We present chemiresistive sensing characteristics of spin-coated thin films of newly synthesized bis-porphyrin molecules that involves anchoring of two porphyrins to a benzene ring at meta positions through ester-linkages. The bis-porphyrin films are very smooth (rms roughness < 2 nm) and exhibit high charge mobility (1.8 cm²/Vs). These films are found to be highly selective to Cl₂ with fast response (3 s) and recovery (~8 min) times, and sensitivity in the 10-500 ppb range varies linearly between 278% and 1370%. However, for concentrations ³1000 ppb, the response becomes irreversible, which is attributed to the chemical reaction between Cl₂ and bis-porphyrin films.