Ultrahigh Responsivity Photodetectors of 2D Covalent Organic Frameworks Integrated on Graphene

2D materials exhibit superior properties in electronic and optoelectronic fields. The wide demand for high-performance optoelectronic devices promotes the exploration of diversified 2D materials. Recently, 2D covalent organic frameworks (COFs) have emerged as next-generation layered materials with predesigned π-electronic skeletons and highly ordered topological structures, which are promising for tailoring their optoelectronic properties. However, COFs are usually produced as solid powders due to anisotropic growth, making them unreliable to integrate into devices. Here, by selecting tetraphenylethylene monomers with photoelectric activity, elaborately designed photosensitive 2D-COFs with highly ordered donor-acceptor topologies are in situ synthesized on graphene, ultimately forming COF-graphene heterostructures. Ultrasensitive photodetectors are successfully fabricated with the COF_ETBC-TAPT -graphene heterostructure and exhibited an excellent overall performance with a photoresponsivity of ≈3.2 × 10⁷ A W^-1 at 473 nm and a time response of ≈1.14 ms. Moreover, due to the high surface area and the polarity selectivity of COFs, the photosensing properties of the photodetectors can be reversibly regulated by specific target molecules. The research provides new strategies for building advanced functional devices with programmable material structures and diversified regulation methods, paving the way for a generation of high-performance applications in optoelectronics and many other fields.