Functionalized hierarchical porous polymeric monoliths as versatile platforms to support uniform and ultrafine metal nanoparticles for heterogeneous catalysis

Microporous polymer monoliths have demonstrated high robustness, convenient recyclability, effective accessibility and impressive catalytic activity in heterogeneous catalysis when employed as catalyst or catalyst support. However, their synthesis is restricted by complicated synthetic conditions, the use of expensive monomers and inconvenient processing. Hence, the design and development of simple, versatile and low-cost strategy for their synthesis is highly desired. Herein, we report a facile strategy to prepare functionalized hierarchical porous polymeric monoliths via a two-step method i.e., the copolymerization of high internal phase emulsion followed by external knitting. The hierarchical porous structure that consists of interconnected macropores and abundant micro/mesopores was confirmed by SEM and N2 sorption analysis. The highest BET surface area of up to 528 m2g−1 was obtained that, however, was decreased with an increase in the functionality of network adjusted by changing the 4-vinylpyridine functional monomer ratio. Afterwards, the functionalized monoliths were employed as versatile platforms to load metal nanoparticles, which resulted in a uniform dispersion and narrow particle size distribution. By tuning the functionality of the monoliths and an appropriate selection of the reduction method, a decent control over the gold nanoparticle size can be readily achieved. Owing to the hierarchical porous structure and uniformly dispersed ultrafine gold nanoparticle, the monolithic catalysts reveal an outstanding performance in the model reaction of 4-nitrophenol reduction.