During the optimization, lattice vector angles and slab thickness were fixed. For the initial adsorption of each receptor on graphene, configurations were set to have maximal ππ stacking between the pyrene rings of the receptors and the graphene layer. Notice that, instead of optimizing the receptors as an isolated system, we directly optimized them within the periodic graphene system to avoid self ππ stacking in the isolated state, which would impede stable adsorption on the graphene surface.