The integration of Triazine-based porous organic polymer with bio-waste poplar catkin as water-floatable photocatalyst

Abstract

Floating photocatalysis material has a big advantage over powdery suspending one for deep purification of pollutants in colored wastewater, in consideration of its excellent flexibility, high light-harvesting, and convenient recycling in suspension solution systems. As a result, the design and synthesis of floating photocatalyst are of great importance. Herein, we concentrate on the preparation of metal-free triazine-based porous organic polymer (POP) as a visible-light photocatalyst on biomass waste poplar catkins (PCs) to construct a reusable floating photocatalysis system via a soft synthesis, that is, trigonal-symmetrical melamine (M) is coupled with triformylphloroglucinol (TFP) monomer to obtain photoactive conjugated POPM-TFP loaded on soft and light PC microfibers (Named as PC/POPM-TFP). When PC/POPM-TFP (20 mg) is floated on the polluted water, it can convert 100% Cr(VI) (50 mL, 10 mg/L) in 80 min into Cr(III) species which are then partly synchronously immobilized (56.9%) to lessen the rerelease of Cr element, or degrade 100% methylene blue (MB, 60 mL, 10 mg/L) after 100 min of visible-light irradiation. Moreover, the film-like flexible self-supporting PC/POPM-TFP also exhibits well catalytic activities and excellent reusability for multipurpose water purification under real natural conditions. The molecular oxygen in the solution gains electrons from PC/POPM-TFP to generate •O2–, which is involved in photoreduction of Cr(VI) besides photo-induced electrons, and mainly contributes to photooxidation degradation of MB. The proposal of floating PC/POPM-TFP not only avoids the risks to release metal ions into water during utilization, which will cause secondary pollution, but also provides an alternative method to overcome the limitations of powdery photocatalyst for recycling. Overall, this study assists the assembly of green floating photocatalysis systems to allow a versatile solid surface activation for establishing more energy efficient and robust catalysis process under visible light.