The optical properties of (R-ClMBA)2SnI4, (S-ClMBA)2SnI4, and (rac-ClMBA)2SnI4 have been determined by UV-Vis, micro-photoluminescence (μPL), and circular dichroism spectra. Figure c shows the corresponding results. Absorption spectra show narrow optical band edges around 600 nm with a slight red-shift for (rac-ClMBA)2SnI4 compared to the two chiral perovskites. The corresponding optical band gap values have been extracted from the Tauc plots for direct transition (Figure ) and correspond to about 2.12 eV for the two chiral perovskites and 2.08 for the racemic compound. The band gap of the present samples is among the lowest band gap reported so far for a 2D chiral perovskite, being that of lead-containing materials around 2.3-2.8 eV and ~2.55 for the only other tin-based 2D chiral perovskite, namely (R/S-MBA)2SnI4. The circular dichroism, carried out on thin films (Figure ) of (R/S-ClMBA)2SnI4, presents signals in the 400-550 nm range, while (rac-ClMBA)2SnI4 does not show any CD. The CD spectra of the two chiral materials have opposite peaks at the same wavelengths, i.e. ~465 and ~520 nm, with the last one correlating very well with the linear absorption shown in Figure , interpreted as the Cotton effect, indicating that the chiroptical properties arise from the Sn-I inorganic framework (the chiral group has CD signals around 250 nm, see Figure ). From the CD data we calculated the asymmetry factor, gCD, which resulted to be around 1×10 -4 for both enantiomers, in line with the values usually found in 2D chiral perovskites. This value is close to the value we extracted from ref.