AbstractIn this work, we introduce a 2D materials family with chemical formula MX₂ (M={As, Sb, Bi} and X={S, Se, Te}) having a rectangular 2D lattice. This materials family has been predicted by systematic ab-initio structure search calculations in two dimensions. Using density-functional theory and many-body perturbation theory, we study the structural, vibrational, electronic, optical, and excitonic properties of the predicted MX₂ family. Our calculations reveal that the predicted SbX₂ and BiX₂ monolayers are stable while the AsX₂ layers exhibit an in-plane ferroelectric instability. All materials display strong excitonic effects and good optical absorption within the infrared-to-visible range. Hence, these monolayers can harvest solar energy and serve in optoelectronics applications. Furthermore, our results indicate that exfoliation of the predicted MX₂ monolayers from their bulk counterparts is experimentally viable.