One of the first families of Big Oil — that of Standard Oil Co. Inc. co-founder John D. Rockefeller — on Monday said its philanthropic fund was swearing off fossil fuels.

The Rockefeller Brothers Fund (RBF), estimated in July to be worth more than $860 million, announced the divestment before the United Nations summit on climate change, scheduled to begin Tuesday in New York City.

The private charitable foundation, established in 1940, “has been working to better align its endowed assets with its mission since 2010, when the board of trustees approved a commitment of up to 10% of the endowment to investments consistent with the foundation’s sustainable development program goals,” the RBF said.

Heir and RBF President Stephen Heintz said divesting from fossil fuels would be in line with John D. Rockefeller’s wishes.

“We are quite convinced that if he were alive today, as an astute businessman looking out to the future, he would be moving out of fossil fuels and investing in clean, renewable energy,” Heintz said.

Initial priorities from the 10% pool were to support “clean energy technologies and other business strategies that advance energy efficiency, decrease dependence on fossil fuels and mitigate the effects of climate change,” according to the RBF. Given its pledge to combating climate change, the fund now has committed to a two-step process to divest from fossil fuels. The “immediate focus” was on coal and oilsands investments, which should be eliminated from the fund to less than 1% by the end of 2014. An “appropriate strategy” is being determined to divest from the remaining fossil fuel investments over the next few years, the board said.

RBF trustee Steven Rockefeller said some companies may have financial problems if they have stockpiled more oil and gas reserves than they may be able to burn without contributing significantly to climate damage. “We see this as having both a moral and economic dimension,” he said.