U.K., April 5 -- Led by new chief executive officer Jane Fraser, who took over on March 1 vowing to achieve net-zero greenhouse gas emissions in financing activities by 2050, New York-based Citigroup Inc. is combining three of its investment-banking groups as part of this sustainability push.

In a memo sent to staff from Tyler Dickson and Manolo Falco - global heads of Citigroup's banking, capital markets and advisory unit - Steve Trauber and Sandip Sen will oversee a new natural resources and clean energy transition group.

Trauber will mainly focus on investment banking, while Sen will oversee corporate-banking relationships.

"Energy transition, structural changes underway in global energy systems to drive toward low and zero carbon so...