The discovery of novel properties in twisted bilayer graphene has opened up new avenues of research in physics and materials science, making the twistronics a new research hotspot. In this paper, based on two-dimensional tin-based materials and antimonene monolayers, six types of Sb/SnC two-dimensional van der Waals heterostructures (vdWH) with different interlayer twist angles are constructed, and their optoelectronic properties and applications are studied by first-principles calculations. All modeling and calculations are performed using the density functional theory (DFT) software Quantum-ATK. The results show that the Sb/SnC vdWHs with six different interlayer twist angles have various band gaps, and when the interlayer twist angles are 10.89°, 19.11°, 23.41°, and 30°, the Sb/SnC vdWH exhibit a type-I band edge alignment, while at 8.95° and 13.59°, they present a type-II band structure. The results of the orbital-projected band structures of the Sb/SnC vdWHs reveal that the variation in interlayer twist angles changes the atomic stacking in the heterostructures, thereby modifying orbital coupling and further tuning the electronic structure of the heterostructures. Additionally, the calculated absorption spectra indicate that comparing individual Sb and SnC monolayers with Sb/SnC vdWHs, the latter’s absorption coefficient ris significantly enhanced in the visible light region, and the optical absorption characteristics of the heterostructures with different interlayer twist angles vary markedly. In terms of applications, as materials for solar cells, the Sb/SnC vdWHs with interlayer twist angles of 8.95° and 13.59° exhibit photovoltaic conversion efficiencies of 17.48% and 18.59%, respectively; as photocatalysts for the complete water splitting, the Sb/SnC vdWH with an interlayer twist angle of 8.95° can catalytically decompose water across a pH range of 0–2, while a twist angle of 13.59° confines its catalytic activity to a pH value between 0 and 1. Therefore, Sb/SnC van der Waals heterostructures have special rotation angles and have multifunctional application prospects in the fields of solar energy and photocatalysis. More importantly, our research demonstrates that in addition to traditional methods such as strain, doping, and defects, adjusting the interlayer twist angle provides a new degree of freedom for manipulating the optoelectronic properties of materials.