Combinatorial enumeration of chemical structures, including isomers is a well-known area of chemical mathematics. . In this work, we have enumerated all possible functional group arrangements for common pore geometries, and developed a fingerprint (represented by a histogram) for characterising the dissimilarity between pore environments based on a quantification of their functional group -functional group (FG-FG) distance distribution. We propose this descriptor to be useful for molecular framework materials, such as MOFs and COFs as well as discrete porous cages such as Metal Organic Polyhedra (MOPs) and porous organic cages.