In this work, 2-element slot-based frequency reconfigurable (FR) multiple-input-multiple-output (MIMO) antenna design antenna with a very wide-sweep is proposed for dynamic spectrum sharing (DSS) in 5G technologies. FR is achieved using varactor diode with frequency tuning range from 1655 to 2605 MHz. The design is a low profile with planar structure having a single element footprint of 19.5 × 20 mm2. The two slot antenna elements of the MIMO configuration are etched out from a ground (GND) plane of dimensions of 60 × 120 mm2. The proposed antenna is narrow-band and hence it is suitable for RF front-end in the 5G-enabled DSS in cognitive radio (CR) applications.