A mystery buyer has snapped up Katy Perry’s luxurious, 1,500-square-foot TriBeCa duplex penthouse, which was supposed to be her first marital home with Russell Brand. Sources say the property — which Perry was looking to unload just 18 months after buying it, in the wake of her quickie divorce — was sold for near its $2.75 million asking price. The “Teenage Dream” singer bought it for that same amount back in September 2010. The North Moore Street apartment boasts two bedrooms, two bathrooms, a cherry wood staircase and a south-facing terrace with sweeping city views. While Perry’s multimillion-dollar New York real estate deal was going down, the singer was keeping company across the country with Florence + The Machine guitarist Robert Ackroyd. The two were photographed getting close at the Coachella music festival, where Perry was reportedly introducing him as “her boyfriend.” A UK report Friday said Perry asked the Brit ax man to extend his trip to Los Angeles to be with her.