Metalloporphyrin Two-Dimensional Polymers via Metal-Catalyst-Free C–C Bond Formation for Efficient Catalytic Hydrogen Evolution

Abstract

A sensible design plays a pivotal role in developing new two-dimensional polymers. Recent years have witnessed many such potential ways utilizing boraxine, imine, phenazine, and C–C linkages, etc., in this direction. However, a metal catalyst-free direct C–C bond remains unexplored in two-dimensional polymer synthesis. Herein, we report an octahydroxy decorated metalloporphyrin based C–C bond linked two-dimensional polymer, synthesized via a metal-catalyst-free route. As a simple strategy, refluxing monomer porphyrin and squaric acid resulted in the formation of freestanding polymer films with crystalline layered morphology. The effect of the central metal ion in tuning H2 evolution is investigated with the finding that a bimetallic (Co and Ni) porphyrin polymer significantly enhanced the performance leading to 670 μmol of H2 generation. The overpotential (105 mV), Tafel slope (74.1 mV/decade), and Faradaic efficiency (97%) testify to efficiency nearly equivalent to that of Pt/C. The overall performance and stability of polymer displays the excellence of a new catalyst design.