Functionalizing carbon nitride with heavy atom-free spin converters for enhanced 1O2 generation

Carbon nitride as a metal-free conjugated polymer exhibits an intriguing prospect for the design of advanced photosensitizers for singlet oxygen (O-1(2)) generation. However, the intersystem crossing (ISC) process is quite insufficient in carbon nitride, limiting the O-1(2) generation. Here, we report a facile and general strategy to confined benzophenone as a heavy atom-free spin converter dopant in carbon nitride via the facile copolymerization. With proper energy level matching between the heavy atom-free spin converter and various ligands based on carbon nitride precursors, the proper combination can decrease the singlet-triplet energy gap (Delta EsT) and hence generate O-1(2) effectively. Due to its significant and selectivity for O-1(2) generation, the as-prepared carbon nitride-based photosensitizer shows a high selective photooxidation activity for 1,5-dihydroxy-naphthalene (1,5-DHN). The product yield reached 71.8% after irradiation for 60 min, which was higher than that of cyclometalated re complexes (53.6%) in homogeneous photooxidation. This study can broaden the application of carbon nitride in the field of selective heterogeneous photooxidation due to simple operation, low cost, and high efficiency, making it a strong candidate for future industrialization. (C) 2018 Elsevier Inc. All rights reserved.