Light-induced synthesis of triazine N-oxide-based cross-linked polymers for effective photocatalytic degradation of methyl orange

Abstract

The scarcity of clean water and increasing environmental pollution are critical issues owing to the rapid development of industrialisation, population growth and long-term droughts. Research and development of robust photocatalysts is very important to treat recalcitrant organic dye wastewater. Porous organic polymers are favored as a new type of photocatalyst owing to their high specific surface area and porosity. Here, two novel 2D cross-linked polymers LCP-1 (Light-induced Cross-linked Polymer 1) and LCP-2 (Light-induced Cross-linked Polymer 2) were synthesized through light-induced click cross-coupling reaction. Starting from LCP-1 and LCP-2 as supports, the polymeric aromatic N-oxides (LCPO-1 and LCPO-2) were prepared through the reaction of the nitrogen-containing aromatic heterocycle and peroxyacetic acid at 333 K, respectively. The structure and morphology were studied by IR, solid-state ¹³C NMR, TEM and SEM. The polymeric aromatic N-oxides (LCPO-1 and LCPO-2) as organic metal-free photocatalysts showed great potential in the photodegradation of methyl orange (MO) in solution. The turn over number (TON) and the turn over frequency (TOF) of the catalysts varied and depended on the structures. For LCPO-1, the calculated TOF of the catalyst for the three cycles were determined, which were 4.83 × 10¹⁶, 2.50 × 10¹⁶ and 2.00 × 10¹⁶ molecules per g per s, while for LCPO-2 were 4.00 × 10¹⁶, 2.40 × 10¹⁶ and 1.67 × 10¹⁶ molecules per g per s, respectively.