Tailoring Porous Organic Frameworks for Metal Free Photo and Electrocatalysis

Basak, Ananda (2025) Tailoring Porous Organic Frameworks for Metal Free Photo and Electrocatalysis. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Ananda Basak (20RS009)) 20RS009.pdf - Submitted Version Restricted to Repository staff only Download (13MB)

Abstract

Covalent Organic Frameworks (COFs), promising in photo- and electrocatalysis due to their crystalline porosity, modular synthesis, and tunable electronic structures. However, their catalytic efficiency is often limited by poor charge separation, low conductivity, and restricted accessibility of active sites. High surface area alone does not guarantee effective catalysis unless paired with efficient mass transport and well-distributed, accessible active sites. In many COFs, uniformly narrow pores and dense stacking can limit substrate diffusion and reduce catalytic turnover. To address this, frameworks must be engineered with hierarchical or open-channel porosity, facilitating faster reactant diffusion and product release. Furthermore, building blocks' spatial arrangement influences charge mobility and catalytic activity. Extended π-conjugation and donor–acceptor linkers can promote better light absorption and charge separation in photocatalysis, while ordered stacking and oriented growth can improve electron transport in electrocatalytic systems. We synthesized photochemically active COFs from organic dye units. β-keto-enamine-based COFs served as polymeric pigments for visible-light-driven, metal-free C–H borylation of azines, showing broad functional group tolerance. Azo functionalized COF achieved the highest efficiency due to its large surface area, broad absorption, and low band gap, enabling improved charge transfer and radical generation. These COFs displayed high stability and reusability. We have also designed and synthesized macrocycle-based porous organic polymers. Imine and β-keto-enamine-based polymers have been synthesized to verify their performance. Later on, we designed triazatrinaphthalene triamine-derived COFs for electrocatalytic nitrate reduction to ammonia. Six COFs have been synthesized to verify performance with respect to the functional group. The COFs showed excellent durability over multiple cycles and 40 hours of continuous operation.

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