Construction of NH2-MIL-101(Fe)/g-C3N4 hybrids based on interfacial Lewis acid-base interaction and its enhanced photocatalytic redox capability

Good interfacial bonding is an important factor to improve the photocatalytic activity of heterojunctions. In this work, a novel hybrid composed of NH2-MIL-101(Fe) and carboxylated g-C3N4 (CCN) was synthesized by a facile hydrothermal method based on interfacial Lewis acid-base interaction. By carboxylating the surface of g-C3N4 bulks, the surface acidic center -COOH is constructed, which can interact with the basic center -NH2 on the surface of NH2-MIL-101(Fe). As a result, a good interface binding and electron channel between them are formed, thus accelerating the separation of photogenerated electron-hole pairs and improve the photocatalytic activity of hybrids. The maximum ciprofloxacin degradation efficiency over 15% NH2-MIL-101(Fe)/CCN was 94% within 120 min under visible light irradiation. h+ and •OH are the main active species in the ciprofloxacin degradation process. In addition, the reduction efficiency of Cr(Ⅵ) over 10% NH2-MIL-101(Fe)/CCN reached 76% within 60 min, which was 2.71 and 1.62 times higher than pure CCN and NH2-MIL-101(Fe). The addition of ammonium oxalate can effectively enhance the Cr(Ⅵ) reduction efficiency by accelerating the dynamic process of the electron-hole pairs separation. The photocatalytic mechanism for ciprofloxacin degradation and Cr(Ⅵ) reduction over NH2-MIL-101(Fe)/CCN hybrid was proposed.