The water shortage crisis, characterized by organic micropollutants (OMPs), urgently requires new materials and methods to deal with it. Although heteroatom doping has been developed into an effective method to modify carbon nanomaterials for various heterogeneous adsorption and catalytic oxidation systems, the active source regulated by intrinsic electron and spin structures is still obscure. Here, a series of nonmetallic element-doped (such as P, S, and Se) covalent triazine frameworks (CTFs) were constructed and applied to remove organic pollutants using the adsorption–photocatalysis process. The external mass transfer model (EMTM) and the homogeneous surface diffusion model (HSDM) were employed to describe the adsorption process. It was found that sulfur-doped CTF (S-CTF-1) showed a 25.6-fold increase in saturated adsorption capacity (554.7 μmol/g) and a 169.0-fold surge in photocatalytic kinetics (5.07 h–1), respectively, compared with the pristine CTF-1. A positive correlation between electron accumulation at the active site (N1 atom) and adsorption energy was further demonstrated with experimental results and theoretical calculations. Meanwhile, the photocatalytic degradation rates were greatly enhanced by forming a built-in electric field driven by spin polarization. In addition, S-CTF-1 still maintained a 98.3% removal of 2,2′,4,4′-tetrahydroxybenzophenone (BP-2) micropollutants and 97.6% regeneration after six-cycle sequencing batch treatment in real water matrices. This work established a relation between electron and spin structures for adsorption and photocatalysis, paving a new way to design modified carbon nanomaterials to control OMPs.

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Defect engineering of nanomaterials has emerged as a promising approach to improve their performance for pollutant removal. However, various nanomaterial defects play variant roles in environmental applications. It is still a challenge to construct multiple defects of composite materials into advantageous aggregates to deal with complicated matrix pollution. In this work, we investigated a series of three-dimensional defectoptimized aerogels (3D DOAs) of graphene oxide (GO) with a covalent triazine framework (CTF) for improved adsorption and photoregeneration performance via tailoring duet carbon and nitrogen defects. Using chemical reduction, carbon defects in GO were gradually repaired and nitrogen defects in CTF were created simultaneously. The carbon defect engineering generated additional nonpolarized electron-depleted sites in GO of 3D DOA for increased adsorption capacities (2417 μmol/g for benzophenone, 2209 μmol/g for 4-hydroxybenzophenone, 1957 μmol/g for 2,2′,4,4′-tetrahydroxybenzophenone). Meanwhile, increasing nitrogen defects of the CTF in 3D DOA would produce midgap states for an extended absorption range of visible light and increased photocatalytic activity to remove adsorbed pollutants. The enhanced adsorption and the superior photocatalytic regeneration soundly corroborated that the performance of 3D DOA was improved effectively by the defect optimization strategy. Moreover, the high stability of 3D DOA and its practical usage were verified in a real water matrix with a 7-day cycle test. The present work highlights an approach of defect optimization for development of a solardriven, self-regenerative adsorbent for water purification with high efficiency.

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