2. Computational detailsAll the den

2. Computational detailsAll the density functional calculations were performed byCASTEP [30] software available in Materials Studio 7.0. The PerdewBurke-Ernzerhof functional within the framework of generalizedgradient approximation (GGA-PBE) [31] was employed for the geometry optimizations and electronic properties calculations.Grimme's dispersion correction [32] (DFT-D2) was used to includethe weak interactions, which is particularly necessary to accuratelyevaluate the physisorption. The unit cell of g-SiC5 was constructedfollowing P-6 symmetry. A vacuum slab of 20 Å is applied to avoidinteraction from periodical images in neighboring cells. The 2
2supercell (with 24 atoms in total) is adopted for gas adsorption andthe lattice parameter keeps unchanged during the adsorption. Afterthe convergence testing, we chose the 10
10
1 and 4
4
1Monkhorst-Pack k-point grid [33] for the Brillouin zone sampling ofunit cell and 2
2 supercell, respectively. And denser k-point grids(12
12
1) were used for the following electronic calculations onband structure and density of states (DOS). The cutoff energy wasset to be 400 eV for all the calculations. All the structures areoptimized until the convergence of the force on each atom is lessthan 0.02 eV/Å. Spin polarized scheme was included during thecalculations. The Mulliken charge population [34] was assigned forcharge analysis, and Mulliken bond order was assigned for bondorder analysis on the optimized adsorption configurations. Forcomparison, the 4
4 graphene supercell is also modelled for gasadsorption