Achieving high selectivity for a specific peptide sequence amongst the myriad of possibilities is a formidable challenge with enormous potential for the development of next-generation biosensors. Here we demonstrate that MONs confer selectivity through multiple weak interactions with peptides. Three ultrathin MON systems were prepared: ZIF-7 and ZIF-7-NH2 possess similar chemical structures while Hf-BTB-NH2 differs significantly. PD biopanning was exploited to screen a library of 1 × 10 13 possible combinations of 7 amino acids and hence identify the strongest binding peptide sequence for each of the three different MONs. In contrast to previous biopanning studies on MOFs, only a single consensus peptide sequence was identified in each case; this is attributed to the MONs surface comprising only a single facet.