Pt-loaded nitrogen-doped porous carbon/silica composites derived from Pt complex-immobilized bipyridine-bridged mesoporous organosilica

Bipyridine-bridged periodic mesoporous organosilica (BPy-PMO) has a unique pore wall structure in which 2,2 & PRIME;- bipyridine ligands are densely and regularly arranged in the siloxane network. In this study, we investigated the structural changes in BPy-PMO and Pt complex-immobilized BPy-PMO (Pt-BPy-PMO) caused by thermal treatment at 400-1000 degrees C in nitrogen flow. Nitrogen-doped porous carbon/silica composites with high nitrogen/ carbon ratios (0.08-0.11) and large pore diameter (2.6 nm) were obtained at 800-1000 degrees C. The X-ray photoelectron spectroscopy analysis revealed that the pyrolyzed BPy-PMO contained numerous graphitic nitrogen and carbon species, along with a few oxygenated species. Site-isolated mononuclear PtCl2 complexes formed on the pore surface of BPy-PMO were converted to single-site PtO or PtO2 complexes after heating at 400-600 degrees C. The single-site Pt oxides aggregated to form Pt oxide nanoparticles with diameters of 1-5 nm, along with the formation of a small amount of Pt metal after heating at 800 degrees C. The amount of Pt metal increased significantly after heating at 1000 degrees C. BPy-PMO is a unique precursor and template for the preparation of various metal-nitrogen doped carbon materials.