PITTSBURGH — A Boston developer has bought the landmark downtown Union Trust Building at sheriff’s sale for $14 million.

The Davis Companies said it plans to make a substantial investment in the building, which is on the National Register of Historic Places, but hasn’t decided exactly what to do with the 11-story Gothic structure, much of which is vacant, according to its attorney, David Lampl.

“We are evaluating our purchase of the building, regarding its future use, and hope to make a decision within a month or two,” said Jonathan Davis, the company’s founder and chief executive officer.

Industrialist Henry Clay Frick built the structure in 1915-16 and it opened with 240 shops in a four-floor arcade, topped by seven floors of office space. The building features a stained glass rotunda and an atrium, which some experts believe may limit the options for its future use.

“You don’t find too many office buildings today with holes in the middle of them,” said Edward Shriver, a Pittsburgh architect who is familiar with the building but not involved in the sale. He said that a residential or hotel use seems most likely.

After Frick’s initial vision for the building flopped, he sold it in the 1920s to the Union Trust.

Much of the building is vacant today, save for a sandwich shop and a bank on the first floor, and four floors of offices leased by Siemens Corp.

U.S. Bank foreclosed on the property two years ago against 501 Grant Street Partners — a partnership of Los Angeles investors Gerson Fox and Michael Kamen.