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Dibenzo[ g , p ]chrysene can be viewed as a constrained propeller-shaped tetraphenylethylene with reduced curvature and has been utilized to construct dual-pore kagome covalent organic frameworks (COFs) with tightly packed two-dimensional (2D) layers owing to its rigid and more planar structural characteristics. Here, we introduce 2D COFs based on the node 4,4',4″,4‴-(dibenzo[ g , p ]chrysene-2,7,10,15-tetraphenyl)tetraamine (DBCTPTA) featuring extended conjugation compared to the dibenzo[ g , p ]chrysene-3,6,11,14-tetraamine (DBCTA) node. We establish two exceptionally crystalline imine-linked 2D COFs with a hexagonal dual-pore kagome structure based on the DBCTPTA core. The newly synthesized thienothiophene (TT) and benzodithiophene (BDT)-based DBCTPTA COFs show a tight stacking behavior between adjacent layers. Furthermore, we obtained an unprecedented, interpenetrated electron-donor/acceptor host-guest system with an electron-donating BDT DBCTPTA COF synthesized in situ with the soluble fullerene derivative [6,6]-phenyl-C 61 -butyric acid methyl ester (PCBM) serving as molecular acceptor. The BDT DBCTPTA COF@PCBM film shows a much shorter amplitude-averaged PL lifetime of 7 ± 2 ps compared to 30 ± 4 ps of the BDT DBCTPTA COF film, indicating the light-induced charge transfer process. The successful in situ formation of interpenetrated donor-acceptor heterojunctions within 2D COFs offers a promising strategy for establishing D-A heterojunctions in diverse framework materials with open channel systems.

Covalent organic frameworks (COFs) offer remarkable versatility, combining ordered structures, high porosity, and tailorable functionalities in nanoscale reaction spaces. Herein, we report the synthesis of a series of isostructural, photoactive Wurster-type COFs achieved by manipulating the chemical and electronic nature of the Wurster aromatic amine building blocks. A series of donor-acceptor-donor (D-A-D) Wurster building block molecules was synthesized by incorporating heteroaromatic acceptors with varying strengths between triphenylamine donor groups. These tailored building blocks were integrated into a 2D COF scaffold, resulting in highly crystalline structures and similar morphologies across all COFs. Remarkably, this structural uniformity was also achieved in the synthesis of homogeneous and oriented thin films. Steady-state photoluminescence revealed a tunable red-shift in film emission exceeding 100 nm, demonstrating effective manipulation of their optical properties. Furthermore, photoelectrochemical studies exhibited a doubled current density (8.1 µA cm-2 at 0.2 VRHE) for the COF with the strongest acceptor unit. These findings highlight the potential of these D-A-D COFs in photoelectrochemical water splitting devices and pave the way for further exploration of structure-property relationships in this promising class of photoactive materials., (© 2024 Wiley‐VCH GmbH.)

Hypoxia, as a crucial characteristic of cancer, has become an extremely significant direction for researchers to construct fluorescent probes for early diagnosis of tumors. Aggregation-induced emission fluorogens (AIEgens) possess many superior properties to those of conventional fluorophores due to aggregation-induced emission (AIE) features, such as a linear concentration-dependent increase in brightness, remarkable resistance to photobleaching, and the long-term tracking and imaging of cells. Constructing hypoxic response AIEgen-based probes will be very useful for the early diagnosis of tumors. Herein, several hypoxia-responsive probes based on AIEgens reported in the last three years are reported; these examples may lead to the construction of hypoxia-responsive AIE probes used for tumor hypoxia imaging in the future. In addition, typical, conventional hypoxia-responsive bioprobes are presented to further understand hypoxia-responsive fluorescent probes based on AIEgens., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A hypoxia-responsive fluorescence probe of amphiphilic PEGylated azobenzene caged tetraphenylethene (TPE) for tumor cell imaging is reported; it possesses excellent solubility in aqueous medium due to the easy formation of micelles by self-assembly. The fluorescence resonance energy transfer (FRET) process ensures that the fluorescence of the azobenene caged AIE fluorogen is quenched efficiently. When cultured with tumor cells, the azo-bond is reduced under hypoxia conditions and the fluorescence of AIE fluorogen recovers dramatically. Besides using UV light, NIR light can also be used as the excited light resource to generate the fluorescence due to the two-photon fluorescence imaging process., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)