Sophie Tanno and Lauren Said-Moorhouse, CNN

Catherine, Princess of Wales, delighted at the 2022 Earthshot Prize awards Friday evening, showcasing her sustainable style in a rented gown and accessorizing with an emerald choker once famously worn by her late mother-in-law, Diana.

The emerald and diamond, art deco-style choker was a firm favorite of the late Diana, Princess of Wales, who daringly once wore it across her forehead as a headband during a 1985 tour of Australia with her then-husband Prince Charles. The piece of jewelry had been loaned to Diana by Queen Elizabeth II.

Kate paired the choker with a vibrant green off-the-shoulder Solace London gown rented for £74 ($90) from online platform HURR for the grand finale of a three-day royal trip to the US.

Prince William founded the Earthshot Prize back in 2020 in the hope of harnessing the world's smartest minds to confront some of the most pressing environmental challenges facing humanity. Each year for the next decade, five winners will receive £1 million (around $1.12 million) to scale up their creative solutions.

The event staged this year in Boston was one of the highlights of the Prince of Wales' calendar and had been dubbed the future King's "World Cup" moment by Hannah Jones, the prize's chief executive officer.

Speaking during the ceremony, William said: "I believe that the Earthshot solutions you have seen this evening prove we can overcome our planet's greatest challenges. And by supporting and scaling them we can change our future.

"Alongside tonight's winners and finalists, and those to be discovered over the years to come, it's my hope the Earthshot legacy will continue to grow, helping our communities and our planet to thrive."

Sustainability was considered by Earthshot organizers in almost every aspect of the night. In a bid to make the occasion as eco-conscious as possible, all food served was plant-based and single-use plastic was banned, guests were transported to the venue in electric or hybrid vehicles, and a focus was put on hiring local crews and equipment.

Like Kate's wardrobe choices, those hitting the green carpet were encouraged to dress in vintage ensembles or wear outfits they would recycle in the future.

Meanwhile, the recycled green carpet -- which had previously been used at the inaugural awards in London last year -- was adorned with plants grown within 100 miles of the venue which would be donated to community organizations following the glitzy event.

Celebrities at the awards ceremony included Hollywood actor Rami Malek and former England football captain David Beckham while artists performing on the night included Annie Lennox, Ellie Goulding and Beyoncé proteges Chloe x Halle.

Chatting with CNN before the event, Malek commended William launching the prize and creating a positive approach to tackling the climate crisis.

"It's extraordinarily inspiring. He is finding answers and the £1 million that are given to these five people, these five organizations, is something that keeps us from looking at the gloom and doom and the pessimism of it all, and looking toward the future of what we can come to do because when we put our ideas together, we can do extraordinary things," said the 41-year-old "Bohemian Rhapsody" star who later presented the Fix Our Climate award.

The awards ceremony capped a challenging visit by the royal couple to Boston, which has been overshadowed by the race controversy that saw a woman identified as William's godmother Susan Hussey in British media reports resign as a royal aide after she repeatedly questioned a prominent Black British-born domestic abuse charity boss about where she "really came from."

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CNN's Carolyn Sung contributed to this report.