Solvent-Induced Flower- and Cudgel-Shaped Porous Organic Polymers: Effective Supports of Palladium Nanoparticles for Dehalogenation in Net Water

Dehalogenation of aromatic halides is one of the most important reactions for detoxification of water ecosystems; at the same time the ability is inevitably tied to the dispersibility of catalyst in aqueous medium. Herein, we present aporous organic polymers containing hydrophilic urea groups (UPOPs) for effective immobilization of palladium nanoparticles (NPs) through a facile urea-forming condensation reaction. The urea groups not only serve as an intriguing linkage of organic framework, but also endows Pd@UPOPs outstanding dispersibility in H2O. The morphology of UPOPs have exerted important influence upon the size and dispersion of palladium NPs as well as their catalytic performances. The palladium NPs are well dispersed on the surface of UPOP-1 with an average size of 2.1 +/- 0.3 nm. In contrast, palladium NPs on UPOP-2 exhibit a dual size distribution with an average diameter of 2.0 +/- 0.4 and 4.2 +/- 0.4 nm. The dehalogenation reactions of chlorobenzene have demonstrated that Pd@UPOP-1 with flower-shaped morphology show higher catalytic activity, recyclability and stability than that of Pd@UPOP-2 with cudgel-shaped morphology. This work offers/supplies a new insight for the development of efficient catalytic systems based on porous organic polymers supported metal NPs in aqueous medium.