The NYPD wants to make sure this cop-killer gets caught – no matter how long it takes.

The department is offering a record $111,500 reward for information leading to the arrest of the coward who gunned down off-duty Brooklyn cop Robert Bolden at Dunne’s Bar & Grille in January 1971.

Officers from Bolden’s old precinct raised the funds to beef up the reward amount to finally get the case solved, officials said.

Bolden’s family is grateful for the reward.

“I never met my grandfather but he is the reason I became a cop,” said the slain officer’s grandson, NYPD Detective John Bolden, who is assigned to Brooklyn’s 78th Precinct.

“Growing up my grandmother and father always told me fond stories about him, how he loved being a police officer, how he loved helping people in the community and how he was always working, even when he was off duty trying to help people,” the 41-year-old detective said.

He said he became a detective eight years ago in the hopes he could one day work on his slain grandfather’s case — “to be able to bring closure to the case and my family.”

Robert Bolden, a US Navy veteran assigned to the 75th Precinct in Brooklyn, was shot to death with a sawed-off shotgun shortly after 10 p.m. on Friday Jan. 22, 1971, while off duty.

The Post reported at the time how a bartender at the popular bar and restaurant at 345 Gold St. asked the officer to intervene with another patron at the bar, who pulled the shotgun out from under his coat and opened fire.

Bolden, a 15-year veteran of the department, returned fire despite being shot. But the wound to his chest proved fatal. Police believe that the gunman may have been part of a group of men that planned a robbery at the bar.

None of the men involved in the altercation, including the gunman, were apprehended.

The record reward, payable upon arrest and conviction of the killer, includes contributions from various agencies and departments, including $25,000 from the NYPD Sergeants Benevolent Association, $10,000 each from the NYPD Police Benevolent Association, the lieutenants and captains unions, state corrections and PBA, the Detectives’ Endowment Association and Cop Shot Inc.

The NYPD is contributing another $7,500, with Crime Stoppers and other agencies chipping in $2,500 each.

Crime Stoppers says it’s planning an all-out blitz by week’s end to get the word out, with a flyer and video to be circulated on social media, and posted throughout the Brooklyn neighborhood where Bolden was shot and killed.

Two years later, P.S. 345, an elementary school at 111 Berriman St. in Bolden’s old precinct formerly called the Liberty School, was renamed the Patrolman Robert Bolden School in his memory.

Anyone with information about Bolden’s death should call Crime Stoppers at 1-800-577-8477 (TIPS).