This work describes crystal and electronic structures of a new class of 2D hybrid organic-inorganic compounds based on AB-stacked diamane. Seven members thereof are considered: methyl-, pyrrolyl-, 1,2,4-triazolyl-, phenyl-, pyridinyl-, and pyrimidinyl-substituted (two isomers) diamane. DFT calculations show that an electronic structure of diamane can be modulated by organic functional groups. The chemically functionalized diamanes are semiconductors with HSE06 electronic bandgaps falling in the range [2.09–4.91] eV. Other means of diamane electronic structure tuning include variation of coverage of a diamane surface by substituents, mixing of substituents and changing their mutual orientation. Based on the obtained results we conclude that the functionalized diamanes may serve as photovoltaic materials operable in Vis and near UV spectral regions. Owing to a similarity of the aromatics-substituted diamanes to low-dimensional hybrid metal halide perovskites with aromatic organic cations the former could be photoluminescent. An enhanced resistance of the investigated materials to water is expected. © 2024 Elsevier Ltd