Covalent organic frameworks (COFs) are porous crystalline framework materials that are amenable to design and functionalization. Herein, an aggregation-induced emission monomer, 4,4′,4″,4‴-(ethene-1,1,2,2-tetrayl)­tetrabenzaldehyde (ETB), is used as a building block to react with an olefin linkage to construct sp2 carbon-conjugated COFs for exploring their electrochemiluminescence (ECL). The ECL efficiency of ETB immobilized in the COF framework is significantly improved by nearly 100 times without any exogenous co-reactants in aqueous solution, compared with the monomer aggregation state. This framework-induced ECL (FIECL) is attributed to the long-range orderly arrangement of COFs confining the rotation of ETB in the π-conjugated backbone, thereby effectively facilitating the electronic transfer for excited-state generation. Density functional theory calculations prove that the COFs have lower energy bands compared with the monomers, so that electron transfer can be accelerated within frameworks to obtain a much stronger FIECL signal. This FIECL strategy will greatly expand the broad application prospects of COFs in organic optoelectronics.

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Nanomaterials with enzyme mimetic activity have attracted extensive attention, especially in the regulation of their catalytic activities by biomolecules or other polymers. Here, a covalent organic framework (Tph‐BT COF) with excellent photocatalytic activity is constructed by Schiff base reaction, and its mimetic oxidase activity and peroxidase activity is inversely regulated via single‐stranded DNA (ssDNA). Under light‐emitting diode (LED) light irradiation, Tph‐BT exhibited outstanding oxidase activity, which efficiently catalyzed oxidation of 3,3′,5,5′‐tetramethylbenzidine (TMB) to produce blue oxTMB, and ssDNA, especially those with poly‐thymidine (T) sequences, can significantly inhibit its oxidase activity. On the contrary, Tph‐BT showed weak peroxidase activity, and the presence of ssDNA, particularly poly‐cytosine (C) sequences, can remarkably enhance the peroxidase activity. The influence of base type, base length, and other factors on the activities of two enzymes is also studied, and the results reveal that the adsorption of ssDNA on the surface of Tph‐BT prevented intersystem crossing (ISC) and energy transfer processes to reduce 1O2 generation, while the electrostatic interaction between ssDNA and TMB enhanced Tph‐BT's affinity for TMB to facilitate the electron transfer from TMB to •OH. This study investigates multitype mimetic enzyme activities of nonmetallic D‐A conjugated COFs and demonstrates their feasibility of regulation by ssDNA.

The structural isomerism of the covalent organic framework (COF) has a significant effect on the electrochemiluminescence (ECL) performance. Herein, we report a pair of isomeric COFs, (TFPB-BD(OMe) 2 -H and TAPB-BD(OMe) 2 -H), based on the different directions of imine linkages and further conversion of the imine to the quinoline structure. The obtained two isomeric COFs with the same composition and similar structures exhibit dramatic differences in the photoelectrochemical and ECL fields. Indeed, TFPB-BD(OMe) 2 -H demonstrates robust ECL emission superior to that of TAPB-BD(OMe) 2 -H. The difference in ECL performance is due to the stronger polar interaction of TFPB-BD(OMe) 2 -H than that of TAPB-BD(OMe) 2 -H. The polarity is derived from the uneven charge distribution within the framework and enhances the electron interactions. In addition, the ordered conjugate skeleton provides high-speed charge transport channels for carrier transport. Therefore, the TFPB-BD(OMe) 2 -H presents a smaller band gap energy and stronger polarization interaction, which are more favorable to charge migration to achieve stronger ECL signals. Furthermore, we describe a convenient ECL sensor for detecting toxic As(V) with an outstanding detection property and ultralow detection limit. This work provides a guiding principle for the design and development of ECL organic luminophores.