Herein, we report a fine-tuning of the two-dimensional alkali–pyridyl coordination assemblies facilely realized by surface reaction between tetrapyridyl-porphyrin molecules and alkali halides on Ag(111) under a solventless ultrahigh vacuum condition. High-resolution scanning tunneling topography and X-ray photoelectron spectra reveal the formation of alkali–pyridyl coordination and the induced conformational tuning of the porphyrin macrocycle cores. Furthermore, employing other different alkali halide substitutes, we demonstrate a fine-tuning of the metal–organic nanostructures at the sub-Å scale. Postdeposition of Fe onto the as-formed precursor layer yields a two-dimensional bimetallic framework structure, manifesting a functionalization of the metal–organic interfaces.