Highly Water-Stable and Efficient Hydrogen-Producing Heterostructure Synthesized from Mn_0.5Cd_0.5S and a Zeolitic Imidazolate Framework ZIF-8 via Ligand and Cation Exchange

Developing highly water-stable zeolitic imidazolate frameworks (ZIFs) for visible-light-driven photocatalytic hydrolysis is important and challenging. Herein, the Type II heterojunction catalyst Mn_0.5Cd_0.5S@ZIF-8 and its derivatives (including MCS@ZIF-8-Mn, MCS@ZIF-8-Br, and MCS@ZIF-8-MB) were successfully constructed using a facile strategy. Through dual postsynthetic ligand and cation exchange (PSE) treatments of Mn(Ac)₂·4H₂O and 4-bromo-1H-imidazole for ZIF-8, the hydrogen production efficiency of the MCS@ZIF-8-MB heterojunction catalyst can reach 5.450 mmol·g^-1·h^-1 and remain at 97.11% after 9 h of the stability test. Construction of heterojunctions can effectively improve the hydrogen production performance of Mn_0.5Cd_0.5S while maintaining excellent water stability. X-ray photoelectron spectroscopy results show that upon successful construction of the MCS@ZIF-8-MB heterojunction an interface forms between the surface of MCS and ZIF-8-MB, effectively weakening the photocorrosion of MCS. Density functional theory calculations also indicate that the induction of Mn can increase the electronic states of p and d orbitals near the Fermi level of ZIF-8, suggesting that Mn(II) attracts more electrons than Zn(II). This provides more powerful theoretical evidence for the electron cloud shift from the electron donor S^2- to Mn²⁺.