Pressure-Induced Synthesis and Multistep Dehydrogenative Polymerization of Carbon-Doped PH3 Compounds

Herein, we report the successful high-pressure synthesis of a series of ternary hydrides [(CH4)x(PH3)1-x]2H2 with a variable stoichiometric coefficient x (0.03 ± 0.01 < x < 0.22 ± 0.04), which is achieved by laser irradiation of amorphous red phosphorus in methane-hydrogen mixtures with methane concentrations from 10% to 60%. Raman spectroscopic measurements verify the polymerization of PH3 to P2H4 at ∼10 GPa, across all synthesized [(CH4)x(PH3)1-x]2H2 compounds. Notably, varying methane content exerts no discernible effect on the threshold pressure for this polymerization reaction. Upon complete pressure release to 1 atm, solid residues composed of P4H6 and black phosphorus are observed, which reveals the further polymerization of P2H4 under high pressure. Additionally, the absence of abrupt shifts in the pressure-dependent Raman shift and full width at half-maximum (FWHM) of C-H stretching modes, as well as the polymerized products, which only contain phosphides, collectively proves that CH4 cannot react with CH4\PH3\H2 under high pressure.