Exhibit 4.1


 


SPECIMEN UNIT CERTIFICATE


 


NUMBER UNITS U-


 


	
    SEE REVERSE FOR

    CERTAIN

    DEFINITIONS
	ESGEN Acquisition Corporation


 


CUSIP []


 


UNITS CONSISTING OF ONE CLASS A ORDINARY
SHARE AND ONE-HALF OF ONE REDEEMABLE


 


WARRANT TO PURCHASE ONE CLASS A ORDINARY
SHARE


 


THIS CERTIFIES THAT                 
is the owner of                  Units.


 


Each Unit (“Unit”) consists of one (1) Class A
ordinary share, par value $0.0001 per share (“Ordinary Shares”), of ESGEN Acquisition Corporation, a Cayman Islands exempted
company (the “Company”), and one-half (1/2) of one redeemable warrant (each whole warrant, a “Warrant”). Each
Warrant entitles the holder to purchase one (1) Ordinary Share for $11.50 per share (subject to adjustment). Each Warrant will become
exercisable thirty (30) days after the Company’s completion of a merger, share exchange, asset acquisition, share purchase,
reorganization or other similar business combination with one or more businesses (each, a “Business Combination”), and will
expire unless exercised before 5:00 p.m., New York City Time, on the date that is five (5) years after the date on which the Company
completes its initial Business Combination, or earlier upon redemption or liquidation (the “Expiration Date”). The Ordinary
Shares and Warrants comprising the Units represented by this certificate are not transferable separately prior to                
, 2021, unless Citigroup Global Markets Inc. and Barclays Capital Inc. elect to allow earlier separate trading, subject to the
Company’s filing with the Securities and Exchange Commission of a Current Report on Form 8-K containing an audited balance
sheet reflecting the Company’s receipt of the gross proceeds of the initial public offering and issuing a press release announcing
when separate trading will begin. No fractional warrants will be issued upon separation of the Units and only whole warrants are exerciseable.
The terms of the Warrants are governed by a Warrant Agreement, dated as of [●], 2021, between the Company and Continental Stock
Transfer & Trust Company, as Warrant Agent, and are subject to the terms and provisions contained therein, all of which terms
and provisions the holder of this certificate consents to by acceptance hereof. Copies of the Warrant Agreement are on file at the office
of the Warrant Agent at 1 State Street, 30th Floor, New York, New York 10004, and are available to any Warrant holder on written request
and without cost.


 


Upon the consummation of the Business Combination,
the Units represented by this certificate will automatically separate into the Class A Ordinary Shares and Warrants comprising such
Units.


 


This certificate is not valid unless countersigned
by the Transfer Agent and Registrar of the Company.


 


This certificate shall be governed by and construed
in accordance with the internal laws of the State of New York.


 


Witness the facsimile signatures of its duly authorized
officers.


 


	By	 	 	 
	 	Chief Executive Officer	 	Chief Financial Officer


 






     


     


    

 


ESGEN Acquisition Corporation


The Company will furnish without charge to each
unitholder who so requests, a statement of the powers, designations, preferences and relative, participating, optional or other special
rights of each class of shares or series thereof of the Company and the qualifications, limitations or restrictions of such preferences
and/or rights.


 


The following abbreviations, when used in the inscription
on the face of this certificate, shall be construed as though they were written out in full according to applicable laws or regulations:


 


	TEN COM	—	as tenants in common	 	UNIF GIFT 

MIN ACT	—	 	Custodian	 
	 	 	 	 	 	 	 	 	 
	 	 	 	 	 	 	(Cust)	 	(Minor)
	TEN ENT	—	as tenants by the entireties	 	 	 	under Uniform Gifts to Minors Act
	 	 	 	 	 	 	 
	 	 	 	 	 	 	(State)
	JT TEN	—	as joint tenants with right of survivorship and not as tenants in common	 	 	 	 	 	 


 


Additional abbreviations may also be used though
not in the above list.


 






    2


     


    

 


For value received,                 
hereby sells, assigns and transfers unto


 


PLEASE INSERT SOCIAL SECURITY OR OTHER IDENTIFYING
NUMBER OF ASSIGNEE


 


(PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING
ZIP CODE, OF ASSIGNEE)


 


Units represented by the within Certificate, and
do hereby irrevocably constitute and                      appoint                
Attorney to transfer the said Units on the books of the within named Company with full power of substitution in the premises.


 


	Dated	 	 	 
	 	 	 	 
	 	 	 	 
	 	 	 	Notice: The signature to this assignment must correspond with the name as written upon the face of the certificate in every particular, without alteration or enlargement or any change whatever.


 


Signature(s) Guaranteed:


 


	 	 
	THE SIGNATURE(S) MUST BE GUARANTEED BY AN ELIGIBLE GUARANTOR INSTITUTION (BANKS, STOCKBROKERS, SAVINGS AND LOAN ASSOCIATIONS AND CREDIT UNIONS WITH MEMBERSHIP IN AN APPROVED SIGNATURE GUARANTEE MEDALLION PROGRAM, PURSUANT TO S.E.C. RULE 17Ad-15 OR ANY SUCCESSOR RULES).	 


 


In each case, as more fully described in the Company’s final
prospectus dated [●], 2021, the holder(s) of this certificate shall be entitled to receive a pro-rata portion of certain
funds held in the trust account established in connection with the Company’s initial public offering only in the event that (i) the
Company redeems the Ordinary Shares sold in its initial public offering and liquidates because it does not consummate an initial business
combination within the period of time set forth in the Company’s amended and restated memorandum and articles of association, as
the same may be amended from time to time, (ii) the Company redeems the Ordinary Shares sold in its initial public offering in connection
with a shareholder vote to amend the Company’s amended and restated memorandum and articles of association (A) that would
modify the substance or timing of the Company’s obligation to provide holders of the Ordinary Shares the right to have their shares
redeemed in connection with the Company’s initial business combination or to redeem 100% of the Ordinary Shares if the Company
does not complete its initial business combination within the time period set forth therein or (B) with respect to any other provision
relating to the rights of holders of the Ordinary Shares, or (iii) if the holder(s) seek(s) to redeem for cash his, her
or its respective Ordinary Shares in connection with a tender offer (or proxy solicitation, solely in the event the Company seeks shareholder
approval of the proposed initial business combination) setting forth the details of a proposed initial business combination. In no other
circumstances shall the holder(s) have any right or interest of any kind in or to the trust account.


 






    3