With the rapid popularity of liquid crystal polyesters (LCPs) in 5G chip packaging materials, a large amount of waste LCPs were produced. However, the recycling and reutilization of waste LCPs are rarely investigated so far. Herein, the waste LCPs are calcinated by “controlled carbonization” strategy to produce microporous carbons, showing potential in producing freshwater and electricity based on solar-irradiated photothermal conversion. ZnCl2/NaCl eutectic salts were used to catalyze the dehydration and decarboxylation of LCPs to form aromatic fragments and then construct microporous carbon skeletons. The resultant carbons show high specific surface areas and solar absorption efficiency. They were used to prepare interfacial solar steam evaporators, showing a high evaporation rate of 2.17 kg/m2/h with an the energy conversion efficiency of 97.5% and a high electricity generation with an output power of 0.902 W/m2 under 1 sun irradiation. This work not only provides a feasible approach to the sustainable conversion of low-cost waste LCPs into valuable carbon materials by a “controlled carbonization” strategy, but also gives impetus to the potential of microporous carbons for application in solar freshwater and electricity generation.