<?xml version="1.0" encoding="utf-8"?>
<!--XBRL document created with Toppan Merrill Bridge  11.4.0.1 -->
<!--Based on XBRL 2.1-->
<!--Created on: 8/6/2026 10:30:03 PM-->
<!--Modified on: 8/6/2026 10:30:03 PM-->
<xsd:schema targetNamespace="http://trinseo.com/20260923" attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:dei="http://xbrl.sec.gov/dei/2025" xmlns:deprecated="http://www.xbrl.org/2009/role/deprecated" xmlns:dtr="http://www.xbrl.org/2009/dtr" xmlns:ref="http://www.xbrl.org/2006/ref" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xl="http://www.xbrl.org/2003/XLink" xmlns:us-gaap="http://fasb.org/us-gaap/2025" xmlns:utr="http://www.xbrl.org/2009/utr" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:enum2="http://xbrl.org/2020/extensible-enumerations-2.0" xmlns:net="http://www.xbrl.org/2009/role/net" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:dtr-types="http://www.xbrl.org/dtr/type/2024-01-31" xmlns:xbrldi="http://xbrl.org/2006/xbrldi" xmlns:negated="http://www.xbrl.org/2009/role/negated" xmlns:attributeFormDefault="unqualified" xmlns:xbrli="http://www.xbrl.org/2003/instance" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tse="http://trinseo.com/20260923" xmlns:ecd="http://xbrl.sec.gov/ecd/2025" xmlns:ecd-sub="http://xbrl.sec.gov/ecd-sub/2025" xmlns:rxp="http://xbrl.sec.gov/rxp/2025" xmlns:snj="http://xbrl.sec.gov/snj/2025">
  <xsd:annotation>
    <xsd:appinfo>
      <link:linkbase id="linkbaseId">
        <roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/dei/2025/dei-2025.xsd#di" roleURI="http://xbrl.sec.gov/dei/role/document/DocumentInformation" xmlns="http://www.xbrl.org/2003/linkbase" />
        <roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#PvpDisclosure" roleURI="http://xbrl.sec.gov/ecd/role/PvpDisclosure" xmlns="http://www.xbrl.org/2003/linkbase" />
        <roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#AwardTimingDisclosure" roleURI="http://xbrl.sec.gov/ecd/role/AwardTimingDisclosure" xmlns="http://www.xbrl.org/2003/linkbase" />
        <roleRef xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#InsiderTradingPoliciesProc" roleURI="http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc" xmlns="http://www.xbrl.org/2003/linkbase" />
        <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#IndividualsOnly" />
        <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#PvpAdjustmentsOnly" />
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" />
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" />
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" />
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" />
        <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" />
        <link:arcroleRef arcroleURI="http://www.esma.europa.eu/xbrl/esef/arcrole/wider-narrower" xlink:type="simple" xlink:href="http://www.xbrl.org/lrr/arcrole/esma-arcrole-2018-11-21.xsd#wider-narrower" />
        <link:labelLink xlink:type="extended" xlink:role="http://www.xbrl.org/2003/role/link">
          <loc xlink:type="locator" xlink:href="#tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" xlink:label="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" xmlns="http://www.xbrl.org/2003/linkbase" />
          <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" xlink:to="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember_lbl" xmlns="http://www.xbrl.org/2003/linkbase" />
          <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember_lbl" xml:lang="en-US" xmlns="http://www.xbrl.org/2003/linkbase">This member presents the equity awards adjustments on the fair value of prior-year awards forfeited during fiscal year.</label>
          <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember_lbl" xml:lang="en-US" xmlns="http://www.xbrl.org/2003/linkbase">Fair Value Of Prior Year Awards Forfeited During Fiscal Year [Member]</label>
          <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember_lbl" xml:lang="en-US" xmlns="http://www.xbrl.org/2003/linkbase">Fair value of prior-year awards forfeited during fiscal year</label>
        </link:labelLink>
        <presentationLink xlink:role="http://xbrl.sec.gov/dei/role/document/DocumentInformation" xlink:type="extended" xlink:title="995200 - Document - Document Information" xmlns="http://www.xbrl.org/2003/linkbase" />
