Pillar-Layered Porous Metal–Organic Frameworks with Co<sub>2</sub>N<sub>2</sub>O<sub>8</sub> Clusters and Tetragonal Ligands for CO<sub>2</sub> Conversion
Lulu Wang, Jinmiao Wang, Ruixue Wu, Feng Shao, Dongmei Zhang, Xia Zhang, Chuanbin Fan, Yuhua Fan
Abstract
Converting CO 2 to valuable chemicals and fuels is a viable method to establish a carbon-neutral energy cycle in the environment. Metal–organic frameworks (MOFs), characterized by dispersed active sites, high porosity, etc., have displayed a great application prospect in the electrochemical/chemical CO 2 reduction reaction (CO 2 RR) process. Herein, we proposed a one-step production to establish a series of pillar-layered porous MOFs, [Co 2 (L)(bimb)] n (MOF 1 ) and [Co 4 (L) 2 (bidpe) 2 ] n (MOF 2 ) [H 4 L = 5′-(4-carboxyphenyl)-(1,1′:2′,1″-terphenyl)-4,4′,4″-tricarboxylic, bimb = 1,4-bis(imidazol-1-yl)-butane, bidpe = 4′-bis(imidazolyl) diphenyl ether], for preferential conversion of CO 2 via ligand adjustment and increase of active sites’ density. According to single-crystal X-ray diffraction studies, [Co 2 (L)(bimb)] n exhibits pillar-layered binuclear 3D frameworks with a 2,4,6-linked 3-nodes new topology structure, while [Co 4 (L) 2 (bidpe) 2 ] n displays pillar-layered tetranuclear interspersed networks with a 4,6-linked 2-nodes fsc topology structure through a ligand adjustment strategy. Meanwhile, the pillar-layered structure of the MOFs with abundant active sites is conducive to mass diffusion and benefits the conversion of CO 2 . MOFs 1 – 2 exhibit good electrocatalytic activity for CO 2 RR in 0.5 M KHCO 3 solution. Especially, the current density of MOF 2 generated at −0.90 V (vs. RHE) reaches −81.6 mA·cm –2, which is 3.1 times higher than that under an Ar atmosphere. In addition, MOFs 1 – 2 can be used as a heterogeneous catalyst for chemical conversion of CO 2 . The results are expected to provide inspiration for rational design to develop stable and high-efficiency MOF-based electrocatalysts for CO 2 RR.