Synergistic Engineering of Pyrene–Thiazolothiazole-Based Donor−π–Acceptor Conjugated Microporous Polymers with Heteroatom Embedding for Efficient Visible-Light Photocatalyst for Organic Dye Degradation

Abstract

Water pollution caused by organic dyes poses a significant threat to ecosystems and human health, underscoring the urgent need for sustainable degradation methods. We report two donor−π–acceptor conjugated microporous polymers (CMPs), Pyr-Ph-TzTz and Pyr-Th-TzTz, assembled from pyrene (Pyr) donors, phenyl or thiophene π-bridges, and thiazolothiazole (TzTz) acceptors. Precursors [4,4′,4″,4‴-(pyrene-1,3,6,8-tetrayl)tetrabenzaldehyde (Pyr-Ph-4CHO) and 5,5′,5″,5‴-(pyrene-1,3,6,8-tetrayl)tetrakis(thiophene-2-carbaldehyde) (Pyr-Th-4CHO)] were synthesized via electrophilic bromination and Suzuki–Miyaura coupling with 4-formylphenylboronic acid (PFPBA), and 5-formyl-2-thienylboronic acid (5-FTBA); respectively. Pyr-Ph-4CHO and Pyr-Th-4CHO were each subjected to a one-pot condensation reaction with dithiooxamide, yielding robust, thermally stable CMPs─Pyr-Ph-TzTz and Pyr-Th-TzTz─with amorphous frameworks and surface areas of 37 and 20 m2 g–1, respectively. UV–vis spectra reveal narrow band gaps of 2.02 eV for Pyr-Ph-TzTz CMP and 2.39 eV for Pyr-Th-TzTz CMP. Pyr-Ph-TzTz CMP exhibits markedly enhanced charge separation, as evidenced by pronounced PL quenching and ultraviolet photoelectron spectroscopy (UPS) analysis. Both CMPs adsorb rhodamine B (RhB) rapidly (equilibrium in 30 min; 55% removal by Pyr-Ph-TzTz CMP, 90% by Pyr-Th-TzTz CMP) and degrade it under visible light, achieving 96% (k = 0.0545 min–1) and 39% (k = 0.00341 min–1) removal, respectively. Radical scavenging and EPR identify •OH as the primary active species. Remarkably, Pyr-Ph-TzTz CMP retains >90% activity after five cycles, highlighting its promise for solar-driven dye removal.