Diversified functional applications of flexible metal-organic frameworks

Flexible metal-organic frameworks (FMOFs) are widely emerging soft porous materials with tunable functionalities in spite of their poor mechanical robustness. Opening and closing of pores (also known as 'breathing') in response to physical or chemical stimuli are the key features of these FMOFs. The extent of flexibility of MOFs depends on various factors such as type of organic linkers, pore geometry, secondary building units (SBUs), gas molecules, solvent or other stimuli. The flexibility and dynamic behavior induced by external stimuli generate the intriguing diverse applications across various fields. Besides, recent progress in designing, tuning, controlling, and properties investigations of FMOFs are discussed briefly. Through comprehensive characterization and evaluation based on selected recent reports, this work also provides insights to harnessing the versatility of FMOFs for diverse research advancements in drug delivery, guest capture & release, proton transfer, catalysis, gas storage & separation, sensing and luminescent-based applications. Flexible metal-organic frameworks (FMOFs) are widely emerging porous materials with tunable functionalities, despite their poor mechanical strength. Their key feature is "breathing" or "pore opening and closing" phenomena in response to stimuli. Their flexibility induced by external stimuli makes FMOFs uniquely suited for advanced functional materials. Recent research highlights their diverse applications in drug delivery, catalysis, gas storage, sensing, and more. • Organic linkers and synthetic strategies of flexible metal-organic frameworks (FMOFs) are briefly summarized. • Stimuli-induced breathing or 'pore opening/closing behaviors in specific FMOFs are reviewed. • Tuning and controlling of FMOFs have been emphasized. • Diversified applications of FMOFs have been comprehensively mentioned. • Current challenges and future prospects for FMOFs are provided.