Single-atom Rh based bipyridine framework porous organic polymer: A high active and superb stable catalyst for heterogeneous methanol carbonylation

A novel Rh based porous composed N polymer with hierarchical pore, high surface area and high thermal stability (Rh-POL-2BPY) was successfully obtained by impregnation of Rh-2(CO)(4)Cl-2 solution of dichloromethane. And based on Rh species as the most active carbonylation site, Rh-POL-2BPY was selected as a catalyst applied in heterogeneous methanol carbonylation system and behaved excellent carbonylation activity (TOF approximate to 1400 h(-1)) under 195 degrees C, 2.5 MPa, higher than the corresponding homogeneous system without acetic acid. In addition, contrast to the most reported unstable heterogeneous methanol carbonylation systems, Rh-POL-2BPY could maintain incredibly outstanding stability for near 400 h owing to the firm coordination bond between Rh and N and high exposed N content in the polymer. Here, POL-2BPY apart from its heat-resisting property acts as massive rivets to immobilize the Rh species in its framework solidly during carbonylation process. XPS, XANES, HAADF-STEM and EXAFS results verify the N species of bipyridine, the single atom dispersion of Rh and Rh-N coordination bond. And above all, the novel five coordinated Rh center is proposed as the real active site of methanol carbonylation by EXAFS spectra. (C) 2018 Elsevier Inc. All rights reserved.