Metal-Free Polydiacetylene-Functionalized Polymer for Photocatalytic Anionic and Cationic Dye Degradation and CO₂ Capture

It is important to tackle sustainability challenges using affordable, metal-free porous organic polymers. Herein, we report the synthesis of a visible-light-responsive, metal-free polydiacetylene-based conjugated covalent organic polymer (COP). This is accomplished by photopolymerizing its diacetylene monomer (DA) without the need for a chemical reaction initiator or byproducts. The visible light response and porosity of the PDA@COP are utilized for the photocatalytic degradation of individual dyes (MO, anionic & MB, cationic) and their mixture, as well as for CO2 capture applications. When exposed to relatively low-power blue light (12 W), the PDA@COP demonstrates photocatalytic degradation of 98% for MB and 84% for MO, with rate constants of 0.021 and 0.010 min–1 over a period of 180 min, respectively. In contrast, a binary mixture of the dye solutions (MO + MB) shows a degradation of 99.9% for MB and 88% for MO, with rate constants of 0.042 and 0.017 min–1 in just 100 min, respectively, due to the synergetic interchange of O2•– and •OH radicals. Moreover, the PDA@COP demonstrates remarkable recyclability. Additionally, the PDA@COP shows a CO2 uptake of 66.72 cm3·g–1 (2.72 mmol·g–1), which is a 3.45 times increase compared to DA.