Optimal bimodal pore networks for heterogeneous catalysis

A practical problem in the rational design of a heterogeneous catalyst is to optimize its structure at all scales. By optimizing the large‐pore network of a bimodal porous catalyst with a given nanoporosity (for example, zeolite or mesoporous catalyst) for the yield of diffusion‐limited first‐order reactions, it is found that catalysts typically benefit from a hierarchical pore network with a broad pore‐size distribution. When comparing the performance of the optimal structures to that of self‐similar, fractal‐like pore hierarchies, it is found that the latter can be made to have the same effectiveness factor as the optimal ones, suggesting that fractal‐like catalysts operate very near optimality, even if their structure is considerably different from that of the true optima. This is useful, because fractal‐like structures have the advantage of being organized in a modular, natural way, potentially easy to reproduce by templating.