Transition Metal Ion‐Directed Coordination Polymers with Mixed Ligands: Synthesis, Structure, and Photocatalytic Activity for Hydrogen Production and Rhodamine B Degradation

Abstract

Three mixed‐ligand transition metal coordination polymers with the formula of {[CuI2CuII(tpt)2(L)]·15H2O}n (1) and {[M2(H2O)5(tpt)(L)]·6H2O}n [M = Ni for 2 and Co for 3; tpt = 2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine and L = 3,3'‐disulfonyl‐4,4'‐biphenyldicarboxylate] were hydrothermally synthesized by varying the cheap paramagnetic metal ions and used as photocatalysts for hydrogen evolution from water splitting and rhodamine B (RhB) degradation. Single‐crystal structural determinations reveal that 1 is a robust pillared‐layer framework with unusual 72‐membered {Cu6(tpt)6} macrocycle‐based layers supported by tetratopic L4– connectors. Both 2 and 3 are isostructural (4 4) sheets with octahedral NiII and CoII ions extended by ditopic L4– and tpt linkages, in which the third pyridyl group of tpt is capped by pentahydrated metal ions. Due to the narrowed bandgap and good charge transport of the mixed‐valence CuI/II centers, 1 exhibits improved dual‐functional catalytic activities than 2 and 3 with the visible‐light‐driven hydrogen evolution rate and RhB degradation efficiency up to 588 μmol·g–1·h–1 and 72 % after 180‐minute irradiation. These interesting results indicate the importance of the metal ions and the dimensionality of the coordination polymers on the activity of the non‐Pt coordination polymer photocatalytic systems.