Porous Aromatic Framework Nanosheets Anchored with Lewis Pairs for Efficient and Recyclable Heterogeneous Catalysis.

Lewis pairs (LPs) with outstanding performance for nonmetal-mediated catalysis reactions have high fundamental interest and remarkable application prospects. However, their solubility characteristics lead to instability and deactivation upon recycling. Here, the layered porous aromatic framework (PAF-6), featuring two kinds of Lewis base sites (N and N), is exfoliated into few-layer nanosheets to form the LP entity with the Lewis acid. After comparison with various porous networks and verification by density functional theory (DFT) calculations, the N atom in the specific spatial environment is determined to preferably coordinate with the electron-deficient boron compound in a sterically hindered pattern. LP-bare porous product displays high catalytic activity for the hydrogenation of both olefin and imine compounds, and demonstrates ≈100% activity after 10 successful cycles in hydrogenation reactions. Considering the natural advantage of porous organic frameworks to construct LP groups opens up novel prospects for preparing other nonmetallic heterogeneous catalysts for efficient and recyclable catalysis.