Wearing denim to work can be achieved by wearing a very dark wash jean. A good silhouette for a work setting is a classic trouser jean. Trouser jeans are fitted at the hip then continue loose through the thigh and then flare slightly out from the knee to the ankle. When these jeans are paired with some nice pumps and a tailored piece like a blazer or nice button up the denim can be work appropriate. Even nice flats and a cardigan can make denim wearable to work if you have a slightly more laid-back job.