discarded and instead the 0-dimensional barcode the number of sampled points per unit volume is used. This is a simplification that corresponds to discarding the essential intervals in all cases where different connected components of the pore system stay separated during the entire filtration; the 0-dimensional barcodes of connected components are determined by the sampling procedure by construction.

The distance $D_{CS}$ between two materials in the conventional descriptor space is estimated with a normalized euclidean distance of five conventional structural properties with an equal weigh for each: $D_i$ (the diameter of largest included sphere), $D_f$ (the diameter of largest free sphere), $\rho$ (density of a framework), $ASA$ (accessible surface area), and $AV$ (accessible volume).

Similarity in different classes of nanoporous materials {#similarity}
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To illustrate the application of our method to finding similar pore geometries across different classes of nanoporous materials, we consider the following questions.

1.  Are there zeolites that have the same pore geometry as a given MOF?

2.  Are there hypothetical MOFs that are similar to MOFs that have already been synthesized?

3.  Are there materials among the ca. 5000 MOF structures that are deposited in the Cambridge Structural Database ([*6*]{}) that have similar pore structures but 