The pursuit of sustainable materials with advanced, technologically relevant properties is a crucial endeavour for the scientific community. Materials with the necessary functionalities can be synthesized under extreme conditions -- pressures reaching several megabars and temperatures of thousands of Kelvin. However, their exceptional properties or phase stability often diminish when returned to ambient conditions. Interestingly, strongly covalent materials can be trapped in a metastable state and recovered to ambient conditions. Our recent collaboration with experimental partners demonstrated this for polymeric nitrides (W-N [1]) and carbo-nitrides (C-N [2,3] and X-C-N[4]) phases synthesized at pressures in the 100 GPa range. These phases are particularly noteworthy as they exhibit not only singular exceptional functionalities, but multiple simultaneously, such as combinations of ultra-high incompressibility, wide direct band gaps, piezo-electricity, superconductivity, and high-energy density, which makes them multi-functional materials with significant potential for technical applications. This project aims at computationally exploring finite- and high-temperature properties as well as advanced functionalities of synthesized as well as predicted materials in collaboration with extreme conditions experiments. The obtained knowledge will allow us to find ways to tailer multi-functionalities for specific applications. [1] Liang, ..., Trybel, Laniel (2024). High‐Pressure Synthesis of Ultra‐Incompressible, Hard and Superconducting Tungsten Nitrides. Advanced Functional Materials, 2313819. [2] Laniel, Trybel, et al. (2024). Synthesis of Ultra‐Incompressible and Recoverable Carbon Nitrides Featuring CN4 Tetrahedra. Advanced Materials, 36(3), 2308030. [3] Laniel, Trybel, et al. (2024). High‐Pressure Synthesis of oP28‐C3N4 Recoverable to Ambient Conditions. Advanced Functional Materials, 2416892. [4]Aslandukov, Liang, Ehn, Trybel, et al. (2024). Synthesis of LaCN3, TbCN3, CeCN5, and TbCN5 Polycarbonitrides at Megabar Pressures. Journal of the American Chemical Society, 146(26), 18161-18171.