Anchoring Metal–Nitrogen\nSites on Porous Carbon\nPolyhedra with Highly Accessible Multichannels for Efficient Oxygen\nReduction

Transition metal–nitrogen-carbon complexes, featuring\nsingle\nmetal atoms embedded in a nitrogen-doped carbon matrix, emerge as\npromising alternatives to traditional platinum-based catalysts, offering\ncost-effectiveness, abundance, and enhanced catalytic performance.\nThis work introduces a novel method for the etching and doping of\nzeolitic imidazolate frameworks (ZIFs) with transition metals, creating\na uniform distribution of secondary metal centers on ZIF surfaces.\nBy disrupting the crystalline symmetry of ZIFs through synthetic defect\nengineering, we gain access to their entire internal volume, creating\nmultichannel pathways. The absorption of metal ions is theoretically\nsimulated, demonstrating their thermodynamically spontaneous nature.\nThe selective removal of defect channels under Lewis acidic conditions,\ninduced by metal ion alcoholysis/hydrolysis, facilitates the introduction\nof metal atoms into ZIF cavities. The resulting single-atom catalyst,\nafter pyrolysis, features a three-dimensional (3D) multichannel structure,\nhigh surface area, and uniformly dispersed metal atoms within the\nN-doped carbon matrix, establishing it as an exceptional catalyst\nfor the oxygen reduction reaction (ORR). Our findings highlight the\npotential of using metal etching in defect-engineered metal–organic\nframeworks (MOFs) for single-atom catalyst preparation, paving the\nway for the next generation of high-performance, cost-effective ORR\ncatalysts in sustainable energy systems.