▎ 摘　　要

The 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 degrees 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.