Complex sentence: At the bulk state, TMDCs are crystal made of layer, which interact between them by Van Der Waals forces, these interactions are weaker than the chemical bonds between the Mo and S in MoS2, for example.
Split into simpler sentences: At the bulk state, TMDCs are crystal made of layers, which coupled by Van Der Waals forces. These interactions are weaker than the chemical bonds between the Mo and S in MoS 2, for example.