Something that perhaps should be specified: values and morals?
Take, for instance, the Silvan Elves of Mirkwood Forest in JRR Tolkien's Middle Earth. Though there is much animosity between dwarves and elves, Men sort of acted as the middlemen for trade. To the elves, whom had immortality, food, land, a kingdom to protect and were safe, there wasn't much else they desired aside from Wealth and Drink.
Elves very much enjoyed the ores that the dwarves had mined, as did men, and none were immune to the greed that things like gold and other rarities provoked. Elves were fine craftsmen, creating elegant pieces of art, weapons, and furniture from what was traded. Therefore, while elves may not necessarily have monetary value for gold, they may still desire it for artistic, magical, or other needs.
Additionally, the Men of Lake-Town perfected the art of brewing to a degree that these wood elves coveted, which is a feat to bring out the reclusive kingdom.
From lotr wikia
Elves are lovers of wine. As stated, the Elves of Mirkwood get all of their wine from the lake city of Lake-town, and there is never a decrease in demand for it. Likewise, all other Elves of Middle-earth are not easily parted from their various types of local wine. Travelers that come upon their feasts will see that after the wine has been passed around for a while, a dramatic change in the general merry making occurs. When offered other types of alcoholic beverages, such as beer, Elves are not known to decline, for they seem to accept all forms of alcohol. It is even said that an Elf could best a Dwarf in a drinking contest, regardless of the type of drink.
So I'd say this question more comes down to what your wood-elves value.
I would like to point out that it is much more interesting to give any being the depth of weaknesses, as having something as two-dimensional as doesn't like pollutants and are self-sustaining gives you effectively nothing. They would be either be reclusive and value nothing from the outside world, or would desire to conquer it to achieve endless growth in nature. You may want to flesh out the activities they generally enjoy, innate skills, mental acuity, so on and so forth, before asking what they would want in trade, as those plainly lay out and describe what your wood elves would desire in trade, whether they don't like to produce something because of pollutants, but are fine with trading for it, or they don't have the resources available.