Interfacial Zn─O─Ti Sites for Efficient Photocatalytic Urea Synthesis from CO2 and N2.

Urea photosynthesis from CO2 and N2 has profound environmental and energy implications. However, the simultaneous activation of CO2 and N2, along with the promotion of C─N bond formation, remains a major challenge. Herein, the asymmetric interfacial sites (Zn─O─Ti) were engineered by building oxygen atom bridges between ZIF-8 and MIL-125 to enable efficient photocatalytic urea synthesis. The optimized Zn─O─Ti interface structure achieves a urea yield of 130 µmol g-1 h-1 in pure water and an apparent quantum yield of 5.52% at 350 nm, outperforming most materials reported for urea photosynthesis. Mechanistic studies reveal that Zn sites catalyze the conversion of CO2 to *CO species, while Ti sites adsorb and activate N2 to generate *NH-NH species. The asymmetric interfacial sites lower the energy barrier for the coupling of *CO and *NH-NH to form *CONH2 intermediates, thereby promoting urea photosynthesis. This work provides significant insights into designing interfacial asymmetric sites to facilitate photosynthetic organic chemicals for upgrading the nitrogen cycle.