Ultrafine Palladium Nanoparticles Stabilized in the Porous Liquid of Covalent Organic Cages for Photocatalytic Hydrogen Evolution

Soluble covalent organic cages (COCs) were designed to comprise cryptand inner cavities and multiple metal-chelating sites on windows. The porous liquid formed by well-dispersed COCs in solution proves to be an excellent stabilizer for ultrafine palladium nanoparticles with a critical size of 1–3 nm using NaBH4 or methanol as a reductant. When transferring palladium nanoparticles stabilized in the porous liquid of COCs onto carbon nitride (g-C3N4), an efficient heterogeneous photocatalyst could be obtained to possess high catalytic activity for hydrogen evolution from water with long-term durability. This provides prospects for the application of porous liquids in various fields by combining advantages of homogeneous and heterogeneous attributes together.