CC3 porous organic cage crystals and membranes for the non-thermal plasma catalytic ammonia synthesis

Abstract

Ammonia is considered a basic building block for fertilizers. Also, it is an economically efficient and technologically suitable solution for energy storage and transportation. Non-thermal plasma-driven catalysis powered by renewable energy is considered as a green alternative to the conventional Haber-Bosch process for ammonia synthesis. The main challenge in this electron-mediated route is the low ammonia synthesis production, given the plasma-induced decomposition of the freshly generated ammonia during the reaction. Herein we report the plasma-assisted ammonia synthesis in a dielectric barrier discharge reactor packed with CC3 crystals, a prototypical porous organic cage, and a molecular-sieve membrane fabricated from the same CC3 material. The CC3 crystals delivered the highest ammonia synthesis rate (0.06 μmol min−1 m−2) compared to other microporous catalysts such as zeolite (SAPO-34) and metal-organic frameworks (ZIF-8, ZIF-67) (below 0.02 μmol min−1 m−2). The CC3 porous cage with well-defined octahedral crystal geometry provides partial protection while the CC3 membrane offers both adsorption and separation effects for the freshly formed ammonia from its in-situ decomposition, securing an excellent ammonia synthesis rate of 20.3 μmol min−1 m−2. The findings from this work unfolds novel insights into rational designs of advanced porous catalyst and membrane for plasma-driven catalytic ammonia synthesis in a sustainable and efficient way.