In a word, yes. What you're referring to is sometimes called the "Kenner mission," after Confederate Congressman and extraordinarily wealthy Louisiana planter Duncan Kenner, who championed the idea and was eventually dispatched to Europe to make the offer.

Confederate president Jefferson Davis and Secretary of State Judah P. Benjamin authorized Kenner's mission, which was supposed to be secret. Kenner was authorized to offer gradual emancipation in return for immediate diplomatic recognition - reflecting his, and Benjamin's, belief that the existence of slavery was the factor in Britain, France, and the other great powers declining to formally recognize the Confederacy. The British government was the key here - France, led by Napoleon III, was sympathetic to the Confederacy (seeing it as a counterweight to the Union and a possible source of aid to their beleaguered Mexican adventure), but Napoleon refused to make any major concessions unless Britain also went along first.

The Kenner mission is best understood in the wider political and military context of late 1864-early 1865. The Confederacy was in increasingly dire straits militarily and financially, with Richmond and Petersburg besieged, the Trans-Mississippi cut off, and Sherman moving more or less unchecked through Georgia and later South Carolina. Some Confederates had begun to advocate arming and even freeing enslaved men to fill the ranks. Davis had refused to entertain earlier advocates for this (Gen. Patrick Cleburne being one famous example) because the Confederate Constitution forbade interference with "the right of property in negro slaves." By late 1864, conditions had worsened enough for Davis to change his tune and he and Lee supported proposals to create soldiers out of enslaved men. For the European powers, especially Britain, the appetite for intervention in the Civil War had mostly waned by 1864 (it peaked in the fall of 1862, when the British cabinet actively debated the matter). Union naval and military strength had grown so rapidly that the Admiralty and War Office expressed grave concern over how costly a war with the Union would be. This, combined with tensions in Europe, esp. in Poland and Denmark, turned Palmerston's attentions back to Europe - which he infinitely preferred.

Davis also saw fit to bend his constitutionalism re: Kenner's proposal around this time. He authorized the mission, but concealed it from Congress and the public, although rumors swirled about the mission. Because of the Union blockade, Kenner did not reach Europe for many weeks. Confederate envoy James M. Mason presented a version of the proposal to British Prime Minister Lord Palmerston in March, 1865, and Palmerston firmly declined, on the basis that Confederate failure to win independence on the battlefield, not the presence of slavery, precluded British recognition. Napoleon did the same to Kenner and John Slidell, claiming (truthfully) that slavery had never been an obstacle.

Kenner maintained afterward that if the proposal had been made in 1863, before Gettysburg and Vicksburg, it might have succeeded. We have no way of knowing for sure, but it seems exceedingly unlikely that Davis would have authorized such a move at a time when battlefield victory seemed possible, even likely.

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The Kenner episode, for me, is notable for how it highlights the near-delusion of Davis, Benjamin, and other Confederate leaders about how recognition could be achieved and what, even if they did obtain it, benefits it would actually bring. We have a substantial body of scholarship on international law, belligerent rights, warfare, and recognition (see recent works by Laura Benton, Lisa Ford, Martti Koskaniemmi, Kenneth Moss, and others), and nothing in them suggests that recognition was owed to the Confederacy, or that it would come with anything beyond what they already had: belligerent rights. Recognition was (and is) better understood as acknowledgment of independence already gained rather than a device for gaining it. Confederates assumed that recognition would necessarily bring with it intervention, which was what they really wanted: the Royal Navy sweeping away the blockading fleet. By 1865 that ship, if you'll pardon my pun, had sailed.

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References:

Howard Jones, Blue and Gray Diplomacy: A History of Union and Confederate Foreign Relations (UNC Press, 2010).

Bruce Levine, Confederate Emancipation: Southern Plans to Free and Arm Slaves During the American Civil War, (Oxford, 2006).

Craig A. Bauer, "The Last Effort: The Secret Mission of the Confederate Diplomat, Duncan F. Kenner" Louisiana History 22, no. 1 (1981)

Kenneth Bourne, Britain and the Balance of Power in North America, 1815-1908 (Univ. of California Press, 1967). This is an older work but no one has written anything to surpass it in terms of depth or breadth.

David Krein, The Last Palmerston Government, (Iowa State Univ. Press, 1978)