Inspired by the experimental realization of lattice-porous graphene and mesoporous MXenes, the possibility of lattice-penetrated porous titanium nitride, Ti12N8, was proposed and verified by density functional theory calculations. Stabilities, together with mechanical and electronic characteristics, are investigated and systemically discussed: both pristine and terminated (-O, -F, -OH) Ti12N8 show great thermodynamic and kinetic stabilities; the reduced stiffness introduced by lattice pores makes Ti12N8 better candidates for functional heterojunctions with less lattice mismatch. Subnanometer-sized pores increased the number of potential catalytic adsorption sites, and terminations allowed the band gap of MXene to reach 2.25 eV. Moreover, by changing terminations and introducing lattice channels, Ti12N8 could be expected to be used for different applications: direct photocatalytic water splitting, excellent H2/CH4 and He/CH4 selectivity and admirable HER/CO2RR overpotentials. Such excellent characteristics could provide another possible path for flexible nanodevices with tunable mechanics, electronics and optoelectronics properties.