Steric hindrance effect induced photopurification of styrene oxide over surface modified polymeric carbon nitride

The key of photopurification, a bran-new technique for substance purification, is selective mineralization by surface modification of photocatalyst. CN/NV-PCN, nitrogen vacancies (NV) and cyano groups (–CN) co-modified polymeric carbon nitride (PCN), selectively photomineralize benzaldehyde (BZ) in industrial styrene oxide (SO) production solution. NV, special O2 adsorption sites, guarantee the activation of O2 to H2O2. –CN, substitutes for hydrogens in terminal amines (–NH2), inhibit H2O2 randomly decomposing to •OH on –NH2 sites. NV and –CN adjust the electronic distribution on triazine ring and H to reinforce π-π interaction and O···HN bond between PCN and SO, narrowing the space between benzene ring and N3C site, in which the steric hindrance effect hinders H2O2 reducing to •OH by e- on N3C site. •OH can only produce at the adsorption sites of BZ, which results the selective mineralization of BZ. This work provides not only a modification method of PCN for selective oxidation reaction, but also a bran-new technique for removing homogeneous trace impurities in natural or industrial products.