Metallo-supramolecular polymer engineered porous carbon framework encapsulated stable ultra-small nanoparticles: A general approach to construct highly dispersed catalysts

The development of a general approach for fabricating stable ultra-small heterogeneous nanocatalysts has been intensively pursued. However, issues related to complex synthesis processes and structural stability have restricted their investigation and application. Here we report a facile organometallic conjunction strategy for the large-scale fabrication of porous carbon framework encapsulated highly dispersed sub-3 nm ultra-small nanoparticles (USMNPs@PCF). This methodology is based on the convenient aldol condensation reaction to manufacture a metallo-supramolecular polymer precursor and then consequent annealing to form the target nanocomposite. This technique was successfully applied to the preparation of varieties of USMNPs@PCF, including Fe, Co, Ni, Mo, Ru, Rh, Pd and Pt. As a representative application, the PCF encapsulated sub-3 nm Pd nanoparticles demonstrated remarkable durability and efficiency for chemoselective hydrogenation of nitroarenes to their corresponding anilines under ambient conditions with low catalyst loading. All hydrogenation reactions can complete in 4 min with >99% conversion and >99% chemoselectivity. The turnover frequency (TOF) was up to 11:400 h^-1 for p-nitrophenol. This work provides a general, scalable and economical route for the manufacture of sub-3 nm and highly dispersed nanocomposites, which can be used in many other important fields, such as electrochemistry, energy science and environmental protection.