Two-Dimensional Covalent Organic Frameworks Thin- Films as Photodetectors and Catalyst Host

Bag, Saikat (2024) Two-Dimensional Covalent Organic Frameworks Thin- Films as Photodetectors and Catalyst Host. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Saikat Bag (19RS041)) 19RS041.pdf - Submitted Version Restricted to Repository staff only Download (27MB)

Abstract

The physicochemical properties of crystalline polymers are greatly influenced by the degree of crystallinity and the orderliness of crystallites. However, achieving controlled crystallization of covalent organic frameworks (COFs) thin films with long-range order remains challenging. Recent research has focused on manufacturing COF thin films due to their potential in applications requiring rapid charge and mass transport. Large-area films with ordered pore channels and oriented crystalline domains are ideal for nano-filtration, electronic devices, and electrocatalysis. It is crucial to control the orientation of COF layers relative to a substrate to investigate charge migration. Various synthesis methods, such as direct, interfacial, and solvothermal approaches, have been developed for COF thin film construction. However, these methods often produce COF thin films that are not sufficiently uniform or planar for precise charge transport in device fabrication. Therefore, fabricating homogeneous COF thin films with high crystallinity, porosity, and uniform thickness on desired substrates is crucial for advanced applications in devices and heterogeneous catalysis. We have developed a synchronized crystallization methodology to synthesize COF thin films with thicknesses ranging from 300±20 nm to sub-10 nm. This process precisely controls the nucleation and molecular morphology of COF crystallites, leading to the formation of homogeneous thin films. We have also explored the growth mechanisms of these films on various substrates with different wettability. Additionally, we constructed optoelectronic devices to study the charge transport properties of COF thin films. Using chiral induction crystallization, we synthesized homochiral enantiopure COF films from achiral precursors and embedded a bioinspired catalyst into the chiral COF scaffold, creating a heterogeneous asymmetric catalytic platform.

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