Structural design of covalent organic frameworks and their recent advancements in carbon capture applications: A review

Covalent organic frameworks (COFs) are an attractive subclass of porous solids due to their strong potential in various applications. The reticular chemistry behind COF design enables the achievement of desired functional properties. Additionally, the post-synthesis modification (PSM) of COFs is an effective method for tuning their skeleton architecture, chemical stability, and chemical interactions with guest molecules to enhance specific properties. However, the inherent challenges related to their chemical and thermal stability have limited their widespread use. Recently, various approaches for PSM on the pre-established covalent framework have been reported, providing an opportunity to tune the functional properties of COFs while maintaining and even strengthening their fundamental framework integrity and crystallinity. This review highlights recent advancements in synthesis strategies and PSM of COFs with enhanced stability and versatile functional properties. The discussion highlights different design approaches of COFs, such as the compatible reticular chemistry of their stronger covalent bonds and rigid building blocks and new innovative PSM techniques, including cross-linking and surface functionalization. Additionally, we explore the impact of these strategies on COF properties, such as porosity, chemical and thermal stability, and their surface chemistry, thereby expanding their practical applications. We provide a comprehensive overview of current advances in COF solids and performances in gas adsorption and separation applications, specifically for carbon capture and conversion, as well as in direct air capture (DAC) of CO₂. This review aims to offer insights into the future directions of COF research, focusing on developing robust and functional COFs that meet real-world carbon capture and utilization requirements.