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An Fe-based heterogeneous catalyst is an attractive Fenton-like catalyst for phenol synthesis due to many advantages. Nevertheless, it is challenging to control the particle size in various high-loading Fe-based materials, which limits its activity and selectivity. In this work, ultra-small Fe clusters embedded in a 3D porous interconnected open-framework g-C3N4 (denoted FeN x /CCN) were successfully fabricated by the combination of a mechanochemical reaction with one-step pyrolysis. Various characterization results showed that ultra-small Fe clusters with a high loading of 32% were uniformly distributed in the hierarchical porous carbon nitride, which offered an access for faster transportation of charge carriers. Fe sites were probably coordinated with carbon nitride by Fe2+–C N–Fe3+ and Fe–N x bonding. High-density Fe clusters could provide abundant active sites and improve the light absorption and the activating ability of H2O2. By taking advantage of semiconductor functions in combination with a rich porous structure and high-density active sites, the novel Fe cluster catalyst exhibited high activity and stability in phenol synthesis, with a maximum phenol yield of 28.1% in visible light. Combining the experimental results with Fenton chemistry, we proposed a possible photocatalytic reaction mechanism. Our work will give valuable information on the development of active metal cluster nanocatalysts for organic synthesis.

A series of model tests were conducted in this study to investigate the deformation characteristics of geosynthetic-reinforced pile-supported (GRPS) composite foundations under cyclic loading. The effects of the applied load, the number of geogrid layers, and types of piles on the performance of the GRPS composite foundation were studied through 1g physical models of composite foundation with well-planned instrumentation. Furthermore, a numerical fitting method was used to assess the relationship between the foundation settlement and the number of load cycles. The results show that with the increase in the magnitude of cyclic load and the number of load cycles, the settlement of GRPS composite foundations and the strain of the pile and geogrid increased accordingly. Adding rigid piles and increasing the number of geogrid layers both could reduce the settlement of GRPS composite foundations, while adding rigid piles was more effective. The relationship between the foundation settlement and the number of load cycles can be expressed by an exponential regression function. The pile strain varied from place to place that the strain of the upper part of the pile was greater than that of the lower part. The geogrid showed a significant impact on the load transfer mechanism of the composite foundation as the geogrid closer to piles endured larger strain. It is critical to consider the variation of the pile strain and the geogrid strain under cyclic loading in the geotechnical practice of composite foundation. The model test results also suggest that the use of GRPS system can effectively reduce the composite foundation settlement. This paper can provide useful references for developing the theoretical framework and design guides for GRPS composite foundations under cyclic loading.