Covalent organic frameworks (COFs) show great promise as heterogeneous photocatalysts, but they have not yet been explored for asymmetric photocatalysis, which is important for the sustainable production of pharmaceuticals and fine chemicals. We report here a pair of twofold interpenetrated 3D COFs adopting a rare (3,4)-connected ffc topology for photocatalytic asymmetric reactions by imine condensation of rectangular and trigonal building blocks. Both COFs containing a photoredox triphenylamine moiety are efficient photocatalysts for the cross-dehydrogenative coupling reactions and asymmetric a-alkylation of aldehydes integrated with a chiral imidazolidinone catalyst. Under visible-light irradiation, the targeted chiral products are produced in satisfactory yields with up to 94% enantiomeric excess, which are comparable to those of reported reactions using molecular metal complexes or organic dyes as photosensitizers. Whereas the COFs became amorphous after catalysis, they can be recrystallized through solvent-assisted linker exchange and reused without performance loss. This is the first report utilizing COFs as photocatalysts to promote enantioselective photochemical reactions.

The metal−organic framework (MOF) HKUST-1 with a tbo topology serves as an archetypal tunable and isoreticular framework platform for targeting desired applications, but the design and synthesis of tbo-covalent organic frameworks (COFs) remains a formidable challenge. Here we demonstrate the successful use of reticular chemistry as an appropriate strategy for the design and deliberate construction of COFs with a tbo topology. The judicious selection of the perquisite planar building blocks, 4-connected square tetramine of porphyrin and 3-connected trigonal trialdehydes of triphenylamine, allows the condensation of two tbo-COFs, the first examples of COFs with a tbo topology. The resulting COFs both crystallize in the cubic Pm3̅ space group and adopt a non-interpenetrated open framework, in which each tritopic linker connects to three square units forming a truncated T d -octahedron and occupies the alternating triangular faces of the truncated octahedron. Owing to the presence of two different types of photoredox-active moieties, the two COFs can be efficient heterogeneous photocatalysts for the oxidative hydroxylation of arylboronic acids and the reductive defluoroalkylation of trifluoromethyl aromatics with alkenes. The present finding will provide an impetus to examine the potential of tbo-COFs as a new platform for engineering multifunctional materials via expansion and functionalization of building blocks.

A direct method has been developed for iodine-mediated thiolation of naphthols/naphthylamines and arylsulfonyl hydrazides through the formation of C-S bond and cleavage of S-N/S-O bonds. In this transformation, a range of valuable thioethers are easily achieved in moderate to good yields.

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The design and development of robust and porous supported catalysts with high activity and selectivity is extremely significant but very challenging for eco-friendly synthesis of fine chemicals and pharmaceuticals. We report here the design and synthesis of highly stable chiral Zr­(IV)-based MOFs with different topologies to support Ir complexes and demonstrate their network structures-dependent asymmetric catalytic performance. Guided by the modulated synthesis and isoreticular expansion strategy, five chiral Zr-MOFs with a flu or ith topology are constructed from enantiopure 1,1′-biphenol-derived tetracarboxylate linkers and Zr6, Zr9, or Zr12 clusters. The obtained MOFs all show high chemical stability in boiling water, strongly acidic, and weakly basic aqueous solutions. The two flu MOFs featuring the dihydroxyl groups of biphenol in open and large cages, after sequential postsynthetic modification with P­(NMe2)3 and [Ir­(COD)­Cl]2, can be highly efficient and recyclable heterogeneous catalysts for hydrogenation of α-dehydroamino acid esters with up to 98% ee, whereas the three ith MOFs featuring the dihydroxyl groups in small cages cannot be installed with P­(NMe2)3 to support the Ir complex. Incorporation of Ir-phosphorus catalysts into Zr-MOFs leads to great enhancement of their chemical stability, durability, and even stereoselectivity. This work therefore not only advances Zr-MOFs as stable supports for labile metal catalysts for heterogeneous asymmetric catalysis but also provides a new insight into how highly active chiral centers can result due to the framework topology.

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