Power Digital Infrastructure Acquisition II Corp

The special meeting of the stockholders (the “Special Meeting”) of Power & Digital Infrastructure Acquisition II Corp. (“we,” “us,” “our” or the “Company”) will be held at 10:00 a.m., Central Time, on March 12, 2024 at the offices of Kirkland & Ellis LLP, located at 609 Main Street, Suite 4700, Houston, Texas 77002, and virtually via live webcast athttps://www.cstproxy.com/xpdispacii/2024, or at such other time, on such other date and at such other place to which the meeting may be postponed or adjourned, and will also be held virtually via the internet. While stockholders are encouraged to attend the meeting virtually, you will be permitted to attend the Special Meeting in person at the offices of Kirkland & Ellis LLP. You will be able to attend the Special Meeting online, vote, view the list of stockholders entitled to vote at the Special Meeting and submit your questions during the Special Meeting by visiting https://www.cstproxy.com/xpdispacii/2024. If you do not have internet capabilities, you can listen to the Special Meeting by phone by dialing 1 800-450-7155 (toll-free) within the U.S. and Canada or +1 857-999-9155 (standard rates apply) outside of the U.S. and Canada. When prompted enter the pin number 6435857#. This option is listen-only, and you will not be able to vote or enter questions during the Special Meeting if you choose to participate telephonically. The sole purpose of the Special Meeting is to consider and vote upon the following proposals:

• Proposal No. 1 — The Extension Amendment Proposal — to amend the Company’s amended and restated certificate of incorporation (as the same has been amended prior to the date hereof, the “Certificate”) pursuant to amendments to the Certificate in the form set forth in paragraph 3 of Annex A to the accompanying Proxy Statement (such amendments, collectively, the “Extension Amendment” and, such proposal, the “Extension Amendment Proposal”) to extend the date by which the Company must (1) consummate an initial merger, capital stock exchange, asset acquisition, stock purchase, reorganization or similar business combination with one or more businesses (a “business combination”), (2) cease its operations except for the purpose of winding up if it fails to complete such business combination, and (3) redeem all shares of the Company’s Class A common stock, par value $0.0001 per share (the “Class A common stock”), included as part of the units sold in the Company’s initial public offering (such shares of Class A common stock, the “public shares”) that was consummated on December 14, 2021 (the “IPO”), from March 14, 2024 (the “Current Outside Date”) to April 14, 2024 (such date, the “Extended Date”), and to allow the Company, without another stockholder vote, by resolution of the Company’s board of directors (our “board”), to elect to further extend the Extended Date in one-month increments up to three additional times, until July 14, 2024 (each such additional date, as extended, an “Additional Extended Date”), unless the closing of a business combination shall have occurred prior thereto or such earlier date as determined by our board to be in the best interests of the Company (the “Extension”); and

• Proposal No. 2 — The Adjournment Proposal — to approve the adjournment of the Special Meeting to a later date or dates, if necessary, to permit further solicitation and vote of proxies in the event that there are insufficient votes for, or otherwise in connection with, the approval of the Extension Amendment Proposal (the “Adjournment Proposal” and, together with the Extension Amendment Proposal the “Proposals”). The Adjournment Proposal will only be presented at the Special Meeting if there are not sufficient votes to approve the Extension Amendment Proposal.

The purpose of the Extension Amendment Proposal is to allow us more time to complete our previously announced business combination (the “Montana Business Combination”) with Montana Technologies LLC, a Delaware limited liability company (“Montana”). The Current Outside Date is March 14, 2024. Our board has determined that it is in the best interests of the Company to seek an extension of such date and have our stockholders approve the Extension Amendment Proposal to allow for additional time to hold a special meeting to obtain the stockholder approvals required in connection with the Montana Business Combination and to consummate the Montana Business Combination. Our board currently believes that we may need additional time to complete the Montana Business Combination. Without the Extension, if we are unable to complete the Montana Business Combination on or before March 14, 2024, we

would be precluded from completing our initial business combination and would be forced to liquidate. Accordingly, our board believes that in order for us to potentially consummate the Montana Business Combination, we may need to obtain the Extension. Notwithstanding the foregoing, we may decide to abandon the Extension Amendment Proposal at any time and for any reason prior to filing the Extension Amendment with the Secretary of State of the State of Delaware.

In connection with the Extension Amendment Proposal, holders of public shares (the “public stockholders”) may elect to redeem their public shares if the Extension is implemented (the “Election”), for a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Company’s trust account established in connection with the IPO (the “Trust Account”), including interest not previously released to the Company to pay taxes, divided by the number of then outstanding public shares. An Election can be made regardless of whether such public stockholders vote “FOR” or “AGAINST” the Extension Amendment Proposal and an Election can also be made by public stockholders who do not vote, or do not instruct their broker or bank how to vote, at the Special Meeting. Public stockholders may make an Election regardless of whether such public stockholders were holders as of the record date for the Special Meeting. If the Extension Amendment Proposal is approved and the Extension is implemented, public stockholders who do not make the Election would be entitled to have their shares redeemed for cash if we have not completed our initial business combination by the Extended Date or Additional Extended Date, as applicable. In addition, regardless of whether public stockholders vote “FOR” or “AGAINST” the Extension Amendment Proposal, or do not vote, or do not instruct their broker or bank how to vote, at the Special Meeting, if the Extension is implemented and a public stockholder does not make an Election, they will retain the right to vote on any proposed initial business combination in the future and the right to redeem their public shares at a per-share price, payable in cash, equal to the aggregate amount then on deposit in the Trust Account as of two business days prior to the consummation of such initial business combination, including interest not previously released to the Company to pay taxes, divided by the number of then outstanding public shares, in the event a proposed business combination is completed.

