of CTFs. • N atoms and the pore confinement effect of CTFs facilitate the catalytic activity. • The process mechanism of selective hydrogenation of acetylene was investigated. Acetylene hydrogenation is an important reaction in the petrochemical industry, the key is to develop efficient and selective catalyst. In this work, a highly crystalline layered covalent triazine frameworks (CTFs) with excellent thermal stability was used as carbon support to immobilize ultrasmall Pd nanoparticle for semihydrogenation of acetylene. Downsizing the particle sizes were realized by dual-solution assisted precursor mixture and using H₂ instead of NaBH₄ as reducing agent. The pore confinement effect of CTFs and the electronic intercalation from N atoms play key roles in improving the catalytic activity and stabilizing the Pd nanoparticles. The Pd/CTFs-H₂ catalyst exhibits 100% acetylene conversion and 99.9% ethylene selectivity at 250 °C and space velocity of 110,000 h⁻¹. The life test (>150 h), cycle test and chemical stability test demonstrated the long-term stability of the Pd/CTFs-H₂. The process mechanism of selective hydrogenation of acetylene in this catalyst is investigated by the in-situ infrared spectra.