Reticular Imine‐Linked Coordination Polymers Based on Paddlewheel Diruthenium/Dirhodium Nodes: Synthesis and Metal‐Site Dependent Photocatalytic Reduction of CO₂

The paddlewheel‐type dimetal core ([M 2 ]) is a ubiquitous motif in the nodes in coordination polymers (CPs) and metal‐organic frameworks (MOFs). However, their preparation has relied on ligand‐substitution‐labile metal ions owing to challenges associated with crystallization. Consequently, examples featuring ligand‐substitution‐inert metal ions, such as Ru or Rh, are scarce. This study presents the synthesis of novel reticular imine‐linked CPs incorporating the paddlewheel‐type diruthenium(II, II) ([Ru 2 II,II ]; 1‐Ru ) or dirhodium(II, II) ([Rh 2 II,II ]; 1‐Rh ) subunits. The synthetic approach involved a Schiff base dehydration condensation reaction between p ‐formylbenzoate‐bridged [Ru 2 II,II ] or [Rh 2 II,II ] precursors (i. e., CHO−Ru and CHO−Rh , respectively) and 2,5‐dimethyl‐1,4‐phenylenediamine in a 1 : 2 ratio. The catalytic activities of 1‐Ru and 1‐Rh for the photochemical reduction of CO 2 in a heterogeneous system depended on the metal site. The 1‐Ru system exhibited exceptional selectivity, generating 3.0×10 4 μmol g −1 of CO after 24 h of irradiation, whereas the 1‐Rh system generated a lower amount of CO (3.2×10 3 μmol g −1 ). The catalytic activity of 1‐Ru ranked with that of all relevant catalytic systems. This study paves the way for the exploration of [Ru 2 II,II ]‐ or [Rh 2 II,II ]‐based polymers with open metal site‐dependent functional properties.