A step‐growth strategy to grow vertical porous aromatic framework nanosheets on graphene oxide: Hybrid material‐confined Co for ammonia borane methanolysis

Abstract

AbstractThe rational synthesis of a two‐dimensional (2D) porous aromatic framework (PAF) with a controllable growth direction remains a challenge to overcome the limitation of traditional stacked 2D materials. Herein, a step‐growth strategy is developed to fabricate a vertically oriented nitrogen‐rich porous aromatic framework on graphene oxide (V‐PAF‐GO) using monolayer benzidine‐functionalized GO (BZ‐GO) as a molecular pillar. Then, the confined Co nanoparticle (NP) catalysts are synthesized by encapsulating ultra‐small Co into the slit pores of V‐PAF‐GO. Due to the high nitrogen content, large specific surface area, and adequate slit pores, the optimized vertical nanocomposites V‐PAF‐GO provide abundant anchoring sites for metal NPs, leading to ultrafine Co NPs (1.4 nm). The resultant Co/V‐PAF‐GO catalyst shows an extraordinary catalytic activity for ammonia borane (AB) methanolysis, yielding a turnover frequency value of 47.6 min−1 at 25°C, comparable to the most effective non‐noble‐metal catalysts ever reported for AB methanolysis. Experimental and density functional theory studies demonstrate that the electron‐donating effect of N species of PAF positively corresponds to the low barrier in methanol molecule activation, and the cleavage of the O–H bond in CH3OH has been proven to be the rate‐determining step for AB methanolysis. This work presents a versatile step‐growth strategy to prepare a vertically oriented PAF on GO to solve the stacking problem of 2D materials, which will be used to fabricate other novel 2D or 2D–2D materials with controllable orientation for various applications.