When covalent organic frameworks meet metals: From opportunities toward applications

Abstract

Porous materials, particularly covalent organic frameworks (COFs), exhibit well-defined porosity, tunable structural features, and high chemical and thermal stability. These intrinsic properties render COFs highly promising candidates for the rational design of efficient functional materials, thereby attracting significant interest across diverse scientific and engineering disciplines. Nevertheless, pristine COF frameworks often suffer from an insufficient density of active sites and functional moieties, thereby constraining their practical performance. Accordingly, the incorporation of metal components into COF architectures has emerged as a promising strategy to enhance their functionalities. In this review, we introduce a novel classification scheme grounded in the interaction strength between metal species and COFs, which enables a systematic organization of existing metal-modified COF materials. This framework facilitates an in-depth analysis of this intriguing class of materials by elucidating the intrinsic relationships and distinctions among different metal-modified COF materials from the perspective of metal-COF interaction strength, thereby advancing the fundamental understanding of their structure-property correlations. Furthermore, we comprehensively summarize recent progress in metal-modified COF materials with respect to applications including adsorption and separation, photocatalysis, electrocatalysis, energy storage, sensing, and biomedicine. Emphasis is placed on structural design principles, synthetic methodologies, characterization techniques, and how different metal-modified COF materials influence reaction pathways and underlying mechanisms. Ultimately, the current challenges and future research directions pertaining to metal-modified COF materials are critically discussed.