John G Langan Form 3 Versum Materials / John G Langan ownership change

                               POWER OF ATTORNEY

     Know all by these presents that John G. Langan does hereby make, constitute
and appoint Michael W. Valente and Scott J. Depta as true and lawful
attorneys-in-fact of the undersigned with full powers of substitution and
revocation, for and in the name, place and stead of the undersigned (in the
undersigned's individual capacity), to execute and deliver such forms that the
undersigned may be required to file with the U.S. Securities and Exchange
Commission as a result of the undersigned's ownership of or transactions in
securities of Versum Materials, Inc. (i) pursuant to Section 16(a) of the
Securities Exchange Act of 1934, as amended, including without limitation,
statements on Form 3, Form 4 and Form 5 (including any amendments thereto) and
(ii) in connection with any applications for EDGAR access codes, including
without limitation the Form ID. The Power of Attorney shall remain in full force
and effect until the undersigned is no longer required to file Forms 3, 4, and 5
with regard to his ownership of or transactions in securities of Versum
Materials, Inc., unless earlier revoked in writing. The undersigned acknowledge
that Michael W. Valente and Scott J. Dupta are not assuming any of the
undersigned's responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934.

                                        By: /s/ John G. Langan
                                            -----------------------------------
                                            John G. Langan

Date: September 28, 2016