Bifunctional covalent triazine frameworks based on Ti-ON bonds for micropollutants removal: Effects of 3D extended structure and electron transport bridges

Abstract

Adsorption-photocatalysis technology enables the enrichment of pollutants and the regeneration of materials, which is expected to control long-lasting organic micropollutants (OMPs) in water. In particular, taking the comprehensive advantages of composites to simultaneously improve the adsorption and photocatalytic performance is currently worth considering. Therefore, a kind of Ti/MDCTF composite with specific and strong chemical bonds (Ti-ON bonds) was synthesized by a facile approach. Compared with pristine MDCTF, 30 %-Ti/MDCTF showed an increased saturated adsorption capacity (440.56 μmol/g) and a 5.6-fold increase in photocatalytic degradation kinetic (0.315 h−1). It was comfirmed by homogenous surface diffusion model (HSDM) that the adsorption kinetics were controlled by the intra-particle diffusion. Additionally, 30 %-Ti/MDCTF exhibited a high photocatalytic regeneration efficiency (91.7 %) after 7 rounds of degradation cycles in the natural water matrix. Experimental results and theoretical analysis collaboratively showed that the porous 3D extended structure with expanded interlayer spacing promoted the mass transfer and adsorption of OMPs. Furthermore, the Ti-ON bonds acting as electron transport bridges could promote the generation of photogenerated electrons from CTF and directional movement of them to TiO2 for efficient utilization. These findings reinforce the understanding of the adsorption-promoted 3D structure and site-specific regulation of directed electron-feeding, providing a feasible and convenient solution for the removal of OMPs in water.