Yes, there is nothing in the Opportunity Zone rules that restricts your Qualified Opportunity Fund (QOF) from allowing investors who invest with cryptocurrency. Note that the payment would be treated as a contribution of property, and if such contribution is tax-free, the QOF would take a basis in the cryptocurrency that is equal to the investor's basis in the cryptocurrency. This means that the QOF could recognize gain or loss when it disposes of the cryptocurrency. If the QOF is a corporation, the QOF will take this gain/loss into its own income; if the QOF is treated as a partnership for tax purposes, this gain/loss should be allocated back to the investor who contributed the cryptocurrency. There is no obligation for you to pay your investors in cryptocurrency.