We are not asking you to vote on the Montana Business Combination at this time. We will seek approval of the Montana Business Combination, among other things, at a separate special meeting, which is currently expected to be held on March 8, 2024. If the Extension Amendment Proposal is not approved, we may not be able to complete the Montana Business Combination. We urge you to vote at the Special Meeting regarding the Extension Amendment. The withdrawal of funds from the Trust Account in connection with the Election will reduce the amount held in the Trust Account following the Election, and the amount remaining in the Trust Account may be only a small fraction of the approximately $115,277,497 that was in the Trust Account as of February 16, 2024. In such event, we may need to obtain additional funds to complete an initial business combination, and there can be no assurance that such funds will be available on terms acceptable or at all.

If the Extension Amendment Proposal is not approved or the Extension is not implemented and we do not complete our initial business combination by March 14, 2024, we will: (1) cease all operations except for the purpose of winding up; (2) as promptly as reasonably possible but not more than 10 business days thereafter subject to lawfully available funds therefor, redeem 100% of the public shares, at a per-share price, payable in cash, equal to the quotient obtained by dividing (A) the aggregate amount then on deposit in the Trust Account, including interest not previously released to the Company to pay taxes (less up to $100,000 of such net interest to pay dissolution expenses), by (B) the total number of then issued and outstanding public shares, which redemption will completely extinguish public stockholders’ rights as stockholders (including the right to receive further liquidating distributions, if any), subject to applicable law; and (3) as promptly as reasonably possible following such redemption, subject to the approval of our remaining stockholders and our board in accordance with applicable law, dissolve and liquidate, subject in each case to our obligations under Delaware law to provide for claims of creditors and the requirements of other applicable law.

There will be no redemption rights or liquidating distributions with respect to our warrants, which will expire worthless in the event of our winding up. In the event of a liquidation, the holder of our Class B common stock, par value $0.0001 per share (the “founder shares” and, together with the shares of Class A common stock, the “Common Stock”), including XPDI Sponsor II LLC (our “Sponsor”), will not receive any monies held in the Trust Account as a result of its ownership of our founder shares.

Based upon the amount in the Trust Account as of February 16, 2024, which was approximately $115,277,497, we anticipate that the per-share price at which public shares will be redeemed from cash held in the Trust Account will be approximately $10.87 at the time of the Special Meeting. The closing price of the public shares on the Nasdaq Stock Market LLC (the “Nasdaq”) on February 16, 2024, the most recent practicable closing price prior to the mailing

of this Proxy Statement, was $10.82. We cannot assure stockholders that they will be able to sell their shares in the open market, even if the market price per share is higher than the redemption price stated above, as there may not be sufficient liquidity in our securities when such stockholders wish to sell their shares.

If the Extension Amendment Proposal is approved, the approval will constitute consent for us to (1) remove from the Trust Account an amount (the “Withdrawal Amount”) equal to the number of public shares properly redeemed multiplied by the per-share price, equal to the aggregate amount then on deposit in the Trust Account, including interest not previously released to the Company to pay taxes, divided bythe number of then outstanding public shares and (2) deliver to the holders of such redeemed public shares their pro rata portion of the Withdrawal Amount. The remainder of such funds will remain in the Trust Account and will be available for use by us in connection with consummating an initial business combination on or before the Extended Date or Additional Extended Date, as applicable. Holders of public shares who do not redeem their public shares now will retain their redemption rights and their ability to vote on any initial business combination through the Extended Date or Additional Extended Date, as applicable, if the Extension Amendment Proposal is approved.

Our board has fixed the close of business on February 16, 2024 (the “record date”) as the record date for determining our stockholders entitled to receive notice of and vote at the Special Meeting and any adjournment thereof. Only holders of record of the Common Stock on that date are entitled to have their votes counted at the Special Meeting or any adjournment thereof. On the record date of the Special Meeting, there were 17,795,678 shares of Common Stock outstanding, of which 10,608,178 were shares of Class A common stock and 7,187,500 were shares of Class B common stock. The shares of Class B common stock carry voting rights in connection with the Proposals, and we have been informed by our Sponsor and directors that hold founder shares that they intend to collectively vote all of their founder shares in favor of each of the Proposals.

This Proxy Statement contains important information about the Special Meeting and the Proposals. Please read it carefully and vote your shares.

We will pay for the entire cost of soliciting proxies. We have engaged Morrow Sodali LLC (“Morrow”), to assist in the solicitation of proxies for the Special Meeting. We have agreed to pay Morrow a fee of $25,000. We will also reimburse for reasonable out-of-pocket expenses and will indemnify Morrow and its affiliates against certain claims, liabilities, losses, damages and expenses. In addition to these mailed proxy materials, our directors and officers may also solicit proxies in person, by telephone or by other means of communication. These parties will not be paid any additional compensation for soliciting proxies. We may also reimburse brokerage firms, banks and other agents for the cost of forwarding proxy materials to beneficial owners.

This Proxy Statement is dated February 20, 2024 and is first being mailed to stockholders on or about February 20, 2024.