Covalent organic framework (COF) monolayers, with atomically thin, ordered networks, and rich functionality, are widely studied due to their unusual structure/property relationships. However, synthesizing COF monolayer has remained an unmet challenge due to the difficulty of controlling reactions at the monolayer limit with large-scale uniformity. The identification and development of new reactions and polymerization conditions are critical for the further advancement of COF monolayer materials. Moreover, as one-molecule-thick a freestanding films, COF monolayer offers an ideal material system. Many advanced applications of COF monolayer have been explored in recent literature. This review provides an overview of the current state of precise synthetic strategies for COF monolayer, highlighting the advantages and limitations of different synthetic approaches and key challenges related to enhancing quality, and emphasizing the unique benefits of COF monolayer as both an ideal model system and for advanced applications.

Covalent organic frameworks (COFs) represent an emerging class of crystalline porous polymers with high porosity, good stability, and adjustable structure, and their excellent characteristics lay a solid foundation for electrocatalysis. This review systematically introduces the design principles of the catalytic sites in two-dimensional (2D) COF-based electrocatalysts and analyzes the relationship between 2D COF structure and their electrocatalytic performances. In particular, the recent progress in the field of 2D COFs as electrocatalysts is comprehensively summarized. Finally, we discuss the current shortcomings and challenges on tailoring 2D COF for high-performance electrocatalysts in details, and look forward to promoting more researches on 2D COF-based electrocatalysts.

Two-dimensional (2D) transition metal dichalcogenides (TMDCs)-based heterostructures open the door to fabricate various promising hybrid photodetectors, while it is still a challenge to achieve excellent and stable near-infrared (NIR) photoresponse. Here, a MoS₂–2DPI (2D-polyimide (2DPI)) heterojunction-based phototransistor (HPT) was fabricated. Near-infrared photodetection with excellent performance has been realized. This HPT exhibited a photoresponsivity of 390.5 A/W, a specific detectivity of 5.10 × 10¹² Jones, a photogain 1.04 × 10⁵, and a photoresponse rise and decay time of 400 and 430 ms (λ = 900 nm, P = 16.2 μW/cm²), respectively. It also shows a broadband wavelength response from 405 to 1,020 nm. This superior performance could be attributed to the strong near-infrared absorption and the type-II (staggered) band alignment which ensures efficient charge transfer from 2DPI to MoS₂. The face-to-face spatial configuration of MoS₂–2DPI heterostructures ensures efficient transfer of photoinduced carriers through the interface, electron and holes can be separated due to the large band offsets. This work presents a significant step for the manipulation of high-performance NIR photodetector of two-dimensional covalent organic polymer-sensitized monolayer TMDCs.

Unraveling the nature of complex condensed matter systems is of paramount importance in a variety of fields such as pharmacology and materials science. Here we report the synthesis, by the dynamic covalent chemistry (DCC), of a robust, continuous, and low-defect glassy covalent organic network (GCON). The direct imaging of the molecular structure clearly shows the amorphous nature of GCONs, which consists with the competing (nano) crystallite model, not Zachariasen continuous random networks (Z-CRN). Remarkably, the microscopic friction properties were measured on GCONs by atomic force microscopy (AFM), and the GCONs showed lower friction force in comparison with crystalline covalent organic frameworks (COFs).