Research Progress on Fluorene-Based Covalent Organic Frameworks and Metal-Organic Frameworks

The rapid development of flexible electronic technology is driving profound changes in the material system. In this revolution, organic materials have gained unprecedented development space due to their structural tunability, biocompatibility, and mechanical flexibility. However, their practical applications have long been limited by core bottlenecks, including low carrier mobility, poor environmental stability, and performance degradation caused by disordered molecular arrangements. In this context, covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) are high-dimensional organic materials that provide nanoscale frameworks for excitons and electronics, exhibiting inorganic-like optoelectronic behaviors and performances. Fluorene-based organic semiconductors are a key class of organic materials that have been widely explored and applied across flexible devices, including organic light-emitting diodes (OLEDs), organic photovoltaics (OPVs), and others. It is emerging to explore the organic high-dimensional materials for accelerating flexible electronics facing organic intelligence. Given the outstanding features of MOFs and COFs, incorporating fluorene-based molecular fragments into these materials may yield superior performance. In the review, we summarize fluorene-based topological designs, synthesis, and characterization of COFs and MOFs, along with their application in adsorption, sensing, photocatalysis, and electrocatalysis. Finally, we discuss future challenges, such as scalability and carrier mobility improvement, and opportunities, providing insights for high-performance flexible electronic applications.