        <presentationLink xlink:role="http://xbrl.sec.gov/ecd/role/PvpDisclosure" xlink:type="extended" xlink:title="995410 - Disclosure - Pay vs Performance Disclosure" xmlns="http://www.xbrl.org/2003/linkbase">
          <presentationArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/parent-child" xlink:from="ecd_AllAdjToCompMember_639216522038030799" xlink:to="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember_639216522038030799" order="5" use="optional" preferredLabel="http://www.xbrl.org/2003/role/terseLabel" />
          <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllAdjToCompMember" xlink:label="ecd_AllAdjToCompMember_639216522038030799" />
          <loc xlink:type="locator" xlink:href="#tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" xlink:label="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember_639216522038030799" />
        </presentationLink>
        <presentationLink xlink:role="http://xbrl.sec.gov/ecd/role/AwardTimingDisclosure" xlink:type="extended" xlink:title="995443 - Disclosure - Award Timing Disclosure" xmlns="http://www.xbrl.org/2003/linkbase" />
        <presentationLink xlink:role="http://xbrl.sec.gov/ecd/role/InsiderTradingPoliciesProc" xlink:type="extended" xlink:title="995447 - Disclosure - Insider Trading Policies and Procedures" xmlns="http://www.xbrl.org/2003/linkbase" />
        <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended" xlink:title="Individuals">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllIndividualsMember" xlink:label="ecd_AllIndividualsMember" xlink:title="ecd_AllIndividualsMember" />
          <link:loc xlink:type="locator" xlink:href="#tse_MrBozichMember" xlink:label="tse_MrBozichMember" xlink:title="tse_MrBozichMember" />
          <link:definitionArc xlink:type="arc" xlink:from="ecd_AllIndividualsMember" xlink:to="tse_MrBozichMember" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:title="definition:ecd_AllIndividualsMember To tse_MrBozichMember" order="1" priority="0" />
        </link:definitionLink>
        <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/PvpAdjustmentsOnly" xlink:type="extended" xlink:title="Pay vs Performance Adjustments">
          <link:loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd#ecd_AllAdjToCompMember" xlink:label="ecd_AllAdjToCompMember" xlink:title="ecd_AllAdjToCompMember" />
          <link:loc xlink:type="locator" xlink:href="#tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" xlink:label="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" xlink:title="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" />
          <link:definitionArc xlink:type="arc" xlink:from="ecd_AllAdjToCompMember" xlink:to="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" use="optional" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:title="definition:ecd_AllAdjToCompMember To tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" order="1" priority="0" />
        </link:definitionLink>
      </link:linkbase>
    </xsd:appinfo>
  </xsd:annotation>
  <xsd:import namespace="http://fasb.org/us-gaap/2025" schemaLocation="https://xbrl.fasb.org/us-gaap/2025/elts/us-gaap-2025.xsd" />
  <xsd:import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <xsd:import namespace="http://www.xbrl.org/dtr/type/2024-01-31" schemaLocation="https://www.xbrl.org/dtr/type/2024-01-31/types.xsd" />
  <xsd:import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/dei/2025" schemaLocation="https://xbrl.sec.gov/dei/2025/dei-2025.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/ecd/2025" schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-2025.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/ecd-sub/2025" schemaLocation="https://xbrl.sec.gov/ecd/2025/ecd-sub-2025.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/rxp/2025" schemaLocation="https://xbrl.sec.gov/rxp/2025/rxp-2025.xsd" />
  <xsd:import namespace="http://xbrl.sec.gov/snj/2025" schemaLocation="https://xbrl.sec.gov/snj/2025/snj-2025.xsd" />
  <xsd:element name="MrBozichMember" id="tse_MrBozichMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" id="tse_FairValueOfPriorYearAwardsForfeitedDuringFiscalYearMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
</xsd:schema>
