Construction of 0D/2D Porphyrin-Based MOF-on-MOF Heterojunctions for Efficient Photocatalytic CO ₂ Reduction

Solar-driven CO 2 reduction into valuable chemicals/fuels is considered a promising strategy for mitigating the global energy and environmental crisis. Engineering MOF-on-MOF hybrid frameworks featuring sophisticated charge-transfer mechanisms has arisen to be a propitious policy for augmenting the photocatalytic performance of MOFs. In this work, a 0D/2D Mg/Sn-mediated porphyrin-based heterojunction hybrid was designed and synthesized. Importantly, the CO 2 -to-CO photoreduction efficiency for Mg/Sn-ZnTCPP MOF achieved 138.2 μmol·g –1 ·h –1, significantly surpassing that of the individual Mg-ZnTCPP MOF and Sn-ZnTCPP MOF. Experimental results revealed that the n–n type S-scheme heterojunction incorporated internal electric field direction with energy band bending at interfaces promotes the migration of photoexcited electrons and facilitates electron–hole separation, thus leading to superior photocatalytic activity. This study developed a facile method to construct MOF-on-MOF S-scheme heterojunction for achieving high-efficiency photocatalytic CO 2 conversion.