Additive-Free Hydrogen Generation from Formic Acid Boosted by Amine-Functionalized Imidazolium-Based Ionic Polymers

Catalytic dehydrogenation of formic acid (FA) is an efficient approach to store and release hydrogen in fuel-cell-based hydrogen economy; it is still a daunting challenge to the design and synthesis of the additive-free heterogeneous catalytic systems. In this contribution, we present an amine-functionalized main-chain imidazolium-based ionic polymer (ImIP-1) for boosting additive-free hydrogen generation from FA. The ultrafine palladium nanoparticles (NPs) with uniform dispersion over ImIP-1 were readily obtained through simple anion exchange between chloride in ImIP-1 and tetrachloropalladate and subsequent reduction with NaBH4. The palladium NPs are synergetically stabilized by coordination interaction and electrostatic effect from ImIP-1. The amine groups in the host backbone of ImIP-1 serve as basic sites to accelerate the cleavage of O-H bond in FA. The catalytic system shows outstanding catalytic activity, high stability, and excellent recyclability in additive-free heterogeneous FA dehydrogenation under mild conditions. The initial TOF values at 50 and 25 degrees C are as high as 1593 and 356 h(-1), respectively, which are 10 times higher than those in its counterpart without amine groups. The impressive catalytic performance ranks it among the state-of-the-art of those in heterogeneous catalytic systems based on supported palladium NPs.