We can check map key using "CONTAINS" Formula method on Visualforce page

Sample Code

VisualForce Page

<apex:page standardController="Account" recordSetVar="account" extensions="MapkeyExample">
    <apex:pageBlock>
        <apex:pageBlockTable value="{!Account}" var="acc">
            <apex:column headerValue="Account Name">
                <apex:outputLabel value="{!acc.name}"></apex:outputLabel>
                <apex:pageBlockTable rendered="{!IF(CONTAINS(ChkMapKey,acc.name),true,false)}" value="{!accMap[acc.name]}" var="ss">\
                    <apex:column headerValue="Child Map value" value="{!ss}" />
                </Apex:pageBlockTable>
            </apex:column>
        </Apex:pageBlockTable>
    </apex:pageBlock>
</apex:page>

Apex Class

public class MapkeyExample
{
    public string ChkMapKey{get;set;}
    public map < string, string > accMap{get;set;}
    public MapkeyExample(ApexPages.StandardSetController controller)
    {
        accMap = new map < string, string >{'test' => '1', 'test account' => '2', 'C' => '3', 'D' => '4', 'E' => '5', 'F' => '6'};
        ChkMapKey = string.valueof(accMap.keyset()).replace('{', '').replace('{', '');
    }
}

In above code i have created following things:
1. Test Account
2. ChkMapKey String propeerty
3. accMap Map.