Locking Photosensitizers into Staggered-Stacking and DNA-Interlocked Metal–Organic Frameworks for Outstanding CO 2 Photoreduction Activity

Photosensitizers (PSs) play crucial roles in photocatalysis by efficiently harvesting light and facilitating photoinduced charge transfer. However, whether they are applied in a homogeneous solution or immobilized on catalysts, PSs are prone to deactivation through leaching or desorption, leading to a significant decline in photocatalytic performance. Herein, two highly photoactive metal-organic frameworks (MOFs) denoted as NWUM-Cd-s and NWUM-Cd were constructed from Cd(II) ions, 4,4',4''-nitrilotribenzoic acid (H₃TCA), and a classic [Ru(bpy)₃]²⁺ PS via cocrystallization. These MOFs can firmly lock the [Ru(bpy)₃]²⁺ PS through the structural characteristics of DNA-like double-helix and "···ABABA···" dislocation stacking. This prevents the PS from deactivating during the photocatalytic process, which enables these MOFs to exhibit excellent photocatalytic activity and long-term cycling stability in the model CO₂ photoreduction reaction. The CO production rate of interpenetrated NWUM-Cd-s (13.9 mmol g^-1 h^-1) is 5.3 times that of dislocated monolayer NWUM-Cd (2.6 mmol g^-1 h^-1). In situ characterizations and theoretical calculations reveal that the interpenetrated structure of NWUM-Cd-s significantly enhances the separation of photogenerated charges, which in turn reduces the overall reaction energy barrier and promotes electron-proton transfer cooperativity, thus leading to more outstanding photoactivity than that of NWUM-Cd. This work demonstrates unprecedented staggered stacking and DNA-like interlocking strategies to lock PSs in catalysts, thereby tackling the long-standing challenges in traditional photocatalysis of low light utilization efficiency, PS deactivation, and slow charge transfer.