Research paperUse of aligned triphenylamine-based radicals in a porous framework for promoting photocatalysis

•First report of Ca-based FIR-29 for Mannich photocatalysis in high yields.•FIR-29 shows hexagonal channels with aperture of 16 Å and large BET of 2061 m2/g.•Consecutive π···π stacking of TBPA radicals induces optimal PET for photocatalysis.•The heterogeneous photocatalyst FIR-29 remains catalytic activity after 3 cycles.

The Ca-MOF FIR-29 is synthesized and exhibits a honeycomb lattice of hexagonal channels with an aperture of ∼16 Å, giving a BET surface area of 2061 m2 g−1. The consecutive slipped π···π stacking interactions of photoactive tris((4-carboxyl)phenylduryl)amine (TCPA) groups on the surface of hexagonal channels makes it an effective photocatalyst for catalyzing the typical Mannich photocatalysis, forming β-tetrahydroisoquinolne ketones in high isolated yields. Catalytic activity for FIR-29 is about 2.7 times enhancement over that for mesoporous DUT-63 consisted of discrete TCPA groups without any intermolecular interaction. This is mainly due to the fact that the rigid compact stacking of tri([1,1′-biphenyl]-4-yl)amine (TBPA) is conducive to form stable TBPA radical, and is optimal for electron or energy transfer to expedite the reactivity of sp3 carbon atoms and allow higher photocatalytic conversion.

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