Coordination immobilization of palladium ions in the novel three-dimensional cerium porphyrin metal-organic framework for enhanced photocatalytic carbon dioxide reduction

Abstract

Although cerium metal-organic frameworks (MOFs) demonstrate superior photocatalytic performance compared to other materials in the family of MOFs, they still do not meet the necessary standards. The photocatalytic performance of the material was significantly enhanced by integrating modification strategies with the precious metal palladium, which further improved the performance of the palladium-modified cerium metal-organic framework. Here, we presented a novel three-dimensional palladium-porphyrin cerium metal-organic framework (Pd-Ce PMOFs) that uniformly encapsulates Pd²⁺ through stable N-Pd coordination bonds. This approach effectively addressed the common issues of uneven dispersion and instability found in palladium-modified photocatalysts. The optimized Pd-Ce PMOFs exhibited excellent photocatalytic performance for carbon dioxide reduction, achieving a CO yield of 191.24 ± 3 μmol g^-1 h^-1, which was 3.81 times higher than that of the original Ce PMOFs, with a selectivity of 98.13 %. Density functional theory (DFT) calculations indicated that Pd²⁺ served as a dual active site for the adsorption of carbon dioxide and its catalytic activation. This process reduced the energy barrier to 1.59 eV for the formation of the *COOH intermediate and facilitated efficient carrier migration. This work not only pioneers a stable three-dimensional Ce-Pd PMOFs structure but also promotes the use of palladium coordination modifications, thereby advancing the rational design of high-performance MOF-based photocatalysts for sustainable CO₂ conversion.

Keywords: Active adsorption sites; Carbon dioxide reduction; Ionic modifier; Metal-organic framework; Photocatalyst.