Synergy between interface-induced dual active sites ZIF-67@Co-TCTB for enhanced visible-light photocatalytic nitrogen fixation

Photocatalytic nitrogen reduction reaction (PNRR) provides a sustainable pathway for green ammonia synthesis, but still faces challenges such as high photogenerated carrier complexation rate and difficulty in N 2 activation. In this study, ZIF-67@Co-TCTB (ZC-250) MOF-on-MOF composites were prepared by liquid-phase synthesis, aiming at dual active site synergy and interfacial charge behavior modulation to enhance visible light nitrogen fixation performance. Structural and compositional analyses (FT-IR, XRD and XPS) indicate that the composite possesses both Co–N and Co–O coordination environments, and introduces N–Co and C O active sites on the surface, which effectively enhances the N 2 adsorption and activation capacity. Diffuse reflectance spectroscopy (DRS), Mott–Schottky (M–S) and steady-state photoluminescence (PL) characterization revealed that the photogenerated electrons migrated from ZIF-67 to Co-TCTB, which facilitated the interfacial charge separation, and then efficiently reduced the surface adsorbed N 2 to NH 4 + . Under the condition of no sacrificial agent, the NH 4 + yield of ZC-250 was as high as 199.73 μmol g −1  h −1 , which was an 8-fold enhancement over that of pure ZIF-67, and showed good stability after four cycles. This study provides a new material design strategy for the construction of MOF-based nitrogen fixation photocatalysts with synergistic active centers and regulated interfacial electronic behavior.