The District’s apartment boom has prompted a team of developers to buy a 223-unit apartment complex in Southwest Washington in hopes of making it more environmentally sustainable and keeping many of the rents affordable to middle- and low-income residents.

The $35.2 million purchase was backed by the Rose Green Cities Fund, a partnership of Citigroup’s community investment arm, Citi Community Capital, and Jonathan Rose Cos., a New York-based developer of affordable housing. Citi and Rose launched the $75 million fund last year to preserve affordable housing in urban areas.