Rational design of functional covalent organic frameworks for the oxygen and Carbon Dioxide reduction reactions

Abstract

Porous materials have developed significantly due to their remarkable properties and wide-ranging applications, such as gas capture, gas separation, optoelectronics, ion detection, catalysts, and energy storage. Within the category of porous polymers, covalent organic frameworks (COFs) have garnered increasing attention since their successful synthesis in 2005.
COFs consist of lightweight elements interconnected by covalent bonds, imparting excellent chemical and thermal stability. Furthermore, they possess precisely integrated extended structures with periodic skeletons and ordered pores. COFs exhibit well-defined alignment of π building units in atomic layers and segregated arrays of π columns in their frameworks. These elegant π skeletons form the foundation for structural design, while the 1D channels offer controllable sizes, shapes, and environments. Consequently, the diverse skeleton, ordered porous structure, pre-designable functions, and high chemical stability make COFs highly suitable for applications in gas/molecular adsorption, energy storage, electro-/photo-catalysis, conversion, semiconductors, and Li-ion batteries. Additionally, the pyrolysis of COFs into functional carbons represents a simple and efficient strategy to enhance conductivity.
Nevertheless, direct pyrolysis of COFs often leads to carbons with aggregated skeletons and collapsed pores. Therefore, further exploration is required to synthesize structures of COFs precisely for electrocatalysts in electrocatalysis reactions. Furthermore, the rational design, specific functionalization, and meticulous synthesis of COF structures are crucial for preparing high-crystalline COF materials and improving their application properties.
In this thesis, COF-derived carbons were designed through direct pyrolysis, featuring a unique core-shell framework for constructing high-density active sites. The optimized COF-derived carbons demonstrated exceptional electrocatalysis performance. However, achieving precise control over dimensions, structure, skeleton polarity, pore environments, functional groups, and defects is necessary to explore the elaborate synthesis of COFs and their applications in electrochemical energy storage and conversion systems. Therefore, a class of functional COF material with high crystallinity was successfully prepared through rational structural design and precise regulation, exhibiting excellent performance in electrocatalytic reduction. Specifically, the synthesis strategy involved skeleton engineering, dimension control, and catalytic density modulation to investigate the relationship between structure and electrocatalysis performance.

Date of Award	Jul 2024
Original language	English
Awarding Institution	University of Nottingham
Supervisor	Jun He (Supervisor), Svenja Hanson (Supervisor), George Zheng Chen (Supervisor) & Gaofeng Zeng (Supervisor)