Closely Contacted Multi-Sulfides of Ag2S/ZnS/ZIS/In2S3: In Situ Synthesis From Ternary ZIF-8@MIL-68(In)@Ag-MOF and Visible-Light Photocatalytic Hydrogen Evolution

The multiple metal sulfides with closely contacted interface demonstrate superior photocatalytic activity due to the efficient charge transfer, excellent visible light response ability, and the ideal photocatalytic stability. In this paper, a ternary metal–organic frameworks (MOFs) (ZIF-8@MIL-68(In)@Ag-MOF) was designed as the precursor to precisely construct the multiple metal sulfides of Ag₂S/ZnS/ZIS/In₂S₃ through an in situ one-step sulfurization strategy. The sulfurization process was controlled to preserve the three-dimensional porous architecture of MIL-68(In), and the hollow hierarchical tubes were readily produced due to the sulfurization occurred inner and outer ternary MOFs simultaneously. In the process, the In₂S₃ was generated; firstly, then, the ZnS and Ag₂S was formed; meanwhile, the ZnIn₂S₄ (ZIS) was readily produced at the interface of ZnS and In₂S₃ because of the naturally metal ions exchange. The as-synthesized multiple metal sulfides (named as Z@M@A-t, where t represents the sulfurization time) were used in visible light–induced photocatalytic hydrogen generation. It is shown that the best hydrogen evolution rate is 794.83 μmol g⁻¹ h⁻¹ by Z@M@A-24, which values are evidently higher than that of the ternary MOF precursor. The electrochemical analyses were conducted to clarify the charge transfer route and the enhanced photocatalytic mechanism. It is proven that the closely contacted junction works well in the interface electron transfer. And, the good reusability of Z@M@A-24 heterostructure was also presented. The work highlights the prospect applications of multi-MOF-derived heterostructure for efficient hydrogen production under visible light irradiation.