Can Macbook Pro 15' from 2014 support 240hz refresh rate in external monitor?

MacBook Pro (Retina, 15-inch, Mid 2014) - Technical Specifications

Graphics and Video support

• Intel Iris Pro Graphics
• NVIDIA GeForce GT 750M with 2GB of GDDR5 memory and automatic graphics switching
• Dual display and video mirroring: Simultaneously supports full native resolution on the built-in display and up to 2560 by 1600 pixels on up to two external displays, both at millions of colors

• Thunderbolt digital video output
  • Native Mini DisplayPort output
  • DVI output using Mini DisplayPort to DVI Adapter (sold separately)
  • VGA output using Mini DisplayPort to VGA Adapter (sold separately)
  • Dual-link DVI output using Mini DisplayPort to Dual-Link DVI Adapter (sold separately)

• HDMI video output
  • Support for 1080p resolution at up to 60Hz
  • Support for 3840-by-2160 resolution at 30Hz
  • Support for 4096-by-2160 resolution at 24Hz

When you choose to use a "Legacy" Interface, including HDMI, the about 60 Hz "heartbeat" refresh (required for CRT displays) is included in the data supplied. (The complete screen of data that was sent 1/60-th second ago is sent again in its entirety. This makes it very difficult for ANY "Legacy" Interface to get beyond 60 Hz, and often HDMI interfaces cannot attain 60 Hz on Big Displays at all.

DisplayPort family {Mini DisplayPort, Full-Size Displayport} is different. DisplayPort displays have their own internal screen buffer, so there is no need for the "heartbeat" refresh, and it is not provided. When the screen stops changing, a DisplayPort cable goes nearly quiet.

When manufacturers talk about 240 Hz refresh rates, they mean the rate from the internal screen buffer inside the display to the display, not the refresh rate from the computer to the display. If (and only if) you use DisplayPort family interface, you can attain computer-to-display refresh rates that are the highest possible, and may momentarily be higher than 60 Hz.

ThunderBolt is a superset of DisplayPort, so the above discussion about DisplayPort includes Thunderbolt direct connection to a ThunderBolt display.